JP2001217238A - Semiconductor device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve asymmetrical current/voltage characteristics in both positive and negative polarities in a voltage application in a semiconductor device with MIS structure. SOLUTION: This semiconductor device is provided with a conductor layer 14, an insulation layer 13, and a semiconductor 12. The insulation layer 13 is made of a composition that is silicon concentration as compared with silicon dioxide, and has a distribution where the silicon concentration changes from the side of the semiconductor 12 toward the side of the conductor layer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor device used in a semiconductor integrated circuit and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, miniaturization and high integration of semiconductor devices have been rapidly advanced, and accordingly, the types of insulating layers used in devices have been diversified.

Hereinafter, a semiconductor device having a conventional MIS structure will be described with reference to FIG.

FIG. 12A shows a sectional structure of a conventional semiconductor device having a MIS structure.

In FIG. 12A, 11 is a semiconductor substrate made of silicon, 12 is a diffusion layer formed on the semiconductor substrate 11, 15 is an insulating layer made of silicon dioxide, 14
Is a conductor layer as an electrode made of polysilicon having a low resistance by doping impurities.

FIG. 12B shows a distribution state of the silicon concentration in the insulating layer 15 when attention is paid only to the insulating layer 15. In the figure, the vertical axis indicates the concentration of silicon, and the horizontal axis indicates the distance in the depth direction from the interface of the semiconductor substrate 11 to the interface of the conductor layer 14.

In the conventional case, since the insulating layer 15 is made of silicon dioxide alone, the silicon concentration is uniform along the depth direction, and the silicon concentration is lower than that of silicon alone. Therefore, no current flows through the insulating layer 15 when the electric field strength is low.

However, when the diffusion layer 12 is grounded, the conductor layer 1
When a positive voltage is applied to 4 and gradually increased, an FN tunnel current starts to flow in the insulating layer 15 at a certain voltage or more. This characteristic is the same when the conductor layer 14 is grounded and a positive voltage is applied to the diffusion layer 12 (the direction of the current is reversed). The voltage at which the FN tunnel current starts to flow is determined by the thickness of the insulating layer 15.

If the insulating layer 15 has current-voltage characteristics that differ greatly depending on the positive and negative polarities, a tunnel film that can easily extract electrons in only one direction can be formed, and wide application to a flash microcomputer or the like is expected. You.

[0010]

However, FIG.
In the semiconductor device having the conventional configuration shown in (1), since the insulating layer 15 is formed of a simple silicon dioxide film, the current-voltage characteristics cannot be significantly changed depending on the polarity.

An object of the present invention is to provide a semiconductor device having an MIS structure having asymmetric current and voltage characteristics of both positive and negative polarities.

[0012]

In order to solve this problem, a semiconductor device according to the present invention has a MIS structure comprising a conductor layer, an insulating layer, and a semiconductor, wherein the insulating layer is made of silicon rather than silicon dioxide. It is characterized by being composed of a composition having a high concentration, and having a distribution in which the silicon concentration changes from the semiconductor side toward the conductor layer side.

Thus, a semiconductor device having an insulating layer having significantly different current-voltage characteristics for both positive and negative polarities can be obtained.

[0014]

According to a first aspect of the present invention, there is provided a semiconductor device having a MIS structure including a conductor layer, an insulating layer, and a semiconductor, wherein the insulating layer has a silicon concentration richer than that of silicon dioxide. And a distribution in which the silicon concentration changes from the semiconductor side to the conductor layer side.

[0015] In this case, the silicon concentration may be a distribution that continuously increases or decreases from the semiconductor side to the conductor layer as described in claim 2, or the silicon concentration may be varied from the semiconductor side to the conductor layer as described in claim 3. The distribution may increase or decrease in a stepwise manner over a plurality of steps to the side.

According to a fourth aspect of the present invention, in any one of the first to third aspects, a silicon dioxide film is interposed between the semiconductor and the insulating layer. It is.

According to a fifth aspect of the present invention, there is provided a method of forming an insulating layer on a semiconductor using a laughing gas and a silane-based gas, the insulating layer being a composition having a silicon concentration richer than that of silicon dioxide. Forming a conductor layer on the layer.

