JP2001237242A - Semiconductor device and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device for recovering damage of an oxide film at an edge of a thin film deposited partly on the oxide film. SOLUTION: In order to restore damage in the oxide film, a heat treatment is carried out after the process that causes the damage. While the surface of the oxide film is exposed as much as possible, the heat treatment is carried out under atmosphere of an inert gas like nitrogen gas, hydrogen gas, argon gas, the mixture or mixture containing several percentages of oxygen at not less than 800 deg.C, preferably at 950 deg.C or above for not less than 5 minutes, preferably 20 minutes or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device and a semiconductor device, and more particularly to a highly integrated semiconductor device.
The present invention relates to a method for manufacturing a semiconductor device suitable for forming a thermal oxide film and a semiconductor device obtained by the method.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices using silicon as a substrate, a silicon oxide film formed by thermally oxidizing silicon is used as an insulating film. In the process of forming the thermal oxide film, a large strain (stress) is generated in the vicinity of the interface between the silicon and the oxide film because the silicon-silicon bond is broken and the silicon-oxygen bond is formed.

The molecular volume of silicon oxide is two times that of silicon.
Since it is twice or more, the oxide film formed by the oxidation reaction tends to expand, so that a tensile stress is generally generated on the silicon side and a compressive stress is generated on the oxide film side. When the generated stress increases, crystal defects such as dislocations are generated in the single crystal silicon substrate. The presence of the crystal defects causes a leakage current or the like in a semiconductor element, and thus significantly lowers the reliability of a product.

[0004] Even if no crystal defects occur in the silicon substrate, the stress generated in the oxide film causes a distortion in the interatomic distance in the oxide film, and the bonding force between atoms is reduced. In some cases, damage such as breaking of atomic bonds may occur. When such damage occurs, the insulating properties of the oxide film are reduced, and the electrical reliability of the oxide film and, consequently, the reliability of the product are reduced.

Generally, the value of the generated stress monotonically increases as the thickness of the oxide film to be formed increases. Therefore, when a thick thermal oxide film is formed, relaxation of the generated stress is an important issue. As a method of relaxing the stress, Japanese Patent Laid-Open No.
As described in US Pat. No. 1,733, a method has been proposed in which thermal oxidation is interrupted halfway, heat treatment for strain relief is performed, and then thermal oxidation is continued again.

[0006]

The mechanism by which the stress is generated in the oxide film mainly includes the stress caused by the volume expansion of the oxide film near the silicon / oxide film interface based on the oxidation reaction in the oxide film formation process, and the oxidation. There is stress generated from the thin film deposited on the film.

[0007] Although stress relaxation caused by an oxidation reaction was possible to some extent in the prior art, there was no effective stress relaxation method for stress generated from a thin film deposited on an oxide film. The stress generated from the thin film deposited on the oxide film is generated by the following mechanism.

First, as an oxide film forming process, an oxide film for element isolation is partially formed with a thickness of about several thousand angstroms in order to electrically insulate and isolate, for example, transistors adjacent to the surface of a silicon substrate. There is a process for forming As a method for forming the element isolation oxide film, a selective oxidation method is widely used (see FIG. 2).
In this selective oxidation method, a silicon nitride film 3 is deposited on a silicon substrate 1 (FIG. 2A) via, for example, a thin thermal oxide film called a pad oxide film 2 (FIG. 2B) (FIG. 2B).
(C)) The silicon nitride film 3 in the region where the element isolation oxide film is to be formed is removed by etching (FIG. 2 (d)), and the whole is oxidized to form a thick oxide film partially on the silicon substrate. This is a method of forming (FIG. 2E).

The silicon nitride film used as the oxide protective film in this selective oxidation method has a thickness of 1000 M at the time of film deposition.
It often has an internal stress of about Pa, and this stress also acts on the oxide film. Furthermore, in the selective oxidation process, oxygen or H2O, which is an oxidizing species, diffuses three-dimensionally in the silicon substrate, so that an oxide film 5 called a bird's beak grows near the end of the silicon nitride film.

During the growth of the oxide film, the volume of the oxide film expands, so that the silicon nitride film at the end of the silicon nitride film is lifted, and the entire film is warped. Since the reaction force generated due to the warp deformation is concentrated on the silicon nitride film edge, a large stress is generated in the oxide film at the silicon nitride film edge. Therefore, in the state where the silicon nitride film exists, the stress concentration always occurs, and the oxide film is damaged.

