JPH10233504A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the diffusion of a dopant into a gate insulating film from a gate electrode by making the gate insulating film contain an insulating film formed by heavily doping a silicon film with nitrogen. SOLUTION: After a silicon oxide film and an amorphous silicon film are successively formed on a silicon substrate 1, the amorphous silicon film is entirely transformed into a silicon oxynitride film by heating the film in a nitrogen monoxide atmosphere and a polycrystalline silicon film is formed on the silicon oxynitride film. Then a three-layer film having an ONO (silicon oxide film/ silicon nitride film/silicon oxide film) structure is formed by successively forming a silicon oxide film, a silicon nitride film, and a silicon oxide film on the silicon oxynitride film and a polycrystalline silicon film is formed on the three-layer film. Thereafter, a control gate electrode 7 composed of the polycrystalline silicon film, an interlayer insulating film 6 composed of the three-layer film, a floating gate electrode 5 composed of the polycrystalline silicon film, and a gate insulating film 4 composed of the silicon oxynitride film are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having stable operation characteristics and high reliability, and a semiconductor device capable of easily manufacturing such a semiconductor device. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In a conventional nonvolatile semiconductor memory device having a gate portion having a laminated structure shown in FIG. 1, for example, a voltage of +4 V is applied to a drain 9 and a voltage of -10 V is applied to a control gate electrode 7 and a source 8 Is released and the substrate 1 is grounded, so that electrons accumulated in the floating gate electrode 5 are drawn out to the drain 9 side, and information is written.
In this semiconductor memory device, Fowler-Nordhe
By the im tunnel current (FN current), electrons in the floating gate electrode 5 are extracted to the drain 9 side via the gate insulating film 4, and holes are simultaneously injected from the drain 9 side into the gate insulating film 4. However, when writing and erasing are repeatedly performed, the injected holes are generated in the gate insulating film 4.
In particular, it is trapped in the vicinity of the interface between the gate insulating film 4 and the substrate 1 and causes characteristic deterioration.

[0003] In order to suppress such characteristic deterioration, for example, the related art 1: Extended Abstract.
Of the 22nd Conference on Solid State Devices and Materials (EXT
ENDED ABSTRACT OF THE 22N
D CONFERENCE ON SOLID STA
TE DEVICES AND MATERIALS)
As shown in page 1155 (1990), a silicon oxynitride film is formed at the interface between a silicon dioxide film, which is a gate insulating film, and a silicon substrate using nitrous oxide. Have been proposed. When nitrogen is introduced into the interface between the gate insulating film and the silicon substrate by using this method, a trap level in the gate insulating film is reduced, and an increase in a writing time caused by repeating rewriting can be suppressed.

At the interface between the polycrystalline silicon film (gate electrode) and the silicon oxide film (gate insulating film), there are irregularities on the nanometer level. Phosphorus concentration, contained as
The temperature can be reduced by lowering the heat treatment temperature after the introduction of phosphorus, and the silicon nitride film formed by the reduced pressure chemical vapor deposition method using dichlorosilane and ammonia can be combined with a polycrystalline silicon film and an oxide film. By inserting between the silicon film and the silicon film, the reaction between the two can be suppressed. As described above, when nitrogen is present at the interface between the gate electrode and the gate insulating film, diffusion of the dopant added to the gate electrode into the silicon substrate is suppressed, and the threshold value is stabilized. This is particularly noticeable when boron is used as an electrode dopant (Prior Art 2: Extended Abstract.
Of the 22nd Conference on Solid State Devices and Materials (EXT
ENDED ABSTRACT OF THE 22N
D CONFERENCE ON SOLID STA
TE DEVICES AND MATERIALS)
267 (1990)).

[0005]

The effect of stabilizing the threshold value described in the above prior art 1 is achieved by heat-treating the gate insulating film made of silicon oxide in nitrous oxide so that the gate insulating film and the silicon substrate are not heat-treated. A silicon oxynitride film is formed at the interface between the silicon oxide films and the nitrogen contained in the silicon oxynitride film suppresses the diffusion of the dopant into the silicon substrate.