According to a sixth aspect of the present invention, there is provided a step of forming a silicon dioxide film on a semiconductor, and using a laughing gas and a silane-based gas on the silicon dioxide film so that the silicon concentration is lower than that of silicon dioxide. 7. The method according to claim 5, further comprising the steps of: forming an insulating layer of a rich composition; and forming a conductor layer on the insulating layer. The step of performing
As described, by continuously changing the flow ratio between the laughing gas and the silane-based gas, the silicon concentration in the insulating layer is continuously increased or decreased from the semiconductor side to the conductor layer side, or As described in claim 8, in the step of forming the insulating layer, the flow rate ratio between the laughing gas and the silane-based gas is changed over a plurality of stages in a time-division manner, so that the silicon concentration in the insulating layer is changed from the semiconductor side. It can be increased or decreased stepwise toward the conductor layer side.

According to a ninth aspect of the present invention, there is provided a composition comprising a step of forming a silicon dioxide film on a semiconductor and a step of ion-implanting silicon into the silicon dioxide film to have a silicon concentration richer than that of the silicon dioxide. The method includes a step of forming an insulating layer and a step of forming a conductor layer on the insulating layer.

According to a tenth aspect of the present invention, there is provided a method of forming a silicon dioxide film on a semiconductor, a step of forming an amorphous silicon or polysilicon film on the silicon dioxide film, Ion-implanting silicon into the silicon dioxide film through the silicon film to form an insulating layer that is a composition having a higher silicon concentration than the silicon dioxide film.

According to the eleventh aspect of the present invention, a step of forming a silicon dioxide film on a semiconductor, a step of forming an amorphous silicon or polysilicon film on the silicon dioxide film, and a step of forming the amorphous silicon or polysilicon film Oxidizing the film to form an insulating layer which is a composition having a silicon concentration richer than that of silicon dioxide.

Thus, an insulating layer having asymmetric current-voltage characteristics according to the positive and negative polarities can be obtained.

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIG. 1 and FIG.

FIG. 1A shows a sectional configuration of a semiconductor device according to the first embodiment of the present invention.

In FIG. 1A, reference numeral 11 denotes a semiconductor substrate made of silicon, 12 denotes a diffusion layer, and 13 denotes a diffusion layer.
An insulating layer 14 formed on 2 is a conductor layer as an electrode made of polysilicon whose resistance is reduced by doping impurities.

The insulating layer 13 is made of a composition having a higher silicon concentration than silicon dioxide. For this reason,
Although the insulation is inferior to that of the conventional insulating layer 15 composed of only a silicon dioxide film shown in FIG. 12, the conductivity is high. This is because extra silicon exists in the insulating layer 13 with respect to silicon dioxide, so that the band structure of silicon dioxide changes, and electrons contributing to conduction increase due to the formation of new levels. It is thought to be. Attempting to obtain current-voltage characteristics equivalent to these using only silicon dioxide is equivalent to making the film thickness extremely thin.

FIG. 1B shows a distribution state of the silicon concentration in the insulating layer 13 when attention is paid only to the insulating layer 13.

As can be seen from FIG. 1B, in the case of the first embodiment, the silicon concentration of the insulating layer 13 is
It increases continuously from the side toward the conductor layer 14 side.

As described above, since the concentration of silicon in the insulating layer 13 becomes higher as it approaches the conductor layer 14 side, electrons are easily injected in the direction from the conductor layer 14 to the diffusion layer 12. On the other hand, since the silicon concentration of the insulating layer 13 on the diffusion layer 12 side is low, injection of electrons from the diffusion layer 12 side becomes difficult. Therefore, the current easily flows from the diffusion layer 12 side to the conductor layer 14 side, and the current-voltage characteristics greatly change according to the polarity of the voltage application.

FIG. 2 shows a method of manufacturing a semiconductor device according to the first embodiment of the present invention in the order of steps.

In FIG. 2, first, an impurity is introduced into a semiconductor substrate 11 made of one conductivity type silicon to form a diffusion layer 12.
To form

Next, an insulating layer 13 made of a composition having a silicon concentration richer than that of silicon dioxide is deposited on the diffusion layer 12 by LPCVD using a laughing gas and a silane-based gas.

