WO2018056908A1

WO2018056908A1 - Piezoelectric resonator and method of forming the same

Info

Publication number: WO2018056908A1
Application number: PCT/SG2017/050479
Authority: WO
Inventors: Yao Zhu; Nan Wang; Chengliang SUN
Original assignee: Agency For Science, Technology And Research
Priority date: 2016-09-26
Filing date: 2017-09-25
Publication date: 2018-03-29

Abstract

A piezoelectric resonator comprising a piezoelectric layer having a first surface and a second surface opposite the first surface and parallel to the first surface, a first electrode patch and a further first electrode patch over the first surface and coupled to a first electrical signal, a second electrode patch and a further second electrode patch over the first surface and coupled to a second electrical signal, a third electrode patch and a further third electrode patch over the second surface and coupled to a third electrical signal, a fourth electrode patch and a further fourth electrode patch over the second surface and coupled to a fourth electrical signal, wherein the first, further first, second and further second electrode patches are aligned to the third, further third, fourth and further fourth electrode patches respectively, and the piezoelectric resonator comprises one or more through holes from the first surface to the second surface.

Description

PIEZOELECTRIC RESONATOR AND METHOD OF FORMING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of Singapore application No. 10201607986P filed September 26, 2016, the contents of it being hereby incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

[0002] Various aspects of this disclosure relate to a piezoelectric resonator. Various aspects of this disclosure relate to a method of forming a piezoelectric resonator.

BACKGROUND

[0003] Micromechanical resonators, especially piezoelectric micromechanical resonators, are required in various electronic applications, such as wireless communications and sensing. For instance, in wireless communications, the fundamental building blocks may include radio-frequency (RF) front-end filters or oscillators, which are constructed using piezoelectric micromechanical resonators to enhance the reception and transmission of signals or to provide the reference clock signals respectively.

[0004] A key component in radio frequency (RF) front-end filters is the bulk acoustic wave (BAW) resonator. It has the advantage of a high effective electromechanical coupling

2 *

coefficient (k_eff ) which proves an advantage to filter applications by rendering a large bandwidth to the filters constructed. However, the resonant frequency of the BAW resonator can only be tuned by changing the physical thickness of the resonator stack, e.g., depositing and patterning an additional layer to mechanically load the resonator, which reduces design flexibility and increases costs.

[0005] On the other hand, lateral field excited (LFE) resonators, e.g., Lamb wave resonators, can have their resonant frequencies defined by lithographic patterning. Therefore, resonators with different resonant frequencies can be fabricated on the same wafer without any extra loading layer. As a result, the fabrication cost may be reduced. However, LFE resonators may suffer from lower k_eff as compared to their BAW counterparts, bringing new challenges for their application as RF filters. SUMMARY

[0006] Various embodiments may relate to a piezoelectric resonator. The piezoelectric resonator may include a piezoelectric layer having a first surface and a second surface opposite the first surface and parallel to the first surface. The piezoelectric resonator may also include a first electrode patch and a further first electrode patch over the first surface, the first electrode patch and the further first electrode patch configured to be coupled to a first electrical signal. The piezoelectric resonator may additionally include a second electrode patch and a further second electrode patch over the first surface, the second electrode patch and the further second electrode patch configured to be coupled to a second electrical signal. The piezoelectric resonator may further include a third electrode patch and a further third electrode patch over the second surface, the third electrode patch and the further third electrode patch configured to be coupled to a third electrical signal. The piezoelectric resonator may also include a fourth electrode patch and a further fourth electrode patch over the second surface, the fourth electrode patch and the further fourth electrode patch configured to be coupled to a fourth electrical signal.

[0007] The first electrode patch may be aligned to the third electrode patch and the further first electrode patch may be aligned to the further third electrode patch. The second electrode patch may be aligned to the fourth electrode patch and the further second electrode patch may be aligned to the further fourth electrode patch. The piezoelectric layer may include one or more through holes from the first surface to the second surface.

[0008] Various embodiments may provide a method of forming a piezoelectric resonator. The method may include providing a piezoelectric layer having a first surface and a second surface opposite the first surface and parallel to the first surface. The method may also include forming a first electrode patch and a further first electrode patch over the first surface, the first electrode patch and the further first electrode patch configured to be coupled to a first electrical signal. The method may additionally include forming a second electrode patch and a further second electrode patch over the first surface, the second electrode patch and the further second electrode patch configured to be coupled to a second electrical signal. The method may further include forming a third electrode patch and a further third electrode patch over the second surface, the third electrode patch and the further third electrode patch configured to be coupled to a third electrical signal. The method may also include forming a fourth electrode patch and a further fourth electrode patch over the second surface, the fourth electrode patch and the further fourth electrode patch configured to be coupled to a fourth electrical signal.

[0009] The first electrode patch may be aligned to the third electrode patch and the further first electrode patch may be aligned to the further third electrode patch. The second electrode patch may be aligned to the fourth electrode patch and the further second electrode patch may be aligned to the further fourth electrode patch. The piezoelectric resonator may include one or more through holes from the first surface to the second surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:

FIG. i A is a schematic showing a top planar view of a piezoelectric resonator according to various embodiments.

FIG. IB is a schematic showing a bottom planar view of the piezoelectric resonator shown in FIG. 1 A according to various embodiments.

FIG. 1C is a schematic showing a cross-sectional side view of the piezoelectric resonator shown in FIGS. 1A and IB (across line A-A') according to various embodiments.

FIG. ID is a schematic showing another cross-sectional side view of the piezoelectric resonator shown in FIGS. 1A and IB (across line B-B') according to various embodiments. FIG. 2 is a schematic showing a method of forming a piezoelectric resonator according to various embodiments.

FIG. 3A shows a top planar view of a piezoelectric resonator according to various embodiments.

FIG. 3B shows a cross-sectional side view of the piezoelectric resonator (across line A-A' or B-B' as shown in FIG. 3A) according to various embodiments.

FIG. 3C shows a perspective view of the piezoelectric resonator according to various embodiments.

FIG. 4 shows a top planar view of another piezoelectric resonator according to various embodiments.

FIG. 5A is a plot of the simulated magnitude of impedance as a function of frequency showing the simulation results with the annotation of derived effective coupling coefficient value of a square shape resonator with a 2 ^χ 2 electrode patch array along the x direction and y direction according to various embodiments.