However, in the method described in the prior art 1, although the diffusion of the dopant into the silicon substrate can be prevented, the diffusion of the dopant into the gate insulating film cannot be prevented, and the reliability of the gate insulating film decreases. Resulting in. Therefore, in order to increase the reliability of the gate insulating film, it is necessary to prevent the diffusion of the dopant at the interface between the gate electrode and the gate insulating film and to prevent the dopant from diffusing into the gate insulating film.

Further, as described in the prior art 2, when a silicon nitride film is formed by a low pressure chemical vapor deposition method using dichlorosilane and ammonia, hydrogen is taken into the silicon nitride film at the time of formation, An N—H bond or the like becomes an electron trap level. Therefore, in order to prevent the diffusion of the dopant by the silicon nitride film formed by this method and to improve the reliability of the MOS semiconductor device, it is necessary to reduce the number of electron trap levels by thinning the silicon nitride film. Not be. However, it is extremely difficult to form a thin silicon nitride film having a uniform thickness by the low pressure chemical vapor deposition method, and the dopant passes through the thin portion and diffuses into the gate insulating film. .

[0008] Such a problem occurs not only in a non-volatile semiconductor device but also in a MOS transistor or a capacitor having a MOS structure. Diffusion of a dopant from a gate electrode can be effectively prevented. High and thin insulating films have been strongly desired.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, to prevent diffusion of a dopant from a gate electrode into a gate insulating film, to have a small number of electron capture levels, and to have a uniform film thickness. It is an object of the present invention to provide a semiconductor device having a simple gate insulating film and a method for manufacturing the same.

[0010]

According to the present invention, there is provided a semiconductor device having a gate electrode provided on a main surface of a semiconductor substrate having a first conductivity type via a gate insulating film. In the semiconductor device described above, the gate insulating film includes an insulating film formed by doping a silicon film with a large amount of nitrogen.

That is, although silicon is a semiconductor, if it is doped with a large amount of nitrogen, it exhibits characteristics not as a semiconductor but as an insulator. In the semiconductor device of the present invention, a silicon film doped with a large amount of nitrogen to form an insulator is used as a gate insulating film.

An ordinary silicon nitride film is formed by a method such as CVD utilizing a gas phase reaction. In the silicon nitride film formed by such a method, as described above, the film forming process is performed. , Hydrogen is taken into the film. However, a silicon film is formed in advance,
If a large amount of nitrogen is doped into the silicon film to form an insulator, hydrogen is hardly taken into the film, and the number of electron trap levels can be effectively suppressed. Instead of forming the silicon film in advance, the exposed surface of the silicon substrate and a large amount of nitrogen may be doped.

Therefore, if a gate insulating film is formed by doping a large amount of nitrogen into a silicon film by such a method and a gate electrode is formed thereon, the diffusion of the dopant from the gate electrode to the gate insulating film can be prevented. This is effectively prevented, the reliability of the gate insulating film is improved, and the threshold level of the electrons does not fluctuate since the number of trapped electrons does not increase.

When the silicon film doped with a large amount of nitrogen is further doped with a large amount of oxygen together with the nitrogen, a more excellent effect can be obtained than when only the nitrogen is doped.

The above gate insulating film can be used as a gate insulating film of a nonvolatile semiconductor memory device having a stack structure. Therefore, the gate electrode in this case is a floating gate electrode of the nonvolatile semiconductor memory device, and an interlayer insulating film and a control gate electrode are formed on the floating gate electrode.

Further, the gate insulating film can be used as a gate insulating film of a MOS transistor. Therefore, in this case, the gate electrode is a gate electrode of a MOS transistor.

Further, the gate electrode can be used as a capacitor insulating film of a MOS type capacitor,
In this case, the gate electrode is a plate electrode of the capacitor. The capacitor insulating film can be formed not only on a silicon substrate but also on a polycrystalline silicon film extending over an element isolation insulating film or a gate electrode to form a structure generally called a multilayer capacitor.