At this time, as the flow rate ratio of the silane-based gas to the laughing gas is gradually increased, the silicon concentration in the film to be the insulating layer 13 increases continuously.

As a result, as shown in FIG.
The insulating layer 13 whose silicon concentration continuously increases from the second side toward the conductor 14 can be obtained.

After that, the conductor layer 14 is formed on the insulating layer 13.

As described above, according to the first embodiment, the silicon concentration in the insulating layer 13 has a distribution that continuously increases from the diffusion layer 12 side to the conductor layer 14 side. Asymmetric current-voltage characteristics can be realized.

When the flow ratio of the silane gas to the laughing gas is gradually decreased, the silicon concentration in the film to be the insulating layer 13 continuously decreases from the diffusion layer 12 side to the conductor 14 side. Therefore, a semiconductor device having asymmetric current-voltage characteristics opposite to the above description can be realized.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIGS.

FIG. 3A shows a sectional configuration of a semiconductor device according to the second embodiment of the present invention.

In FIG. 3A, reference numeral 11 denotes a semiconductor substrate made of silicon, 12 denotes a diffusion layer, and 13 denotes a diffusion layer.
An insulating layer 14 formed on 2 is a conductor layer as an electrode made of polysilicon whose resistance is reduced by doping impurities.

FIG. 3B shows a distribution state of the silicon concentration in the insulating layer 13 when attention is paid only to the insulating layer 13.

As can be seen from FIG. 3B, in the case of the second embodiment, the silicon concentration of the insulating layer 13 is
It has a distribution that increases stepwise from the side toward the conductor layer 14 over a plurality of steps.

Also in the case of the second embodiment, the first embodiment
Similarly to the case described above, the concentration of silicon gradually increases as approaching the conductor 14 side, so that electrons are easily injected in the direction from the conductor layer 14 to the diffusion layer 12. On the other hand, injection of electrons from the substrate 11 side is not different from the case of a normal oxide film. Therefore, the current-voltage characteristics greatly change according to the polarity of the voltage application.

FIG. 4 shows a method of manufacturing a semiconductor device according to the second embodiment of the present invention in the order of steps.

In FIG. 4, first, an impurity is introduced into a silicon substrate 11 of one conductivity type to form a diffusion layer 12.

Next, an insulating layer 13 made of a composition having a higher silicon concentration than silicon dioxide is deposited on the diffusion layer 12 by LPCVD using a laughing gas and a silane-based gas.

At this time, the LPCVD process is performed in two
When the gas flow ratio is changed in five to five times, the insulating layer 13
The silicon concentration in the film to be formed gradually increases.

As a result, as shown in FIG.
The insulating layer 13 in which the silicon concentration increases stepwise from the second side toward the conductor layer 14 can be obtained.

After that, the conductor layer 14 is formed on the insulating layer 13.

As in the second embodiment, when the LPCVD process is performed two to five times in a time-division manner, the LPCV process is performed by continuously changing the gas components as in the first embodiment. Gas control for depositing the insulating layer 13 can be performed more easily than in the case.

As described above, according to the second embodiment, the silicon concentration in the insulating layer 13 has a distribution that increases stepwise from the diffusion layer 12 side to the conductor layer 14 side in a plurality of steps. Therefore, asymmetric current-voltage characteristics can be realized.

When the flow rate ratio of the silane gas to the laughing gas is gradually reduced, the silicon concentration in the film to be the insulating layer 13 decreases stepwise from the diffusion layer 12 side to the conductor 14 side. Therefore, a semiconductor device having asymmetric current-voltage characteristics opposite to the above description can be realized.

(Embodiment 3) Embodiment 3 of the present invention will be described with reference to FIGS.

FIG. 5A shows a cross-sectional structure of a semiconductor device according to the third embodiment of the present invention.

In FIG. 5A, reference numeral 11 denotes a semiconductor substrate made of silicon, 12 denotes a diffusion layer, and 15 denotes a diffusion layer.
An insulating layer 14 having a silicon concentration richer than that of the silicon dioxide film 15 and having a distribution in which the silicon concentration changes from the diffusion layer 12 side toward the conductor layer 14 side; Is a conductor layer as an electrode made of polysilicon having a low resistance by doping impurities.