FIG. 5B is a plot of the simulated magnitude of impedance as a function of frequency showing the simulation results with the annotation of derived effective coupling coefficient value of a mesh shape resonator with a 2 2 electrode patch array along the x direction and y direction according to various embodiments.

FIG.6 is a schematic showing a top planar view of a piezoelectric resonator according to various embodiments.

FIG.7A is a schematic showing a top planar view of another piezoelectric resonator according to various embodiments.

FIG. 7B is a schematic showing a bottom planar view of the piezoelectric resonator shown in FIG. 7A according to various embodiments.

FIG.8 A is a schematic showing a top planar view of yet another piezoelectric resonator according to various embodiments.

FIG. 8B is a schematic showing a bottom planar view of the piezoelectric resonator shown in FIG. 8A according to various embodiments.

FIG. 8C is a schematic showing a cross-sectional side view of the piezoelectric resonator shown in FIG. 8A (across line A- A') according to various embodiments.

DETAILED DESCRIPTION

[0011] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, and logical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0012] Embodiments described in the context of one of the methods or piezoelectric resonators are analogously valid for the other methods or piezoelectric resonators. Similarly, embodiments described in the context of a method are analogously valid for a piezoelectric resonator, and vice versa. [0013] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and'or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0014] The word "over" used with regards to a deposited material formed "over" a side or surface, may be used herein to mean that the deposited material may be formed "directly on", e.g. in direct contact with, the implied side or surface. The word "over" used with regards to a deposited material formed "over" a side or surface, may also be used herein to mean that the deposited material may be formed "indirectly on" the implied side or surface with one or more additional layers being arranged between the implied side or surface and the deposited material. In other words, a first layer "over" a second layer may refer to the first layer directly on the second layer, or that the first layer and the second layer are separated by one or more intervening layers. Further, in the current context, a layer "over: or "on" a side or surface may not necessarily mean that the layer is above a side or surface. A layer "on" a side or surface may mean that the layer is formed in direct contact with the side or surface, and a layer "over" a side or surface may mean that the layer is formed in direct contact with the side or surface or may be separated from the side or surface by one or more intervening layers.

[0015] The resonator as described herein may be operable in various orientations, and thus it should be understood that the terms "top", "bottom", etc., when used in the following description are used for convenience and to aid understanding of relative positions or directions, and not intended to limit the orientation of the resonator.

[0016] In the context of various embodiments, the articles "a", "an" and "the" as used with regard to a feature or element include a reference to one or more of the features or elements.

[0017] In the context of various embodiments, the term "about" or "approximately" as applied to a numeric value encompasses the exact value and a reasonable variance.

[0018] As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. [0019] FIG. 1A is a schematic showing a top planar view of a piezoelectric resonator according to various embodiments. FIG. I B is a schematic showing a bottom planar view of the piezoelectric resonator shown in FIG. 1A according to various embodiments. FIG. 1C is a schematic showing a cross-sectional side view of the piezoelectric resonator shown in FIGS. 1A and IB (across line A- A') according to various embodiments. FIG. ID is a schematic showing another cross-sectional side view of the piezoelectric resonator shown in FIGS. 1A and IB (across line B-B') according to various embodiments.

[0020] The piezoelectric resonator 100 may include a piezoelectric layer 102 having a first surface and a second surface opposite the first surface and parallel to the first surface. The piezoelectric resonator 100 may also include a first electrode patch 104a and a further first electrode patch 104b over the first surface, the first electrode patch 104a and the further first electrode patch 104b configured to be coupled to a first electrical signal. The piezoelectric resonator 100 may additionally include a second electrode patch i06a and a further second electrode patch 106b over the first surface, the second electrode patch 106a and the further second electrode patch 106b configured to be coupled to a second electrical signal. The piezoelectric resonator may further include a third electrode patch 108a and a further third electrode patch 108b over the second surface, the third electrode patch 108a and the further third electrode patch 108b configured to be coupled to a third electrical signal. The piezoelectric resonator 100 may also include a fourth electrode patch 1 10a and a further fourth electrode patch 110b over the second surface, the fourth electrode patch 110a and the further fourth electrode patch 110b configured to be coupled to a fourth electrical signal.

[0021] With reference to FIG. 1A, a first lateral surface of the first electrode patch 104a may face a first lateral surface of the second electrode patch 106a, and a second lateral surface of the first electrode patch 104a adjoining the first lateral surface of the first electrode patch 104a may face a first lateral surface of the further second electrode patch 106b. A first lateral surface of the further first electrode patch 104b may face a second lateral surface of the second electrode patch 106a adjoining the first lateral surface of the second electrode patch 106a, and a second lateral surface of the further first electrode patch 104b adjoining the first lateral surface of the further first electrode patch 104b may face a second lateral surface of the further second electrode patch 106b adjoining the first lateral surface of the further second electrode patch 106b. However, it may also be envisioned that in various other embodiments, the electrode patches 104a, 104b, 106a, 106b may not be of a square or rectangular shape. In various other embodiments, such as in embodiments wherein the electrode patches 104a, 104b, 106a, 106b are of circular shape or octagonal shape, a second lateral surface of the first electrode patch 104a adjoining the first lateral surface of the first electrode patch 104a may not face a first lateral surface of the further second electrode patch 106b, and a second lateral surface of the further first electrode patch 104b adjoining the first lateral surface of the further first electrode patch 104b may not face a second lateral surface of the further second electrode patch 106b adjoining the first lateral surface of the further second electrode patch 106b.

[0022] With reference to FIG. IB, a first lateral surface of the third electrode patch 108a may face a first lateral surface of the fourth electrode patch 110a, and a second lateral surface of the third electrode patch 108a adjoining the first lateral surface of the third electrode patch 108a may face a first lateral surface of the further fourth electrode patch 110b. A first lateral surface of the further third electrode patch 108b may face a second lateral surface of the fourth electrode patch 1 10a adjoining the first lateral surface of the fourth electrode patch 110a, and a second lateral surface of the further third electrode patch 108b adjoining the first lateral surface of the further third electrode patch 108b may face a second lateral surface of the further fourth electrode patch 110b adjoining the first lateral surface of the further fourth electrode patch 110b. However, it may also be envisioned that in various other embodiments, the electrode patches 108a, 108b, 110a, 110b may not be of a square or rectangular shape. In various other embodiments, such as in embodiments wherein the electrode patches 108a, 108b, 1 10a, 110b are of circular shape or octagonal shape, a second lateral surface of the third electrode patch 108a adjoining the first lateral surface of the third electrode patch 108a may not face a first lateral surface of the further fourth electrode patch 110b, and a second lateral surface of the further third electrode patch 108b adjoining the first lateral surface of the further third electrode patch 108b may not face a second lateral surface of the further fourth electrode patch 1 10b adjoining the first lateral surface of the further fourth electrode patch 110b.