As another process in which a thin film deposited on an oxide film causes damage to the oxide film, there is a process of depositing a thin film as a gate electrode on a gate oxide film of a MOS (Metal-Oxide-Semiconductor) transistor. . As the gate electrode, a polycrystalline silicon thin film, a high melting point metal material, a silicide alloy thin film, or the like is used in a single-layer or multilayer structure.

[0012] Such a gate electrode material still has several hundred to
It is often deposited with an internal stress exceeding 1,000 MPa. Therefore, when the gate electrode is processed, stress concentration occurs in the oxide film near the end of the gate electrode due to the internal stress, and the oxide film is damaged.

An object of the present invention is to provide a method of manufacturing a semiconductor device for recovering damage of an oxide film at an end of a thin film partially deposited on the oxide film, and a semiconductor device obtained by the method.

[0014]

In order to recover damage in the oxide film, the surface of the oxide film is exposed as much as possible after the damaged process at a temperature of at least 800 ° C. for at least 5 minutes. As described above, it is effective to perform the heat treatment for at least 20 minutes if possible. In the process of forming an oxide film for element isolation by the selective oxidation method, after the selective oxidation is completed, for example, a silicon nitride film or a polycrystalline silicon thin film used as an oxide protective film is entirely removed, and the oxide film or the silicon substrate surface is exposed. In the state, heat treatment is performed at a temperature of 800 ° C. or more, more preferably 950 ° C. or more, for at least 5 minutes or more, and preferably 30 minutes or more. After the heat treatment after the formation of the element isolation oxide film, the MO
Even after forming the gate oxide film of the S-type transistor, heat treatment is performed at a temperature of 800 ° C. or more for at least 5 minutes or more, preferably 30 minutes or more with the oxide film surface exposed. Further, even after the gate electrode is formed (patterned) on the gate oxide film, heat treatment is performed at a temperature of 800 ° C. or more for at least 5 minutes or more, preferably 20 minutes or more with the gate electrode and the oxide film exposed.

Therefore, the method of manufacturing a semiconductor device according to the present invention is characterized by any one of the following aspects, and the semiconductor device according to the present invention is manufactured by any one of these methods. .

(1): After forming the thermal oxide film, at least 8% with the oxide film or the silicon substrate surface exposed.
Heat treatment is performed at a temperature of 00 ° C. or more for 5 minutes or more.

(2): forming a partially thick oxide film on the surface of the silicon substrate for electrically insulating and separating the semiconductor elements from each other;
In a state where the oxide film or the silicon substrate is exposed, heat treatment is performed at a temperature of at least 950 ° C. for 5 minutes or more.

(3): After forming a partially thick oxide film on the surface of the silicon substrate to electrically insulate and separate the semiconductor elements, a gate oxide film of a MOS transistor is formed, and immediately after the completion of the gate oxidation. Alternatively, heat treatment is performed at a temperature of at least 800 ° C. for at least 5 minutes after the formation of the gate electrode.

(4) In (1), (2) or (3), the semiconductor device is a flash memory, a DRAM, an SR
It is a memory device or an arithmetic device such as an AM.

(5) In any one of the above, the thermal oxidation is at least oxygen, a mixed gas of hydrogen and oxygen, or H
Performed in a 2O atmosphere.

(6) In any one of the above, the atmosphere for the heat treatment is an inert gas such as nitrogen, hydrogen, or argon, or a mixed gas thereof, or a mixed gas containing about several percent of oxygen.

[0022]

When forming an oxide film on a silicon substrate by a thermal oxidation method, the stress generated in the oxide film or the stress generated on the silicon substrate surface (interface with the oxide film) changes depending on the oxidation temperature. This is because there is a stress relaxation mechanism based on the viscoelastic behavior of the thermal oxide film.

FIG. 3 shows an example in which the stress generated in the silicon substrate in the thermal oxidation process is measured by the micro-Raman method. The horizontal axis in the figure is the oxidation temperature, and the vertical axis is the vertical stress parallel to the substrate surface remaining on the silicon substrate surface (interface with the oxide film) at room temperature. The figure collectively shows the measurement results when a mixed atmosphere of hydrogen and oxygen is used as the oxidizing atmosphere and when dry oxygen is used. still,
Oxidation uses a silicon single crystal ((100) plane wafer) and forms an oxide film with a uniform thickness of 50 nm on the silicon surface.