That is, the feature of the third embodiment is that the silicon dioxide film 15 formed on the main surface of the semiconductor substrate 11 is formed.
Is interposed between the diffusion layer 12 and the insulating layer 13.

FIG. 5B shows a distribution state of the silicon concentration when attention is paid to the silicon dioxide film 15 and the insulating layer 13.

As can be seen from FIG. 5B, in the case of the third embodiment, the silicon concentration of the insulating layer 13 is
It increases continuously from the side toward the conductor layer 14 side. Moreover, below the insulating layer 13, there is a silicon dioxide film 15 having a lower silicon concentration.

Therefore, the electrons injected from the conductor layer 14 pass through the region of the insulating layer 13 and pass through the silicon dioxide film 15.
Introduced inside. That is, electrons tend to be more easily injected at the interface between the insulating layer 13 and the silicon dioxide film 15 than the normal injection from the conductor layer 14 due to the function of excess silicon in the insulating layer 13. This is considered to be due to the fact that the silicon at the interface of the insulating layer 13 is clustered or the like, so that the electric field concentration tends to occur more easily than the silicon crystal plane. On the other hand, electron injection from the diffusion layer 12 side
Since the silicon dioxide film 15 is in contact with the interface, it becomes difficult to inject electrons. Therefore, the current easily flows from the diffusion layer 12 side to the conductor layer 14 side, and the current-voltage characteristics greatly change according to the polarity of the voltage application.

FIG. 6 shows a method of manufacturing a semiconductor device according to the third embodiment of the present invention in the order of steps.

In FIG. 6, first, an impurity is introduced into a silicon substrate 11 of one conductivity type to form a diffusion layer 12. Next, a silicon dioxide film 15 is first deposited by LPCVD using a laughing gas and a silane-based gas so that the silicon dioxide film 15 is formed.

Thereafter, by gradually increasing the flow rate ratio of the silane-based gas to the laughing gas, the silicon concentration in the film is continuously increased.

As a result, as shown in FIG. 5, an insulating layer 13 whose silicon concentration continuously increases from the diffusion layer 12 side to the conductor 14 side can be formed on the silicon dioxide film 15. .

After that, the conductor layer 14 is formed on the insulating layer 13.

As described above, according to the third embodiment, the insulating layer 13 has a distribution in which the silicon concentration continuously increases toward the conductor layer 14, and the insulating layer 13 has a distribution below the insulating layer 13. Since the silicon dioxide film 15 is present,
It is possible to realize a semiconductor device having more asymmetric current-voltage characteristics than the first and second embodiments.

(Embodiment 4) Embodiment 4 of the present invention will be described with reference to FIG.

The semiconductor device of the fourth embodiment has basically the same structure as that of the third embodiment shown in FIG. A film 15 is formed by sequentially stacking an insulating layer 13 on the silicon dioxide film 15, and the silicon concentration of the insulating layer 13 is
It has a distribution that increases bicontinuously from the two sides to the conductor layer 14 side.

In the fourth embodiment, the manufacturing method for obtaining the semiconductor device having the configuration shown in FIG. 5A is slightly different from that in the third embodiment. Therefore, a method of manufacturing a semiconductor device according to the fourth embodiment will be described in detail below.

FIG. 7 shows a method of manufacturing a semiconductor device according to the fourth embodiment of the present invention in the order of steps.

In FIG. 7, first, a diffusion layer 12 is formed by introducing impurities into a silicon substrate 11 of one conductivity type. Next, first, a silicon dioxide film 15 is formed by an LPCVD method using a laughing gas and a silane-based gas or by thermal oxidation.

Subsequently, extra silicon is introduced into silicon dioxide film 15 by ion-implanting silicon from above silicon dioxide film 15, and the silicon concentration in silicon dioxide film 15 changes continuously. To do. In this case, asymmetry in the layer direction of the silicon concentration results in asymmetry due to the polarity of the current-voltage characteristic, and therefore, a peak of the silicon concentration comes near the interface between the silicon dioxide film 15 and the conductor layer 14 after the ion implantation. As described above, it is desirable to perform very shallow implantation with low implantation energy.