The gate insulating film may be composed of a laminated film of two or more layers. In this case, the silicon film doped with a large amount of nitrogen is disposed as an upper layer so as to be in contact with the gate electrode. Is preferred. The same applies to the case where a large amount of oxygen is doped in the silicon film in addition to nitrogen. As the lower layer film in contact with the silicon substrate, a silicon oxide film is preferable.

For the gate electrode, a low-resistance polycrystalline silicon film containing a high-concentration dopant can be used.
Diffusion of the dopant from the gate electrode is effectively prevented by the gate insulating film.

In the semiconductor device of the present invention, a step of forming a silicon film on a predetermined region of the main surface of the semiconductor substrate and a heat treatment in a gas containing nitrogen radicals, nitric oxide or nitrous oxide are performed. The method can include a step of forming a gate insulating film by doping a large amount of nitrogen into the silicon film and a step of forming a gate electrode on the gate insulating film. When nitrogen radicals are used, a silicon nitride film is formed,
When heat treatment is performed in a gas containing nitric oxide or nitrous oxide, a silicon oxynitride film is formed.

That is, the gate insulating film is formed by ordinary CVD.
Instead, the silicon film is formed by performing a heat treatment in a gas containing nitrogen radicals, nitric oxide or nitrous oxide, and doping a large amount of nitrogen into the silicon film. Therefore, the formed gate insulating film does not contain hydrogen and contains a large amount of nitrogen, which not only prevents the diffusion of the dopant from the gate electrode, but also reduces the trap level, and A thin gate insulating film having a uniform thickness is formed. When a nitrogen radical is used, a silicon nitride film is formed.
₃ film having a composition close to the N ₄ can be obtained. Similarly, when nitrous oxide and nitric oxide are used, if the treatment is sufficiently performed,
A silicon oxynitride film containing a large amount of nitrogen is obtained.

Since the depth of nitrogen doped into the silicon film by one heat treatment is not large, if the silicon film formation and the heat treatment are performed only once, a predetermined film thickness (for example, 8 nm) is obtained. This is practically difficult, and it is preferable to form a gate insulating film having a predetermined thickness by repeating the formation of a thin silicon film and the heat treatment a plurality of times.

As the silicon film, an amorphous silicon film formed by a known chemical vapor deposition method can be used. As a result, the film thickness at the nanometer level can be controlled with high accuracy, and the uniformity of the film thickness is excellent.

After a silicon oxide film is formed on a predetermined region of the silicon substrate, the silicon film may be formed on the silicon oxide film and heat-treated to form a two-layer film. The silicon oxide film may be formed by oxidizing the exposed surface of the silicon substrate, or may be formed by forming a silicon film on the silicon substrate and oxidizing the silicon film.

Further, the exposed surface of the silicon substrate is heat-treated in a gas containing nitrogen radicals, nitric oxide or nitrous oxide to dope the exposed surface of the silicon substrate with a large amount of nitrogen to form a gate insulating film. After forming the film,
A gate electrode may be formed on this gate insulating film. In this case, a gate electrode is formed over a gate insulating film including only a silicon nitride film or a silicon oxynitride film without the silicon oxide film.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a semiconductor device according to the present invention,
On the surface of the silicon substrate, a gate insulating film including an insulating film made of a silicon film doped with a large amount of nitrogen to form an insulator is formed, and a gate electrode is disposed thereon.

When a silicon film is doped with a large amount of nitrogen, the film becomes an insulating film. However, to dope a large amount of nitrogen into the silicon film, a nitrogen radical, nitric oxide or nitrous oxide is contained in a gas containing gas. What is necessary is just to heat-treat a silicon film. When heat treatment is performed in an atmosphere containing nitrogen radicals, a silicon nitride film is formed. When heat treatment is performed in a gas containing nitric oxide or nitrous oxide, a silicon oxynitride film is formed.