It can be seen that the silicon substrate residual stress monotonously decreases as the oxidation temperature increases. In particular, when a mixed gas of oxygen and hydrogen is used as the oxidizing atmosphere, the stress is remarkably reduced, and decreases to almost zero at 950 ° C. or higher. Such stress relaxation behavior occurs not only in the progress of the oxidation reaction but also when heat treatment is performed after the oxidation reaction is completed.

That is, for example, when a mixed gas of oxygen and hydrogen is used as an oxidizing atmosphere, the oxide film stress is reduced to almost zero even if a heat treatment is added at 950 ° C. for 30 minutes after forming the oxide film at 850 ° C. Decrease. Although the effect of the stress relaxation in the heat treatment process is effective even for about 5 minutes, it is preferable to perform the heat treatment for 20 minutes or more if possible in order to sufficiently relax the stress.

FIG. 3 shows the measurement results when the oxide film thickness is set to 50 nm. When the oxide film thickness is about 100 nm or more, even if it is oxidized at 950.degree. Does not necessarily decrease to zero. This is because it takes time to relax the stress. Therefore, performing the above-described heat treatment after forming the oxide film by the thermal oxidation method is effective in relaxing the stress in the oxide film.

Further, when oxidation is performed using an oxidation protection (prevention) film such as a silicon nitride film as in a selective oxidation method,
As described above, since stress concentration occurs in the oxide film at the end of the oxidation protection (prevention) film, the thin film (in this case, the silicon nitride film) causing the stress is removed after the oxidation is completed.
When heat treatment is added while the surface of the oxide film or the surface of the silicon substrate is entirely exposed, the stress generated due to the presence of the thin film can be reduced together with the oxidation-induced stress.

Further, a gate oxide film of a MOS transistor is often formed at about 850 ° C., and after the film is formed, a large stress often remains in the oxide film. Very effective for stress relaxation.

Also, when a gate electrode is deposited (+ etched) on this gate oxide film, stress concentration occurs in the oxide film at the end of the gate electrode. By adding heat treatment, the stress generated in the oxide film can be reduced.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 1 is a schematic view showing a change in the cross section of a silicon substrate in a process of forming an oxide film for element isolation using the method of manufacturing a semiconductor device according to the present invention. FIG. FIG. 4 is a flow chart showing the manufacturing method of the present embodiment.

First, according to the flowchart of FIG.
This embodiment will be described with reference to FIG. In the present embodiment, the present invention is applied to a selective oxidation process for forming a thick element isolation oxide film in a semiconductor device manufacturing process.

A thin pad oxide film 2 having a thickness of about 10 nm is formed on a silicon substrate 1 (FIG. 1A) by using a thermal oxidation method.
Is formed (FIG. 1B). Oxidation protection (prevention) on this
A silicon nitride film 3 is deposited as a film (FIG. 1C). The silicon nitride film 3 in a region where an element isolation oxide film is to be formed is removed by etching to form an opening, and thermal oxidation (FIG. 4-106)
Is performed to form an element isolation oxide film 4 having a thickness of about several hundred nm (FIG. 1E). Thereafter, the silicon nitride film 3 is entirely removed, and the oxide film 2 or 3 or the silicon substrate 1 is exposed on the surface, and at a temperature of 800 ° C. or more, at least 5 ° C.
Heat treatment (FIG. 4-108) is performed for at least a minute.

The atmosphere for the heat treatment is preferably an inert gas such as nitrogen, hydrogen or argon, or a mixed gas thereof, but may contain about several percent of oxygen. The heat treatment temperature is more preferably 950 ° C. or higher, if possible.

The effect of stress relaxation by this heat treatment will be described with reference to FIG. In FIG. 3, the horizontal axis represents the oxidation temperature, and the vertical axis represents the residual stress of the silicon substrate after oxidation. The oxidation is performed using a silicon single crystal ((100) plane wafer), and an oxide film having a uniform thickness of 50 nm is formed on the silicon surface.