[0023] The first electrode patch 104a may be aligned to the third electrode patch 108a (see FIG. 1C) and the further first electrode patch 104b may be aligned to the further third electrode patch 108b (see FIG. ID). The second electrode patch 106a may be aligned to the fourth electrode patch 110a (see FIG. 1C) and the further second electrode patch 106b may be aligned to the further fourth electrode patch 110b (see FIG. ID). The piezoelectric resonator 110 may include a through hole 1 12 from the first surface to the second surface.

[0024] In other words, the resonator 100 may include an array of electrode patches 104a, 104b, 106a, 106b over a first surface and an array of electrode patches 108a, 108b, 110a, 110b over a second surface aligned to the array of electrodes 104a, 104b, 106a, 106b on the first surface. The first electrode patches 104a, 104b and the second electrode patches 106a, 106b may be arranged inter-digitally in a two-dimensional manner along two directions in a lateral plane on or parallel to the first surface. The third electrode patches 108a, 108b and the fourth electrode patches 110a, 110b may be arranged inter-digitally in a two-dimensional manner along two directions in a lateral plane on or parallel to the second surface. The array may further include a through hole 112 extending from the first surface to the second surface.

[0025] Various embodiments may help to address or mitigate one or more issues associated with conventional devices. Various embodiments may provide a resonator with high coupling coefficient, and/or less spurious modes, while having relatively flexible design, and/or having relatively low fabrication costs.

[0026] In the current context, one electrode patch aligned to another electrode patch may mean that a line drawn through the geometrical center of the one electrode patch and through the layer 102, the line perpendicular to the surface on which the one electrode patch is over, also passes through the geometrical center of the other electrode patch.

[0027] In various embodiments, the through hole 112 may extend from a region on the first surface between the first electrode patch 104a, the further first electrode patch 104b, the second electrode patch 106a and the further second electrode patch 106b (see FIG. 1A) to a region on the second surface between the third electrode patch 108a, the further third electrode patch 108b, the fourth electrode patch 1 10a and the further fourth electrode patch 1 10b (see FIG. IB).

[0028] A region "between" the first electrode patch 104a, the further first electrode patch 104b, the second electrode patch 106a and the further second electrode patch 106b may mean that the region includes an intersection between a first line drawn from a geometrical center of the first electrode patch 104a to a geometrical center of the further first electrode patch 104b, and a second line drawn from a geometrical center of the second electrode patch 106a to a geometrical center of the further second electrode patch 106b. [0029] Similarly, a region "between" the third electrode patch 108a, the further third electrode patch 108b, the fourth electrode patch 110a and the further fourth electrode patch 110b may mean that the region include an intersection between a first line drawn from a geometrical center of the third electrode patch 108a to a geometrical center of the further third electrode patch 108b, and a second line drawn from a geometrical center of the fourth electrode patch 110a to a geometrical center of the further fourth electrode patch 110b.

[0030] It may also be envisioned in other embodiments, the through hole may extend from any other location, such as between two neighbouring electrode patches, on the first surface to a corresponding location, such as between two neighbouring electrode patches, on the second surface. In various embodiments, the piezoelectric resonator 110 may include one or more further through holes to form a plurality of through holes extending from the first surface to the second surface. The plurality of through holes may for instance, extend from a region on the first surface between the first electrode patch 104a, the further first electrode patch 104b, the second electrode patch 106a and the further second electrode patch 106b to a region on the second surface between the third electrode patch 108a, the further third electrode patch 108b, the fourth electrode patch 110a and the further fourth electrode patch 110b.

[0031] While FIGS. 1A-B show that each of the electrode patches 104a, 104b, 106a, 106b, 108a, 108b, 110a, 110b has a square shape, it may also be envisioned that each of the electrode patches 104a, 104b, 106a, 106b, 108a, 108b, 110a, 110b may be of any suitable shape.

[0032] For instance, the first electrode patch 104a may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape. Similarly, the further first electrode patch 104b may have a shape selected from a group consisting a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape.

[0033] The second electrode patch 106a may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape. Similarly, the further second electrode patch 106b may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape.

[0034] The third electrode patch 108a may have a shape selected from a group consisting a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape. Similarly, the further third electrode patch 108b may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape.

[0035] The fourth electrode patch 110a may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape. Similarly, the further fourth electrode patch 110b may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape.

[0036] Further, while FIGS. 1A-B show that the through hole 1 12 is a square shape, it may also be envisioned that the through hole 112 may be of any suitable shape. The through hole may have a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape. [0037] The piezoelectric resonator 100 may also be of any suitable shape. In various embodiments, the piezoelectric resonator 100 may have a shape selected from a substantially rectangular shape, a substantially square shape, a substantially circular shape, a substantially parallelogram shape, a substantially polygonal shape (such as a hexagon or an octagon), and an irregular shape.

[0038] In various embodiments, a distance between the first electrode patch 104a and the second electrode patch 106a may be substantially equal to a distance between the further first electrode patch 104b and the further second electrode patch 106b. In various embodiments, a distance between the first electrode patch 104a and the further second electrode patch 106b may be substantially equal to a distance between the second electrode patch 106a and the further first electrode patch 104b.

[0039] In various embodiments, the distance between the first electrode patch 104a and the second electrode patch 106a may be substantially equal to the distance between the first electrode patch 104a and the further second electrode patch 106b. The distance between the further first electrode patch 104b and the second electrode patch 106a may be substantially equal to the distance between the further first electrode patch 104b and the further second electrode patch 106b.

[0040] In various other embodiments, the distance between the first electrode patch 104a and the second electrode patch 106a may be different from the distance between the first electrode patch 104a and the further second electrode patch 106b. The distance between the further first electrode patch 104b and the second electrode patch 106a may be different from the distance between the further first electrode patch 104b and the further second electrode patch 106b.