As the atmosphere gas for the heat treatment, a gas containing 1% to 100% of nitrogen radicals, a gas containing 0.5% to 100% of nitric oxide, and 1% of nitrous oxide are used, respectively.
A gas containing 0% to 100% can be used. The temperature of the heat treatment is 400 ° C. to 8 when nitrogen radicals are used.
00 ° C., 600 ° C. to 950 when nitric oxide is used
° C, and when nitrous oxide is used, a preferred result is obtained if the temperature is set to 800 ° C to 1000 ° C.

The silicon film is preferably an amorphous silicon film formed by a low-pressure chemical vapor deposition method, and can control a thin film thickness of nanometer level with high accuracy. Also, instead of forming a silicon film, an insulating film made of silicon doped with a large amount of nitrogen can be formed by exposing a desired region of a silicon substrate and performing the above heat treatment.

The gate insulating film is not limited to a nonvolatile semiconductor memory device, but may be a MOS transistor or a MOS transistor.
In either case, the diffusion of the dopant into the gate insulating film can be effectively prevented.

[0031]

【Example】

<Embodiment 1> A first embodiment of the present invention will be described with reference to FIG. First, a thick insulating film 2 for element isolation is formed on the surface of a silicon substrate 1 by using a well-known thermal oxidation method, and then oxygen and hydrogen are flowed simultaneously, and a 6-nm-thick silicon oxide film is formed by well-known pyrogenic oxidation. To the above silicon substrate 1
Formed on top. The flow rates of the oxygen and hydrogen are each 1
0 liter / min and 0.5 liter / min, temperature 85
0 ° C.

A nitrogen gas having a gas pressure of 73 Pa and a flow rate of 2 L / min is used as a carrier gas, and disilane is used at a flow rate of 0.
At a flow rate of 15 liters / minute, an amorphous silicon film having a thickness of 0.5 nm was formed on the silicon oxide film. The temperature at this time was 425 ° C. Next, the amorphous silicon film was heated to 850 ° C. in nitrogen monoxide to entirely form a silicon oxynitride film. The process of forming the amorphous silicon film and the oxynitriding process were repeated seven times to increase the film thickness, thereby forming a silicon oxynitride film having a predetermined film thickness (8 nm).

By a well-known reduced pressure chemical vapor deposition method using monosilane and phosphine as a source gas, a concentration of 3 ×
A 200-nm-thick polycrystalline silicon film containing 10 ²⁰ cm ⁻³ of phosphorus was formed on the silicon oxynitride film 4 by lamination.

Next, a 6-nm-thick silicon oxide film is formed on the silicon oxynitride film by a well-known low-pressure chemical vapor deposition method using nitrous oxide and monosilane, and ammonia and dichlorosilane are used. An 8 nm-thick silicon nitride film was formed on the silicon oxide film by a known low pressure chemical vapor deposition method. Subsequently, by a well-known reduced pressure chemical vapor deposition method using nitrous oxide and monosilane,
A silicon oxide film having a thickness of 4 nm was formed on the silicon nitride film to form a three-layer film having an ONO (silicon oxide film-silicon nitride film-silicon oxide film) structure.

On the interlayer insulating film, a well-known low pressure chemical vapor deposition method using monosilane and phosphine as a source gas is used to form a layer containing phosphorus having a concentration of 3 × 10 ²⁰ cm ^-3.
A polycrystalline silicon film of 00 nm was formed on the three-layer film.

Unnecessary portions of the polycrystalline silicon film, the three-layer film, the polycrystalline silicon film, and the silicon oxynitride film are sequentially removed from above using a well-known photo-etching using a mask. , An interlayer insulating film 6 made of the three-layer film, a floating gate electrode 5 made of the polycrystalline silicon film, and a gate insulating film 4 made of the silicon oxynitride film.