It can be seen that the residual stress of the silicon substrate monotonously decreases as the oxidation temperature increases. In particular, when a mixed gas of oxygen and hydrogen is used as the oxidizing atmosphere, the stress is remarkably reduced, and decreases to almost zero at 950 ° C. or higher. Such stress relaxation behavior occurs not only in the progress of the oxidation reaction but also when heat treatment is performed after the oxidation reaction is completed. That is, for example, when a mixed gas of oxygen and hydrogen is used as the oxidizing atmosphere, even if an oxide film is formed at 850 ° C. and then heat treatment is performed at 950 ° C. for 30 minutes, the oxide film stress decreases to almost zero. Although the effect of the stress relaxation in the heat treatment process is effective even for about 5 minutes, it is preferable to perform the heat treatment for 20 minutes or more if possible in order to sufficiently relax the stress.

FIG. 3 shows the measurement results when the oxide film thickness is set to 50 nm. When the oxide film thickness is about 100 nm or more, even if the oxide film is oxidized at 950.degree. Does not necessarily decrease to zero. This is because it takes time to relax the stress. Therefore, it is effective to perform the above-described heat treatment after the formation of the oxide film by the thermal oxidation method, or particularly to perform the heat treatment at 1000 ° C. or more (eg, 1200 ° C.) to alleviate the stress in the oxide film. In particular, in the selective oxidation method, stress concentration occurs in the oxide film near the edge of the silicon nitride film. Therefore, such a heat treatment is performed after the silicon nitride film is removed. The generated stress can also be reduced.

In this embodiment, only the silicon nitride film is used as the oxidation protection (prevention) film. However, the oxidation protection (prevention) film has a laminated structure in which a silicon nitride film is deposited on a polycrystalline silicon thin film. No problem. Further, the oxidation protection (prevention) film does not necessarily need to be formed on the pad oxide film 2, but may be directly deposited on the silicon substrate 1. An opening is formed by etching away part of the oxidation protection (prevention) film (FIGS. 4-105 or FIG. 1D).
In this case, the pad oxide film 2 may also be removed to expose the silicon substrate 1, or the silicon substrate 1 may be positively etched from the surface by about 10 nm or more to form a step and expose the silicon substrate 1. No problem.

As described above, in the present embodiment, the stress induced in the oxide film due to the presence of the oxidation-induced stress or the oxidation protection (prevention) film in the selective oxidation method can be reduced, and the structure and electrical reliability of the oxide film can be reduced. There is an effect that can be improved.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a schematic diagram showing a change in the cross section of a silicon substrate in a step of forming a gate oxide film for a MOS transistor using the method for manufacturing a semiconductor device of the present invention, and FIG. 6 is a flowchart showing the manufacturing method of the present embodiment. .

First, according to the flowchart of FIG.
This embodiment will be described with reference to FIG. In this embodiment, FIG.
As shown in (a), a state where the element isolation oxide film 4 has already been formed and the surface of the silicon substrate 1 on which the gate oxide film is to be formed is exposed is an initial state (FIG. 6-202). This element isolation oxide film is preferably formed by using the manufacturing method described in the first embodiment, but is not necessarily limited to this method.

The gate oxide film 6 is formed on the surface of the silicon substrate 1 at, for example, 850 ° C. by using a normal thermal oxidation method (FIG. 5B). After this gate oxidation, the oxide film 4 or 6
Is heat-treated at least at 800 ° C. or more, preferably at 950 ° C. or more, for at least 5 minutes with the surface exposed. The atmosphere for the heat treatment is preferably an inert gas such as nitrogen, hydrogen, or argon, or a mixed gas thereof, but may contain about several percent of oxygen. By this heat treatment, the oxidation-induced stress generated in the oxide film in the process of forming the gate oxide film can be reduced.

In the present embodiment, the stress generated in the oxide film due to the oxidation-induced stress in the gate oxidation process can be reduced, and the structure and the electrical reliability of the oxide film can be improved.

Next, a third embodiment of the present invention will be described with reference to FIGS.
This will be described using. FIG. 7 is a schematic diagram showing a change in the cross section of a silicon substrate in a step of forming a gate electrode for a MOS transistor using the method for manufacturing a semiconductor device of the present invention, and FIG. 8 is a flowchart showing the manufacturing method of the present embodiment. Hereinafter, this embodiment will be described with reference to the flowchart of FIG. 8 and FIG. In this embodiment, up to the gate oxide film 6 of the MOS transistor is formed (FIG. 7).
(A), FIGS. 8-302) are the initial conditions.