In this manner, as shown in FIG. 5A, a part of the silicon dioxide film 15 remains on the diffusion layer 12 side, and the silicon concentration is continuously changed from the middle of the film to the conductor layer 14 side. Can be obtained.

After that, the conductor layer 14 is formed on the insulating layer 13.

As described above, according to the fourth embodiment, the insulating layer 13 has a distribution in which the silicon concentration continuously increases toward the conductor layer 14, and the insulating layer 13 has a distribution below the insulating layer 13. Since the silicon dioxide film 15 is present,
It is possible to realize a semiconductor device having more asymmetric current-voltage characteristics than the first and second embodiments.

By properly setting the ion implantation energy for the silicon dioxide film 15, FIG.
As shown in FIG. 5, the insulating layer 13 in which the silicon concentration is richer than silicon dioxide without leaving the silicon dioxide film 15 as it is and the silicon concentration continuously increases from the diffusion layer 12 side to the conductor layer 14 side. It is also possible to form

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIGS.

FIG. 8A shows a sectional structure of a semiconductor device according to the third embodiment of the present invention.

In FIG. 8A, reference numeral 11 denotes a semiconductor substrate made of silicon, 12 denotes a diffusion layer, and 13 denotes a silicon concentration richer than that of silicon dioxide and the silicon concentration increases from the diffusion layer 12 side to the conductor layer 14 side. The insulating layer 16 has an increasing distribution toward the surface, 16 is an amorphous silicon film formed on the insulating layer 13, and 14 is a conductor layer as an electrode made of polysilicon doped with impurities to reduce the resistance.

That is, the feature of the fifth embodiment is that the amorphous silicon film 1 is provided between the insulating layer 13 and the conductor layer 14.
6 is interposed.

FIG. 8B shows a distribution state of the silicon concentration when attention is paid to the insulating layer 13 and the amorphous silicon film 16.

As can be seen from FIG. 8B, in the case of the fifth embodiment, the silicon concentration of the insulating layer 13 is
It increases continuously from the side toward the conductor layer 14 side. Moreover, an amorphous silicon film 16 having a high silicon concentration exists above the insulating layer 13.

For this reason, the concentration of silicon becomes higher as approaching the conductor layer 14 side, so that more electrons are generated in the direction from the conductor layer 14 to the diffusion layer 12 than in the first to third embodiments. It becomes easy to be injected. On the other hand, since the silicon concentration of the insulating layer 13 on the diffusion layer 12 side is low, injection of electrons from the diffusion layer 12 side becomes difficult. Therefore, the current easily flows from the diffusion layer 12 side to the conductor layer 14 side, and the current-voltage characteristics greatly change according to the polarity of the voltage application.

FIG. 9 shows a method of manufacturing a semiconductor device according to the fifth embodiment of the present invention in the order of steps.

In FIG. 9, first, a diffusion layer 12 is formed by introducing an impurity into a silicon substrate 11 of one conductivity type. Next, a silicon dioxide film 15 is formed on the diffusion layer 12 by LPCVD or thermal oxidation.

Subsequently, a polysilicon film 16 is deposited on the silicon dioxide film 15 by the LPCVD method.

Next, silicon is ion-implanted from the polysilicon film 16 to the silicon dioxide film 15 to introduce extra silicon into the silicon dioxide film 15 so that the silicon concentration in the silicon dioxide film 15 is continuously increased. Let it change. In this case, the asymmetry of the silicon concentration in the layer direction results in the asymmetry due to the polarity of the current-voltage characteristic, so that the peak of the silicon concentration near the interface between the silicon dioxide film 15 and the amorphous silicon film 16 after ion implantation. Adjust the implantation energy to achieve

In this way, as shown in FIG. 8A, it is possible to obtain the insulating layer 13 whose silicon concentration continuously increases from the diffusion layer 12 side to the amorphous silicon film 16 side.

After that, the conductor layer 14 is formed on the insulating layer 13.