[0041] In various embodiments, a distance between the third electrode patch 108a and the fourth electrode patch 110a may be substantially equal to a distance between the further third electrode patch 108b and the further fourth electrode patch 110b. In various embodiments, a distance between the third electrode patch 108a and the further fourth electrode patch 110b may be substantially equal to a distance between the fourth electrode patch 110a and the further third electrode patch 108b.

[0042] In various embodiments, the distance between the third electrode patch 108a and the fourth electrode patch 110a may be substantially equal to the distance between the third electrode patch 108a and the further fourth electrode patch 110b. The distance between the further third electrode patch 108b and the fourth electrode patch 110a may be substantially equal to the distance between the further third electrode patch 108b and the further fourth electrode patch 110b.

[0043] In various other embodiments, the distance between the third electrode patch 108a and the fourth electrode patch 110a may be different from the distance between the third electrode patch 108a and the further fourth electrode patch 110b. The distance between the further third electrode patch 108b and the fourth electrode patch 110a may be different from the distance between the further third electrode patch 108b and the further fourth electrode patch 110b.

[0044] In the current context, a "distance" between one electrode patch and another electrode patch may refer to the distance between the geometrical center of the one electrode patch and the geometrical center of the other electrode patch.

[0045] In various embodiments, a first line passing through a center of the first electrode patch 104a and a center of the second electrode patch 106a may be substantially perpendicular to a second line passing through the center of the first electrode patch 104a and a center of the further second electrode patch 106b. A third line passing through a center of the further first electrode patch 104b and the center of the second electrode patch 106a may be substantially perpendicular to a fourth line passing through the center of the further first electrode patch 104b and the center of the further second electrode patch 106b. The first line (through the center of the first electrode patch 104a and the center of the second electrode patch 106a) may be substantially parallel to the fourth line (through the center of the further first electrode patch 104b and the center of the further second electrode patch 106b). The second line (through the center of the first electrode patch 104a and the center of the further second electrode patch 106b) may be substantially parallel to the third line (through the center of the further first electrode patch 104b and the center of the second electrode patch 106a).

[0046] In various other embodiments, a first line passing through a center of the first electrode patch 104a and a center of the second electrode patch 106a may not be substantially perpendicular to a second line passing through the center of the first electrode patch 104a and a center of the further second electrode patch 106b. A third line passing through a center of the further first electrode patch 104b and the center of the second electrode patch 106a may not be substantially perpendicular to a fourth line passing through the center of the further first electrode patch 104b and the center of the further second electrode patch 106b. The first line (through the center of the first electrode patch 104a and the center of the second electrode patch 106a) may be substantially parallel to the fourth line (through the center of the further first electrode patch 104b and the center of the further second electrode patch 106b). The second line (through the center of the first electrode patch 104a and a center of the further second electrode patch 106b) may be substantially parallel to the third line (through the center of the further first electrode patch 104b and the center of the second electrode patch 106a).

[0047] In various embodiments, a first line passing through a center of the third electrode patch 108a and a center of the fourth electrode patch 110a may be substantially perpendicular to a second line passing through the center of the third electrode patch 108a and a center of the further fourth electrode patch 110b. A third line passing through a center of the further third electrode patch 108b and the center of the fourth electrode patch 110a may be substantially perpendicular to a fourth line passing through the center of the further third electrode patch 108b and the center of the further fourth electrode patch 1 10b. The first line (through the center of the third electrode patch 108a and the center of the fourth electrode patch 110a) may be substantially parallel to the fourth line (through the center of the further third electrode patch 108b and the center of the further fourth electrode patch 110b). The second line (through the center of the third electrode patch 108a and the center of the further fourth electrode patch 110b) may be substantially parallel to the third line (through the center of the further third electrode patch 108b and the center of the fourth electrode patch 110a).

[0048] In various other embodiments, a first line passing through a center of the third electrode patch 108a and a center of the fourth electrode patch 110a may not be substantially perpendicular to a second line passing through the center of the third electrode patch 108a and a center of the further fourth electrode patch 110b. A third line passing through a center of the further third electrode patch 108b and the center of the fourth electrode patch 110a may not be substantially perpendicular to a fourth line passing through the center of the further third electrode patch 108b and the center of the further fourth electrode patch 110b. The first line (through the center of the third electrode patch 108a and the center of the fourth electrode patch 110a) may be substantially parallel to the fourth line (through the center of the further third electrode patch 108b and the center of the further fourth electrode patch 110b). The second line (through the center of the third electrode patch 108a and the center of the further fourth electrode patch 11 Ob) may be substantially parallel to the third line (through the center of the further third electrode patch 108b and the center of the fourth electrode patch 110a).

[0049] In various embodiments, the piezoelectric resonator 100 may further include one or more other first electrode patches over the first surface, the one or more other first electrode patches configured to be coupled to the first electrical signal.

[0050] In various embodiments, the piezoelectric resonator 100 may further include one or more other second electrode patches over the first surface, the one or more other second electrode patches configured to be coupled to the second electrical signal.

[0051] In various embodiments, the first electrode patches and the second electrode patches may be alternately arranged along an axis, such as the x-axis, over the first surface. A first electrode patch may be between two second electrode patches along the axis, and a second electrode patch may be between two first electrode patches along the axis. The first electrode patches and the further second electrode patches may be alternately arranged along a further axis, such as the y-axis, over the first surface. A first electrode patch may be between two further second electrode patches along the further axis, and a further second electrode patch may be between two first electrode patches along the further axis.

[0052] In various embodiments, the piezoelectric resonator 100 may further include one or more other third electrode patches over the second surface, the one or more other third electrode patches configured to be coupled to the third electrical signal.

[0053] In various embodiments, the piezoelectric resonator 100 may further include one or more other fourth electrode patches over the second surface, the one or more other fourth electrode patches configured to be coupled to the fourth electrical signal.

[0054] In various embodiments, the third electrode patches and the fourth electrode patches may be alternately arranged along an axis, such as the x-axis, over the second surface. A third electrode patch may be between two fourth electrode patches along the axis, and a fourth electrode patch may be between two third electrode patches along the axis. The third electrode patches and the further fourth electrode patches may be alternately arranged along a further axis, such as the y-axis, over the first surface. A third electrode patch may be between two further fourth electrode patches along the further axis, and a further fourth electrode patch may be between two third electrode patches along the further axis. [0055] In various embodiments, the piezoelectric substrate 100 may include a first bridge between the first electrode patch 104a and the second electrode patch 106a, and a second bridge between the first electrode patch 104a and the further second electrode patch 106b.