The element isolation oxide film 4 and the gate oxide film 6 in this embodiment are preferably formed by using the first embodiment and the second embodiment of the present invention. However, the present invention is not limited to this. Gate electrode 7
For example, a polycrystalline silicon thin film is formed and processed into an electrode shape by etching (FIG. 7B). In this case, since stress concentration occurs in the gate oxide film 6 near the end of the gate electrode 7, at least 800 ° C. or more, preferably 9 ° C. or more, for the purpose of recovering damage received by the oxide film.
Heat treatment at a temperature of 50 ° C. or more for at least 5 minutes or more (FIG. 8-304). The atmosphere for the heat treatment is preferably an inert gas such as nitrogen, hydrogen, or argon, or a mixed gas thereof, but may contain about several percent of oxygen.

The material of the gate electrode is not limited to a polycrystalline silicon thin film. A high melting point metal material, a high melting point metal or a silicide alloy with a metal such as titanium, cobalt, nickel or the like or a laminate of the above thin films is used. A structure may be used. In addition, the present MOS transistor has a DR
It may be used for a memory circuit such as AM or SRAM or an arithmetic circuit.

In the present embodiment, the stress generated in the gate oxide film due to the internal stress of the gate electrode film in the process of forming the gate electrode of the MOS transistor can be reduced, and the structure and electrical reliability of the oxide film can be reduced. There is an effect that it can be improved.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.
This will be described using. FIG. 9 is a schematic view showing a change in the cross section of a silicon substrate in a flash memory structure forming step using the method of manufacturing a semiconductor device of the present invention, and FIG. 10 is a flowchart showing the manufacturing method of the present example.

First, according to the flowchart of FIG.
This embodiment will be described with reference to FIG. In this embodiment, the state in which the element isolation oxide film 4 and the tunnel oxide film 8 are formed on the silicon substrate 1 is an initial state (FIG. 9A, FIG. 10-4).
02). The element isolation film 4 and the tunnel oxide film are:
It is desirable to form by the manufacturing method described in the first embodiment and the second embodiment of the present invention, but it is not necessarily limited to these.

A thin film for a floating electrode is deposited on the tunnel oxide film 8 and processed as a floating electrode 9 by etching (FIG. 9B). The material of the floating electrode 9 may be a polycrystalline silicon or a high melting point metal material, or a silicide alloy with a high melting point metal or a metal such as titanium, cobalt, nickel or a laminated structure of the above thin films. After the formation of the floating electrode, a heat treatment for relaxing the stress caused by the electrode film as described in the third embodiment may be performed.

Next, an insulating film 10 having a silicon oxide film, a silicon nitride film, or a laminated structure thereof is formed on the floating electrode 9. Heat treatment for stress relaxation during the formation of this insulating film (FIG. 1)
0-405) can be performed next. This heat treatment is not necessarily required. Next, a control electrode 11 is formed on the insulating film 10 (FIG. 9D). The material of the control electrode 9 may be a polycrystalline silicon or a high melting point metal material, or a silicide alloy with a high melting point metal or a metal such as titanium, cobalt, nickel or a laminated structure of the above thin films.

After this electrode formation, heat treatment is performed at a temperature of at least 800 ° C. or more, preferably at least 950 ° C. for at least 5 minutes (FIGS. 10-407). The atmosphere for the heat treatment is preferably an inert gas such as nitrogen, hydrogen, or argon, or a mixed gas thereof, but may contain about several percent of oxygen. By this heat treatment, the stress in the insulating film 10 due to the formation of the control electrode 11, the stress in the process of forming the insulating film, or the stress generated in the tunnel oxide film due to the formation of the floating electrode is alleviated.

In this embodiment, the stress generated in the tunnel oxide film or the insulating film between the floating electrode and the control electrode due to the internal stress of the control or floating electrode film in the flash memory structure forming process can be reduced. There is an effect that the structure and electrical reliability of the film or the insulating film can be improved.

[0053]

According to the present invention, a thermal oxide film forming process of a semiconductor device or a stress concentration at an end of a thin film partially deposited on an insulating film having an oxide film or a laminated structure of an oxide film and a nitride film is caused. Since the damaged oxide film can be recovered, the structure and electrical reliability of the oxide film or the insulating film can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a change in the cross-sectional structure of a semiconductor device obtained by a first embodiment of a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a schematic diagram showing a change in cross-sectional structure in a conventional selective oxidation method.

FIG. 3 is a characteristic diagram showing an oxidation temperature dependency of a silicon substrate residual stress after thermal oxidation.