After the side wall silicon oxide film 11 is formed on the side portions of the floating gate electrode 5 and the control gate electrode 7 by performing thermal oxidation, a well-known ion implantation is performed to perform the opposite ion implantation to the silicon substrate 1. A source 8 and a drain 9 having a conductivity type were formed, and further, an insulating film 10 and a source / drain electrode 3 were formed by using a well-known method, whereby the memory cell for a nonvolatile semiconductor memory device shown in FIG. 1 was manufactured. .

The rewriting characteristics of the obtained nonvolatile semiconductor memory device were evaluated as follows. That is, charge injection (erase) into the floating gate electrode 5 using the entire surface of the control gate electrode 7 was performed by the FN current, and the charge was extracted from the floating gate electrode 5 to the drain 9 by the FN current to perform a write operation. . The potential at the time of erasing was +12 V for the control gate electrode 7, and 0 V for the source 8, the drain 9 and the substrate 1. The potential at the time of writing was such that the control gate electrode 7 was -10 V, the drain 9 was +4 V, the source was open, and the substrate 1 was grounded.

Under such conditions, the conventional nonvolatile semiconductor memory device using the nonvolatile semiconductor memory device obtained by this embodiment and the silicon oxide film having a thickness of 8 nm formed by pyrogenic oxidation as the gate insulating film 4 is used. As a result of measuring the writing characteristics of the device, the results shown in FIG. 4 were obtained. As is clear from FIG. 4, the ratio Tpw of the writing time Tpw after rewriting to the initial writing time Tpwi.
/ Tpwi increases as the number of rewrites increases,
This increase could be suppressed to less than half of the prior art by this embodiment.

Further, the drain 9 is set to +5 V, the control gate electrode 7, the source 8 and the silicon substrate 1 are set to 0 V, and 10
Keeping seconds to measure charge retention characteristics after rewriting 10 ⁴ times. When the threshold distribution after the voltage stress was examined, in the case of the above-mentioned conventional technique, 30 bits out of 16 Mbits had a large variation in threshold value and became defective. It was only 2 bits and could be significantly reduced.

In this embodiment, the amorphous silicon film for forming the silicon oxynitride film is formed by using disilane. The same effect was obtained by using the raw material gas.

<Embodiment 2> A second embodiment of the present invention will be described with reference to FIG. After a thick insulating film 32 for element isolation is formed on the surface of the silicon substrate 31 using a well-known thermal oxidation method, the exposed surface of the silicon substrate 31 is oxynitrided by heating to 900 ° C. in nitrogen monoxide. Then, a silicon oxynitride film having a thickness of 2 nm was formed on the silicon substrate 31.

On this silicon oxynitride film, a gas pressure of 73 P
a, Disilane was flowed at a flow rate of 0.15 L / min using a nitrogen gas as a carrier gas at a flow rate of 2 L / min to form an amorphous silicon film having a thickness of 0.5 nm. The formation temperature at this time was 425 ° C.

The amorphous silicon film was heated to 900 ° C. in nitrogen monoxide to form a silicon oxynitride film. The formation of the amorphous silicon film and the oxynitridation process were repeated three times to form a gate insulating film 34 having a predetermined thickness (4 nm).

Next, a well-known reduced pressure chemical vapor deposition method using monosilane as a source gas is used to form a film having a thickness of 200 nm.
After forming the polycrystalline silicon film, the implantation energy 2
Under the conditions of 5 keV and a dose of 6 × 10 ¹⁵ cm ⁻² , boron (BF ₂ ) is ion-implanted into the polycrystalline silicon film, and annealed at 900 ° C. in nitrogen gas.
Unnecessary portions were removed using a well-known photo-etching using a mask to form a gate electrode 35 having a predetermined shape.

After thermal oxidation is performed to form a side wall silicon oxide film 41 on the side of the gate electrode 35 and the like, the source 36 and the drain 37 are formed by well-known ion implantation.
Then, the insulating film 38, the source 36, and the drain electrode 33 were formed by using a well-known method, and the MOS transistor shown in FIG. 2 was manufactured.