[0056] In various embodiments, the piezoelectric substrate 100 may include a third bridge between the further first electrode patch 104b and the second electrode patch 106a, and a fourth bridge between the further first electrode patch 104b and the further second electrode patch 106b.

[0057] The first bridge may be between the third electrode patch 108a and the fourth electrode patch 110a, and the second bridge may be between the third electrode patch 108a and the further fourth electrode patch 110b. The third bridge may be between the further third electrode patch 108b and the fourth electrode patch 110a, and the fourth bridge may be between the further third electrode patch 108b and the further fourth electrode patch 110b.

[0058] In the current context, a "bridge" may be a portion of the piezoelectric layer 102 (in which there is no electrode formed over) connecting a first portion of the piezoelectric layer 102 in which electrodes are formed over, and a second portion of the piezoelectric layer 102 in which electrodes are formed over.

[0059] The piezoelectric layer 102 may include any suitable piezoelectric material. The piezoelectric layer 102 may include a piezoelectric material selected from a group consisting of aluminium nitride (A1N), scandium doped aluminium nitride (ScAIN), aluminium nitride with any other dopant, zinc oxide (ZnO), lead zirconate titanate (PZT), gallium nitride (GaN), lithium niobate (LiNb0₃), lithium tantalite (LiTa0₃), quartz, barium strontium titanate (BaSrTi0₄), barium titanate (BaTi0₃), and any combination thereof.

[0060] In various embodiments, the electrode patches 104a, 104b, 106a, 106b, 108a, 108b, 110a, 110b may be formed from any suitable materials such as molybdenum (Mo), aluminum (Al), platinum (Pt), chromium (Cr), tungsten (W), gold (Au), tantalum (Ta), titanium (Ti), silver (Au), copper (Cu), and any combination thereof. In various embodiments, the electrode patches 104a, 104b, 106a, 106b, 108a, 108b, 110a, 110b may be formed from any suitable electrically conductive material The first electrode patch 104a may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The further first electrode patch 104b may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The second electrode patch 106a may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The second further electrode patch 106b may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The third electrode patch 108a may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The further third electrode patch 108b may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The fourth electrode patch 1 10a may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof. The further fourth electrode patch 110b may include a material selected from a group consisting of molybdenum, aluminium, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof.

[0061] In various embodiments, the first electrical signal may be substantially equal to the fourth electrical signal. The first electrical signal and the fourth electrical signal may be provided by a common signal source or may be provided by different signal sources. In various other embodiments, the first electrical signal may be different from the fourth electrical signal.

[0062] In various embodiments, the second electrical signal may be substantially equal to the third electrical signal. The second electrical signal and the third electrical signal may be provided by a common signal source or may be provided by different signal sources. In various other embodiments, the second electrical signal may be different from the third electrical signal.

[0063] In various embodiments, the first electrode patches and/or the second electrode patches may be electrically floated or grounded. In various embodiments, the third electrode patches and/or the fourth electrode patches may be electrically floated or grounded.

[0064] In various embodiments, a polarity of the first electrical signal and/or the fourth electrical signal may be different from or may be same as a polarity of the second electrical signal and/or the third electrical signal. The magnitude of the first electrical signal and/or the fourth electrical signal may be substantially equal to or may be different from the magnitude of the second electrical signal and/or the third electrical signal.

[0065] In various embodiments, the first electrical signal, the second electrical signal, the third electrical signal and the fourth electrical signal may be alternating current (AC) signals. At any point in time, signals applied to neighbouring electrode patches on the same surface or side of the layer 102 may be of opposite polarity, and signals applied to vertically aligned pair of electrode patches on opposing surfaces or sides of the layer 102 may also be of opposite polarity. The AC signals applied to neighbouring electrode patches on the same surface or side of the layer 102 and the AC signals applied to aligned electrode patches on opposing surfaces or sides of the layer 102 may induce movement in the lateral direction and/or vertical direction.

[0066] FIG. 2 is a schematic 200 showing a method of forming a piezoelectric resonator according to various embodiments. The method may include, in 202, providing a piezoelectric layer having a first surface and a second surface opposite the first surface and parallel to the first surface. The method may also include, in 204, forming a first electrode patch and a further first electrode patch over the first surface, the first electrode patch and the further first electrode patch configured to be coupled to a first electrical signal. The method may additionally include forming, in 206, a second electrode patch and a further second electrode patch over the first surface, the second electrode patch and the further second electrode patch configured to be coupled to a second electrical signal. The method may further include forming, in 208, a third electrode patch and a further third electrode patch over the second surface, the third electrode patch and the further third electrode patch configured to be coupled to a third electric signal. The method may also include forming, in 210, a fourth electrode patch and a further fourth electrode patch over the second surface, the fourth electrode patch and the further fourth electrode patch configured to be coupled to a fourth electrical signal.

[0067] The first electrode patch may be aligned to the third electrode patch and the further first electrode patch may be aligned to the further third electrode patch. The second electrode patch may be aligned to the fourth electrode patch and the further second electrode patch may be aligned to the further fourth electrode patch. The piezoelectric resonator may include one or more through holes from the first surface to the second surface. [0068] In other words, a resonator including an array of electrodes on a first surface and an array of electrodes on a second surface aligned to the array of electrodes on the first surface may be formed. The array may further include one or a plurality of through holes extending from the first surface to the second surface.

[0069] For avoidance of doubt, the steps shown in FIG. 2 may not be in sequence. For instance, steps 208 and 210 may occur before or at the same time as steps 204 and 206.

[0070] A first lateral surface of the first electrode patch may face a first lateral surface of the second electrode patch, and a second lateral surface of the first electrode patch adjoining the first lateral surface of the first electrode patch may face a first lateral surface of the further second electrode patch. A first lateral surface of the further first electrode patch may face a second lateral surface of the second electrode patch adjoining the first lateral surface of the second electrode patch, and a second lateral surface of the further first electrode patch adjoining the first lateral surface of the further first electrode patch may face a second lateral surface of the further second electrode patch adjoining the first lateral surface of the further second electrode patch. A first lateral surface of the third electrode patch may face a first lateral surface of the fourth electrode patch, and a second lateral surface of the third electrode patch adjoining the first lateral surface of the third electrode patch may face a first lateral surface of the further fourth electrode patch. A first lateral surface of the further third electrode patch may face a second lateral surface of the fourth electrode patch adjoining the first lateral surface of the fourth electrode patch, and a second lateral surface of the further third electrode patch adjoining the first lateral surface of the further third electrode patch may face a second lateral surface of the further fourth electrode patch adjoining the first lateral surface of the further fourth electrode patch.