FIG. 4 is a flowchart illustrating a manufacturing process according to the first embodiment of the present invention.

FIG. 5 is a schematic view showing a change in the cross-sectional structure of a semiconductor device obtained by a second embodiment of the method of manufacturing a semiconductor device according to the present invention.

FIG. 6 is a flowchart illustrating a manufacturing process according to a second embodiment of the present invention.

FIG. 7 is a schematic view showing a change in the cross-sectional structure of a semiconductor device obtained by a third embodiment of the method of manufacturing a semiconductor device according to the present invention.

FIG. 8 is a flowchart illustrating a manufacturing process according to a third embodiment of the present invention.

FIG. 9 is a schematic diagram showing a change in the cross-sectional structure of a semiconductor device obtained by a fourth embodiment of the method of manufacturing a semiconductor device according to the present invention.

FIG. 10 is a flowchart illustrating a manufacturing process according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Pad oxide film, 3 ... Silicon nitride film, 4 ... Element isolation oxide film, 5 ... Bird's beak part, 6 ... Gate oxide film, 7 ... Gate electrode, 8 ... Tunnel oxide film, 9
... floating electrodes, 10 ... insulating films, 11 ... control electrodes, 101 ...
Selective oxidation start, 102: silicon substrate, 103: pad oxide film formation, 104: silicon nitride film deposition, 105: silicon nitride film patterning, 106: thermal oxidation, 107: silicon nitride film removal, 108: heat treatment, 109: selective oxidation End, 20
DESCRIPTION OF SYMBOLS 1 ... Start of gate oxide film formation, 202 ... Completion of element isolation oxide film formation, 203 ... Gate oxide film formation, 204 ... Additional heat treatment, 205 ... End of gate oxide film formation, 301 ... Start of gate electrode formation, 302 ... Gate oxide film formation Done, 303 ...
Gate electrode film deposition and processing completed, 304 additional heat treatment,
305 gate electrode formation completed, 401 flash memory structure formation started, 402 tunnel oxide film, element isolation oxide film formation completed, 403 floating electrode formation, 404 insulation film formation, 405 heat treatment, 406 control electrode formation 407
... heat treatment, 408 ... flash memory structure formation completed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Suzuki 5-2-1, Josuihonmachi, Kodaira-shi, Tokyo Inside the Semiconductor Division, Hitachi, Ltd. (72) Inventor Yasuhide Hagiwara 5 of Josuihoncho 5 No. 20-1 Hitachi Semiconductor Co., Ltd.Semiconductor Division (72) Inventor Hiroyuki Ota 502 Kandatecho, Tsuchiura-shi, Ibaraki Pref.Mechanical Research Laboratory, Hitachi, Ltd. Address: Inside Hitachi Mechanical Co., Ltd.

Claims (8)

[Claims] 1. A method of manufacturing a semiconductor device, comprising: performing a heat treatment at a temperature of at least 800 ° C. for at least 5 minutes after forming a thermal oxide film, with the oxide film or the silicon substrate surface being exposed. 2. After selective oxidation in which a partially thick oxide film for electrically insulating and separating semiconductor elements is formed on the surface of the silicon substrate, a thin film other than the oxide film is removed, and the oxide film or the silicon substrate is removed. At least 95 when exposed
A method for manufacturing a semiconductor device, comprising performing heat treatment at a temperature of 0 ° C. or more for 5 minutes or more. 3. A method for forming a gate oxide film of a MOS transistor, comprising: forming a partially thick oxide film on a silicon substrate surface for electrically insulating and isolating semiconductor elements from each other; A method for manufacturing a semiconductor device, comprising: performing heat treatment at a temperature of at least 800 ° C. for at least 5 minutes after forming an electrode. 4. The method according to claim 1, wherein the semiconductor device is a memory device or an arithmetic device. 5. The memory device according to claim 1, wherein the memory device is a flash memory,
5. The method for manufacturing a semiconductor device according to claim 4, wherein the method is selected from a group of AM and SRAM. 6. The method according to claim 1, wherein the thermal oxidation is performed in at least a mixed gas of hydrogen and oxygen or an H2O atmosphere. 7. The heat treatment atmosphere is an inert gas such as nitrogen, hydrogen, or argon, or a mixed gas thereof, or a mixed gas containing about several percent oxygen therein. 7. The method for manufacturing a semiconductor device according to any one of 6. 8. A semiconductor device manufactured by the method according to claim 1.