The dependence of the initial threshold voltage of the obtained MOS transistor on the nitrogen annealing time was examined, and the conventional MOS transistor using a pyrogenic oxide film as the gate insulating film 34 was examined.
Compared to transistors. As a result, as shown in FIG. 5, in the case of the above-described conventional MOS transistor, when the annealing time is long, the threshold voltage is significantly increased due to the diffusion of boron from the gate electrode. Since the diffusion of boron from 35 is prevented by the gate insulating film 34 made of the silicon oxynitride film, the threshold voltage did not change even if the annealing time was long.

Next, (gate voltage−threshold voltage) = −
1 V and a drain voltage of -8 V were applied, and the variation of the threshold voltage from the initial stage was examined. As a result, as shown in FIG. 6, in the above-described conventional MOS transistor, the threshold voltage fluctuation increases as the time during which the stress is applied becomes longer. Hardly changed, and extremely stable characteristics were obtained.

<Embodiment 3> A third embodiment of the present invention will be described with reference to FIG. After a thick insulating film 22 for element isolation is formed on the surface of the silicon substrate 21 by using a well-known thermal oxidation method, oxygen and hydrogen are simultaneously caused to flow, and a 7.5-nm-thick silicon oxide film is formed by well-known pyrogenic oxidation. Was formed on the silicon substrate 21. The oxygen and hydrogen flow rates were 10 liters / minute and 0.5 liters / minute, respectively.
Minutes and the temperature was 850 ° C.

On this silicon oxide film, a gas pressure of 73 P
a, Using a nitrogen gas as a carrier gas at a flow rate of 2 L / min, disilane was flowed at a flow rate of 0.15 L / min to form an amorphous silicon film having a thickness of 1 nm at 425 ° C. Next, the amorphous silicon film was heated to 900 ° C. in nitrous oxide to form a silicon oxynitride film. The formation of the amorphous silicon film and the oxynitridation process were repeated six times to form the gate insulating film 23 having a predetermined thickness (9 nm). On this gate insulating film 23,
The concentration is 3 × 10 ²⁰ cm by a well-known reduced pressure chemical vapor deposition method using monosilane and phosphine as a source gas.
After forming a 200-nm-thick polycrystalline silicon film containing phosphorus of ^-3 , unnecessary portions are removed using a well-known photo-etching using a mask, and a gate electrode 24 is formed.
A MOS capacitor having the cross-sectional structure shown in FIG.

The gate electrode 2 of the obtained MOS capacitor
4. High electric field stress (100 mA / cm at negative gate voltage)
² was applied for 100 seconds) and the fluctuation of the flat band voltage before and after the application of the stress was examined. on the other hand,
For a conventional MOS capacitor using a silicon oxide film having a thickness of 9 nm formed by pyrogenic oxidation as the gate insulating film 23, the variation of the flat band voltage was examined in the same manner, and the two were compared. FIG. 7 shows the obtained results.

As is apparent from FIG. 7, in the capacitor formed according to this embodiment, the fluctuation of the flat band voltage due to the stress was much smaller than that of the conventional capacitor.

Further, since the capacitor obtained in this embodiment can reduce the charge trapping, the fluctuation of the gate electric field when the constant current stress is applied (at a gate negative voltage of 10 mA / cm ² ) is also shown in FIG. As shown, the stability of the characteristics of the present invention was improved by far less than that of the conventional capacitor.

In this embodiment, the capacitor using the silicon substrate 21 as the lower electrode is shown. However, not only the silicon substrate but also a stacked type using the polycrystalline silicon film formed on the silicon substrate as the lower electrode. Needless to say, the present invention can be applied to a capacitor.

[0055]

As is apparent from the above description, according to the present invention, the diffusion of the dopant from the gate electrode made of the polycrystalline silicon film is extremely effectively prevented,
Since the number of trap levels in the gate insulating film is small, deterioration of the gate insulating film due to rewriting can be prevented, the charge retention characteristics of the nonvolatile semiconductor memory device can be significantly improved, and the increase in write time can be suppressed.