[0071] The one or more through holes may extend from a region on the first surface between the first electrode patch, the further first electrode patch, the second electrode patch and the further second electrode patch to a region on the second surface between the third electrode patch, the further third electrode patch, the fourth electrode patch and the further fourth electrode patch.

[0072] The method may further include forming one or more other first electrode patches over the first surface, the one or more other first electrode patches configured to be coupled to the first electrical signal; and one or more other second electrode patches over the first surface, the one or more other second electrode patches configured to be coupled to the second electrical signal.

[0073] The method may also include forming one or more other third electrode patches over the second surface, the one or more other third electrode patches configured to be coupled to the third electrical signal; and one or more other fourth electrode patches over the second surface, the one or more other fourth electrode patches configured to be coupled to the fourth electrical signal.

[0074] FIG. 3A shows a top planar view of a piezoelectric resonator 300 according to various embodiments. FIG. 3B shows a cross-sectional side view of the piezoelectric resonator 300 (across line A- A' or B-B' as shown in FIG. 3 A) according to various embodiments. FIG. 3C shows a perspective view of the piezoelectric resonator 300 according to various embodiments. The resonator 300 may have an irregular shape such as a net shape. For the sake of clarity and to avoid clutter, not all elements of each feature have been labelled. The resonator 300 may include a piezoelectric substrate or layer 302 having a first side and a second side opposite the first side and substantially parallel to the first side, with the distance between the two surfaces defining the thickness of the piezoelectric substrate or layer 302. The thickness of the substrate or layer 302 may be of any suitable value in a range from 0.01 μηι to 500 μηι. Two sets of electrode patches 304, 306, which may be referred to as top electrode patches, may be arranged in a two-dimensional (2D) checkered pattern on or coupled to the first side. Further, two sets of electrode patches 308, 310, referred to as bottom electrode patches, may be arranged in a similar two-dimensional (2D) checkered pattern on or coupled to the second side. The piezoelectric substrate or layer 302 may be between the top electrode patches 304, 306 and the bottom electrode patches 308, 310. The electrode pitch and width may be denoted as "/>" and ' V respectively. The distance between an outer edge of the electrode patch to the edge of the piezoelectric substrate or layer 302 may be denoted as "e". The bottom electrode patches 308, 310 may be aligned vertically with the top electrode patches 304, 306 respectively. Electrode patches 304 and electrode patches 310 may be connected to a first electrical signal and may, for instance, be denoted with a "+" sign. Electrode patches 306 and electrode patches 308 may be connected to an a second electrical signal with a polarity different from that of the first electrical signal and may, for instance, be denoted with a "-" sign. [0075] The positive electrode patches (i.e. electrode patches 304 and 310) and the negative electrode patches (i.e. electrode patches 306 and 308) may be arranged alternating to each other in the x-y plane. For instance, as shown in FIGS. 3A, 3C, on the first side of the substrate 302, electrode patches 304 alternate with electrode patches 306 along the x-axis (i.e. along the A-A' line shown in FIG. 3A) or the j-axis (i.e. along the B-B' line shown in FIG. 3A). Similarly, on the second side of the substrate, electrode patches 308 alternate with electrode patches 310 along the x-axis or the _y-axis. The electrode pitch, the electrode width, and the edge length along the x-axis may be denoted as PA, WA, and βΑ respectively. The electrode pitch, the electrode width, and the edge length along the y-axis may be denoted as PB, WB, and e# respectively.

[0076] The pitch PA may be equal to or may be different from the pitch p_B. Similarly, the width WA may be equal to may be different from the width WB- The edge length may be equal to or may be different from the edge length eg. The portions of the piezoelectric layer or substrate 302 which do not directly couple the adjacent electrodes with different polarities may be removed within the resonator body to form through holes 312, which may increase the resonator coupling coefficient and/or reduce the spurious modes.

[0077] When an alternating current (AC) signal is applied to the electrode patches, the potential difference between the alternating top electrode patches and bottom electrode patches and between the alternating adjacent lateral electrodes may cause mechanical movement in both the thickness direction and the lateral direction (i.e. along x-axis and ^-axis as shown in FIGS. 3A and 3B).

[0078] If the removed areas labeled in FIG. 3 A are filled with solid material, the solid material in tlrese areas may restrict the movement of the areas under and in between the alternating adjacent electrode patches, which may reduce the effective coupling coefficient of the resonator 300. In addition, due to piezoelectric layer discontinuity, spurious modes may be more difficult to arise with selected areas removed. The shape of the resonator body 300 may not necessarily be of conventional rectangle or square shape, but may also be an irregular shape as shown in FIGS. 3A, 3C.

[0079] FIG. 4 shows a top planar view of another piezoelectric resonator 400 according to various embodiments. FIG. 4 shows electrode patches 404, 406 on the piezoelectric layer 402. For the sake of clarity and to avoid clutter, not all elements of each feature have been labelled. While it is not shown in FIG. 4, the resonator 400 may have another two sets of electrodes on the opposing surface of layer 402, similar to resonator 300.

[0080] As shown in FIG. 4, the alternating electrode patches 404, 406 may not necessarily be arranged along the x-axis and _y-axis, but can also along other directions in x-y plane as shown in FIG. 4. The shape of each electrode patch may be, but may not be limited to a square shape, a diamond shape, a circular shape etc.

[0081] FIG. 5 A is a plot of the simulated magnitude of impedance as a function of frequency showing the simulation results with the annotation of derived effective coupling coefficient value of a square shape resonator with a 2 ^χ 2 electrode patch array along the x direction and y direction according to various embodiments. FIG. 5B is a plot of the simulated magnitude of impedance as a function of frequency showing the simulation results with the annotation of derived effective coupling coefficient value of a mesh shape resonator with a 2 2 electrode patch array along the x direction and y direction according to various embodiments. The effective coupling coefficient of 5.9% in FIG. 5 A may be derived from the plot in FIG. 5A, and the effective coupling coefficient of 9.0% in FIG. 5B may be derived from the plot in FIG. 5B.