As described above, according to the fifth embodiment, insulating layer 13 has a distribution in which the silicon concentration continuously increases toward conductor layer 14 side, and Since the amorphous silicon film 16 is present, electrons are more easily injected in the direction from the conductor layer 14 to the diffusion layer 12 than in the first to third embodiments, and the semiconductor device has a remarkable asymmetric current-voltage characteristic. Can be realized.

In the above description, the amorphous silicon film 16 is formed on the silicon dioxide film 15 in the manufacturing process shown in FIG. 9, but a polysilicon film may be used instead of the amorphous silicon film 16. Good.

In the fifth embodiment, the insulating layer 13
All have a silicon concentration richer than that of silicon dioxide, but by appropriately adjusting the ion implantation energy for the silicon dioxide film 15,
The second side is silicon dioxide, and it is possible to form the insulating layer 13 in which the silicon concentration continuously increases from the middle of the film to the amorphous silicon film 16 side.

Embodiment 6 Hereinafter, Embodiment 6 of the present invention will be described with reference to FIG. 10 and FIG.

FIG. 10A shows a cross-sectional structure of a semiconductor device according to the sixth embodiment of the present invention.

In FIG. 10A, reference numeral 11 denotes a semiconductor substrate made of silicon, 12 denotes a diffusion layer, 15 denotes a silicon dioxide film formed on the diffusion layer 12, and 13 denotes a silicon concentration higher than that of the silicon dioxide film 15. Is rich, and the silicon concentration has a distribution in which the silicon concentration decreases from the diffusion layer 12 side to the conductor layer 14 side; 16 is an amorphous silicon film formed on the insulating layer 13; This is a conductor layer as an electrode made of low-resistance polysilicon.

That is, the feature of the fifth embodiment is that the insulating layer 13 is provided on the silicon dioxide film 15 and the silicon concentration distribution of the insulating layer 13 is
It is increasing toward 5.

FIG. 10B shows a distribution state of the silicon concentration when attention is paid to the silicon dioxide film 15 and the insulating layer 13.

As can be seen from FIG. 10B, in the case of the sixth embodiment, the silicon concentration of the insulating layer 13 is
It increases continuously from the two sides to the conductor layer 14 side. Moreover, an amorphous silicon film 16 having a high silicon concentration exists above the insulating layer 13.

Therefore, the current-voltage characteristics change greatly according to the polarity of the voltage application.

FIG. 11 shows a method of manufacturing a semiconductor device according to the sixth embodiment of the present invention in the order of steps.

In FIG. 11, first, an impurity is introduced into a silicon substrate 11 of one conductivity type to form a diffusion layer 12.
Next, a silicon dioxide film 15 is formed on the diffusion layer 12 by LPCVD or thermal oxidation.

Further, on this silicon dioxide film 15, an amorphous silicon film 16 is deposited by LPCVD.

Subsequently, the amorphous silicon film 16
To oxidize. If this oxidation time is appropriately selected, an insulating layer 13 in which a thin non-oxidized amorphous silicon film remains below the silicon dioxide film is formed. That is, the insulating layer 13 has extra silicon in silicon dioxide, and the same effect can be expected.

Thereafter, the conductor layer 1 is placed on the insulating layer 13.
4 is formed.

As described above, according to the sixth embodiment, the insulating layer 13 has a distribution in which the silicon concentration continuously increases toward the diffusion layer 12 side, and the insulating layer 13 has a distribution below the insulating layer 13. Since the silicon dioxide film 15 exists, asymmetric current-voltage characteristics can be realized.

In the above description, the amorphous silicon film 16 is formed on the silicon dioxide film 15 in the manufacturing process shown in FIG. 11, but a polysilicon film may be used instead of the amorphous silicon film 16. Good.