Further, a MOS transistor having a stable threshold value and a high hot carrier resistance can be obtained.
The fluctuation of the flat band voltage and the fluctuation of the gate voltage of the S capacitor can be extremely reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a nonvolatile semiconductor device according to a first embodiment of the present invention;

FIG. 2 is a sectional view of a MOS transistor showing a second embodiment of the present invention;

FIG. 3 is a sectional view of a MOS capacitor according to a third embodiment of the present invention;

FIG. 4 is a diagram for explaining the effect of the first embodiment of the present invention;

FIG. 5 is a diagram for explaining the effect of the second embodiment of the present invention;

FIG. 6 is a diagram for explaining the effect of the second embodiment of the present invention;

FIG. 7 is a diagram for explaining the effect of the third embodiment of the present invention;

FIG. 8 is a diagram for explaining the effect of the third embodiment of the present invention.

[Explanation of symbols]

1, 21: silicon substrate, 2, 22, 32: element isolation insulating film, 3: electrode, 4, 23: gate insulating film, 5: floating gate electrode, 6: interlayer insulating film, 7: control gate electrode, 8 ...
Source: 9, drain: 10: insulating film, 11: sidewall silicon oxide film, 24: gate electrode, 31: Si substrate, 33
... Electrode, 34 ... Gate insulating film, 35 ... Gate electrode, 36
... source, 37 ... drain, 38 ... insulating film, 41 ... side wall silicon oxide film.

Claims (14)

[Claims] In a semiconductor device having a gate electrode provided on a main surface of a semiconductor substrate having a first conductivity type with a gate insulating film interposed therebetween, the gate insulating film is doped with a large amount of nitrogen. A semiconductor device comprising a silicon film. 2. The semiconductor device according to claim 1, wherein said silicon film is further doped with a large amount of oxygen. 3. The method according to claim 1, wherein the gate electrode is a floating gate electrode of a nonvolatile semiconductor memory device, and an interlayer insulating film and a control gate electrode are formed on the floating gate electrode. The semiconductor device according to claim 1. 4. The semiconductor device according to claim 1, wherein said gate electrode is a gate electrode of a MOS transistor. 5. The semiconductor device according to claim 1, wherein said gate electrode is a plate electrode of a capacitor. 6. The semiconductor device according to claim 1, wherein said gate insulating film comprises a laminated film of two or more layers. 7. The semiconductor device according to claim 1, wherein said silicon film doped with a large amount of nitrogen is in contact with said gate electrode. 8. The semiconductor device according to claim 1, wherein said gate electrode is made of a low-resistance polycrystalline silicon film containing a high-concentration dopant. 9. A process for forming a silicon film on a predetermined region on a main surface of a semiconductor substrate, and performing a heat treatment in a gas containing nitrogen radicals, nitric oxide or nitrous oxide to remove a large amount of nitrogen from the silicon film. A method for manufacturing a semiconductor device, comprising: a step of forming a gate insulating film by doping; and a step of forming a gate electrode on the gate insulating film. 10. The method according to claim 9, wherein the gate insulating film is formed by performing the formation of the silicon film and the heat treatment a plurality of times. 11. The method for manufacturing a semiconductor device according to claim 9, wherein said silicon film is an amorphous silicon film formed by a chemical vapor deposition method. 12. The semiconductor device according to claim 9, wherein said silicon film is formed on said silicon oxide film after forming said silicon oxide film on said predetermined region. Device manufacturing method. 13. The semiconductor device according to claim 12, wherein the silicon oxide film is formed by oxidizing an exposed surface of a silicon substrate or a silicon film formed on the silicon substrate. Production method. 14. A step of heat-treating a silicon substrate in a gas containing nitrogen radicals, nitric oxide or nitrous oxide to dope a large amount of nitrogen into an exposed surface of the silicon substrate to form a gate insulating film. And a step of forming a gate electrode on the gate insulating film.