[0082] The resonators for which the results are shown in FIGS. 5A and 5B may have the same electrode patch pitch, the same electrode patch dimension and the same electrode patch arrangement. The difference between the resonators is FIG. 5A relates to a resonator in which the piezoelectric layer or substrate is of square shape, and FIG. 5B relates to a resonator in which the piezoelectric layer or substrate is of a mesh, i.e. a resonator with a square layer or substrate with some portions removed from the layer or substrate to form the mesh. It may be seen from the simulation that the response in shown in FIG. 5B has a significantly higher coupling coefficient and may be spurious mode free compared to the response shown in FIG. 5A.

[0083] FIG.6 is a schematic showing a top planar view of a piezoelectric resonator 600 according to various embodiments. The piezoelectric resonator 600 may include a piezoelectric layer 602 having a first surface and a second surface opposite the first surface and parallel to the first surface. The piezoelectric resonator 600 may also include a first electrode patch 604a and a further first electrode patch 604b over the first surface, the first electrode patch 604a and the further first electrode patch 604b configured to be coupled to a first electrical signal. The piezoelectric resonator 600 may additionally include a second electrode patch 606a and a further second electrode patch 606b over the first surface, the second electrode patch 606a and the further second electrode patch 606b configured to be coupled to a second electrical signal.

[0084] While not shown in FIG. 6, the piezoelectric resonator 600 may further include a third electrode patch and a further third electrode patch over the second surface, the third electrode patch and the further third electrode patch configured to be coupled to a third electrical signal. The piezoelectric resonator 600 may also include a fourth electrode patch and a further fourth electrode patch over the second surface, the fourth electrode patch and the further fourth electrode patch configured to be coupled to a fourth electrical signal.

[0085] The first electrode patch 604a may be aligned to the third electrode patch and the further first electrode patch 604b may be aligned to the further third electrode patch. The second electrode patch 606a may be aligned to the fourth electrode patch and the further second electrode patch 606b may be aligned to the further fourth electrode patch. The piezoelectric layer 602 may include a plurality of through holes 612 from the first surface to the second surface. While FIG. 6 shows that the through holes 612 are of circular shape, it may be envisioned that the through holes 612 may be of any other suitable shapes.

[0086] FIG.7A is a schematic showing a top planar view of another piezoelectric resonator 700 according to various embodiments. The piezoelectric resonator 700 may include a piezoelectric layer 702 having a first surface and a second surface opposite the first surface and parallel to the first surface. The piezoelectric resonator 700 may also include a first electrode patch 704a and a further first electrode patch 704b over the first surface, the first electrode patch 704a and the further first electrode patch 704b configured to be coupled to a first electrical signal. The piezoelectric resonator 700 may additionally include a second electrode patch 706a and a further second electrode patch 706b over the first surface, the second electrode patch 706a and the further second electrode patch 706b configured to be coupled to a second electrical signal.

[0087] FIG. 7B is a schematic showing a bottom planar view of the piezoelectric resonator 700 shown in FIG. 7A according to various embodiments. The piezoelectric resonator 700 may also include a third electrode patch 708 over the second surface. The piezoelectric layer 702 may include a through hole 712 from the first surface to the second surface. As shown in FIG. 7B, the third electrode patch 708 may not be present at the position of the through hole 712. The third electrode patch 708 may be configured to be coupled to a third electrical signal.

[0088] FIG.8A is a schematic showing a top planar view of yet another piezoelectric resonator 800 according to various embodiments. FIG. 8B is a schematic showing a bottom planar view of the piezoelectric resonator 800 shown in FIG. 8A according to various embodiments. FIG. 8C is a schematic showing a cross-sectional side view of the piezoelectric resonator 800 shown in FIG. 8 A (across line A- A') according to various embodiments.

[0089] The piezoelectric resonator 800 may include a piezoelectric layer 802 having a first surface and a second surface opposite the first surface and parallel to the first surface. The piezoelectric resonator 800 may also include a first electrode patch 804a and a further first electrode patch 804b over the first surface, the first electrode patch 804a and the further first electrode patch 804b configured to be coupled to a first electrical signal. The piezoelectric resonator 800 may additionally include a second electrode patch 806a and a further second electrode patch 806b over the first surface, the second electrode patch 806a and the further second electrode patch 806b configured to be coupled to a second electrical signal. The piezoelectric layer 802 may include a through hole 812 from the first surface to the second surface. The piezoelectric resonator 800 may also include a third electrode patch 808 over the second surface. The third electrode patch 808 may be present at the position of the through hole 812. As shown in FIG. 8C, the third electrode patch may extend parallel to the second surface of the piezoelectric layer to cover the through hole 812. The third electrode patch 808 may be configured to be coupled to a third electrical signal. While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

1. A piezoelectric resonator comprising:

a piezoelectric layer having a first surface and a second surface opposite the first surface and parallel to the first surface;

a first electrode patch and a further first electrode patch over the first surface, the first electrode patch and the further first electrode patch configured to be coupled to a first electrical signal;

a second electrode patch and a further second electrode patch over the first surface, the second electrode patch and the further second electrode patch configured to be coupled to a second electrical signal;

a third electrode patch and a further third electrode patch over the second surface, the third electrode patch and the further third electrode patch configured to be coupled to a third electrical signal; and

a fourth electrode patch and a further fourth electrode patch over the second surface, the fourth electrode patch and the further fourth electrode patch configured to be coupled to a fourth electrical signal;

wherein the first electrode patch is aligned to the third electrode patch and the further first electrode patch is aligned to the further third electrode patch; wherein the second electrode patch is aligned to the fourth electrode patch and the further second electrode patch is aligned to the further fourth electrode patch; and

wherein the piezoelectric resonator comprises one or more through holes from the first surface to the second surface.

2. The piezoelectric resonator according to claim 1, further comprising:

one or more other first electrode patches over the first surface, the one or more other first electrode patches configured to be coupled to the first electrical signal; and one or more other second electrode patches over the first surface, the one or more other second electrode patches configured to be coupled to the second electrical signal.

The piezoelectric resonator according to claim 1, further comprising:

one or more other third electrode patches over the second surface, the one or more other third electrode patches configured to be coupled to the third electrical signal; and

one or more other fourth electrode patches over the second surface, the one or more other fourth electrode patehes configured to be coupled to the fourth electrical signal.