[0106]

According to the present invention, in a semiconductor device having an MIS structure, the silicon concentration of the insulating layer is richer than that of silicon dioxide, and the silicon concentration has a distribution that changes from the semiconductor side to the conductor layer side. By doing so, an excellent semiconductor device which can have asymmetric current-voltage characteristics in both positive and negative polarities can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a semiconductor device according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing the semiconductor device according to the first embodiment of the present invention in the order of manufacturing steps;

FIG. 3 is an explanatory diagram of a semiconductor device according to a second embodiment of the present invention;

FIG. 4 is a cross-sectional view showing a semiconductor device according to a second embodiment of the present invention in the order of manufacturing steps;

FIG. 5 is an explanatory diagram of a semiconductor device according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a semiconductor device in Embodiment 3 of the present invention in the order of manufacturing steps.

FIG. 7 is a cross-sectional view showing a semiconductor device according to a fourth embodiment of the present invention in the order of manufacturing steps;

FIG. 8 is an explanatory diagram of a semiconductor device according to a fifth embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a semiconductor device according to a fifth embodiment of the present invention in the order of manufacturing steps.

FIG. 10 is an explanatory diagram of a semiconductor device according to a sixth embodiment of the present invention.

FIG. 11 is a sectional view showing a semiconductor device in a sixth embodiment of the present invention in the order of manufacturing steps.

FIG. 12 is an explanatory view of a conventional semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Semiconductor substrate 12 Diffusion layer 13 Oxide film 14 Conductive layer 15 Silicon dioxide film 16 Amorphous or polysilicon film

Claims (11)

[Claims] 1. A semiconductor device having a MIS structure including a conductor layer, an insulating layer, and a semiconductor, wherein the insulating layer is formed of a composition having a silicon concentration richer than silicon dioxide, and has a silicon concentration higher than that of silicon dioxide. A semiconductor device having a distribution that changes from the semiconductor side to the conductor layer side. 2. The semiconductor device according to claim 1, wherein the silicon concentration has a distribution that continuously increases or decreases from the semiconductor side to the conductor layer side. 3. The semiconductor device according to claim 1, wherein the silicon concentration has a distribution that increases or decreases stepwise in a plurality of steps from the semiconductor side to the conductor layer side. 4. The semiconductor device according to claim 1, wherein a silicon dioxide film is interposed between said semiconductor and said insulating layer.
The semiconductor device according to claim 3. 5. A step of forming an insulating layer, which is a composition having a silicon concentration richer than that of silicon dioxide, using a laughing gas and a silane-based gas on a semiconductor, and forming a conductive layer on the insulating layer. Forming a semiconductor device. 6. A step of forming a silicon dioxide film on a semiconductor, and using a laughing gas and a silane-based gas on the silicon dioxide film to form an insulating material having a silicon concentration richer than that of silicon dioxide. A method of manufacturing a semiconductor device, comprising: forming a layer; and forming a conductor layer on the insulating layer. 7. The step of forming the insulating layer includes the step of continuously changing the flow rate ratio between the laughing gas and the silane-based gas to continuously change the silicon concentration in the insulating layer from the semiconductor side to the conductor layer side. 7. The method of manufacturing a semiconductor device according to claim 5, wherein the number is increased or decreased. 8. The step of forming the insulating layer comprises changing the silicon concentration in the insulating layer from the semiconductor side to the conductor layer side by changing the flow ratio of the laughing gas and the silane-based gas in a plurality of steps in a time-division manner. 7. The method for manufacturing a semiconductor device according to claim 5, wherein the increase or decrease is performed stepwise. 9. A step of forming a silicon dioxide film on a semiconductor; and a step of ion-implanting silicon into the silicon dioxide film to form an insulating layer having a composition having a silicon concentration richer than that of the silicon dioxide. Forming a conductor layer on the insulating layer. A method for manufacturing a semiconductor device, comprising: 10. A step of forming a silicon dioxide film on a semiconductor, a step of forming an amorphous silicon or polysilicon film on the silicon dioxide film, and a step of forming silicon dioxide through the amorphous silicon or polysilicon film. Forming a dielectric layer of a composition having a silicon concentration richer than that of the silicon dioxide film by ion-implanting silicon into the film. 11. A step of forming a silicon dioxide film on a semiconductor, a step of forming an amorphous silicon or polysilicon film on the silicon dioxide film, and oxidizing the amorphous silicon or polysilicon film to form a silicon dioxide film. Forming an insulating layer that is a composition having a silicon concentration richer than that of silicon.