The piezoelectric resonator according to claim 1,

wherein the piezoelectric layer comprises a first bridge between the first electrode patch and the second electrode patch, and a second bridge between the first electrode patch and the further second electrode patch; and wherein the piezoelectric layer comprises a third bridge between the further first electrode patch and the second electrode patch, and a fourth bridge between the further first electrode patch and the further second electrode patch.

The piezoelectric resonator according to claim 4,

wherein the first bridge is between the third electrode patch and the fourth electrode patch, and the second bridge is between the third electrode patch and the further fourth electrode patch; and

wherein the third bridge is between the further third electrode patch and the fourth electrode patch, and the fourth bridge is between the further third electrode patch and the further fourth electrode patch.

The piezoelectric resonator according to claim 1 ,

wherein the first electrode patch has a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape;

wherein the further first electrode patch has a shape selected from a group consisting a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape;

wherein the second electrode patch has a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape;

wherein the further second electrode patch has a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape;

wherein the third electrode patch has a shape selected from a group consisting a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape;

wherein the further third electrode patch has a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape;

wherein the fourth electrode patch has a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape; and

wherein the further fourth electrode patch has a shape selected from a group consisting of a substantially rectangular shape, a substantially square shape, a substantially diamond shape, a substantially parallelogram shape, a substantially circular shape, a substantially elliptical shape, a substantially polygonal shape, and an irregular shape.

7. The piezoelectric resonator according to claim 1,

wherein the piezoelectric substrate comprises a piezoelectric material selected from a group consisting of aluminum nitride, scandium doped aluminum nitride, aluminum nitride with any other dopant, zinc oxide, lead zirconate titanate, gallium nitride, lithium niobate, lithium tantalite, quartz, barium strontium titanate, barium titanate, and any combination thereof.

8. The piezoelectric resonator according to claim 1,

wherein the first electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof; wherein the further first electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof;

wherein the second electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof; wherein the second further electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof;

wherein the third electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof; wherein the further third electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof;

wherein the fourth electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof; and wherein the further fourth electrode patch comprises a material selected from a group consisting of molybdenum, aluminum, platinum, chromium, tungsten, gold, tantalum, titanium, silver, copper, and any combination thereof.

9. The piezoelectric resonator according to claim 1,

wherein the piezoelectric resonator has a shape selected from a substantially rectangular shape, a substantially square shape, a substantially circular shape, a substantially parallelogram shape, and an irregular shape.

10. The piezoelectric resonator according to claim 1,

wherein a distance between the first electrode patch and the second electrode patch is substantially equal to a distance between the further first electrode patch and the further second electrode patch; and

wherein a distance between the first electrode patch and the further second electrode patch is substantially equal to a distance between the second electrode patch and the further first electrode patch.

11. The piezoelectric resonator according to claim 10,

wherein the distance between the first electrode patch and the second electrode patch is substantially equal to the distance between the first electrode patch and the further second electrode patch.

The piezoelectric resonator according to claim 10,

wherein the distance between the first electrode patch and the second electrode patch is different from the distance between the first electrode patch and the further second electrode patch.

13. The piezoelectric resonator according to claim 1,

wherein a distance between the third electrode patch and the fourth electrode patch is substantially equal to a distance between the further third electrode patch and the further fourth electrode patch; and

wherein a distance between the third electrode patch and the further fourth electrode patch is substantially equal to a distance between the fourth electrode patch and the further third electrode patch.

14. The piezoelectric resonator according to claim 15,

wherein the distance between the third electrode patch and the fourth electrode patch is substantially equal to the distance between the third electrode patch and the further fourth electrode patch.

15. The piezoelectric resonator according to claim 15,

wherein the distance between the third electrode patch and the fourth electrode patch is different from the distance between the third electrode patch and the further fourth electrode patch.

16. The piezoelectric resonator according to claim 1 ,

wherein a first line passing through a center of the first electrode patch and a center of the second electrode patch is substantially perpendicular to a second line passing through the center of the first electrode patch and a center of the further second electrode patch;

wherein a third line passing through a center of the further first electrode patch and the center of the second electrode patch is substantially perpendicular to a fourth line passing through the center of the further first electrode patch and the center of the further second electrode patch;

wherein the first line is substantially parallel to the fourth line; and

wherein the second line is substantially parallel to the third line.

17. The piezoelectric resonator according to claim 1, wherein a first line passing through a center of the first electrode patch and a center of the second electrode patch is not substantially perpendicular to a second line passing through the center of the first electrode patch and a center of the further second electrode patch;

wherein a third line passing through a center of the further first electrode patch and the center of the second electrode patch is not substantially perpendicular to a fourth line passing through the center of the further first electrode patch and the center of the further second electrode patch;

wherein the first line is substantially parallel to the fourth line; and wherein the second line is substantially parallel to the third line.

18. The piezoelectric resonator according to claim 1 ,

wherein a first line passing through a center of the third electrode patch and a center of the fourth electrode patch is substantially perpendicular to a second line passing through the center of the third electrode patch and a center of the further fourth electrode patch;

wherein a third line passing through a center of the further third electrode patch and the center of the fourth electrode patch is substantially perpendicular to a fourth line passing through the center of the further third electrode patch and the center of the further fourth electrode patch;

19. The piezoelectric resonator according to claim 1,

wherein a third line passing through a center of the further third electrode patch and the center of the fourth electrode patch is substantially perpendicular to a fourth line passing through the center of the further third electrode patch and the center of the further fourth electrode patch; wherein the first line is substantially parallel to the fourth line; and

wherein the second line is substantially parallel to the third line.

A method of forming a piezoelectric resonator, the method comprising:

providing a piezoelectric layer having a first surface and a second surface opposite the first surface and parallel to the first surface;

forming a first electrode patch and a further first electrode patch over the first surface, the first electrode patch and the further first electrode patch configured to be coupled to a first electrical signal;

forming a second electrode patch and a further second electrode patch over the first surface, the second electrode patch and the further second electrode patch configured to be coupled to a second electrical signal;

forming a third electrode patch and a further third electrode patch over the second surface, the third electrode patch and the further third electrode patch configured to be coupled to a third electrical signal; and

forming a fourth electrode patch and a further fourth electrode patch over the second surface, the fourth electrode patch and the further fourth electrode patch configured to be coupled to a fourth electrical signal;