JP2001060670A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent oxygen contained in an atmosphere of oxygen or in an insulating metal oxide, which forms a capacitor insulating film, from penetrating into a diffusion preventing film from its side. SOLUTION: A protective insulating film 14 is deposited on a field effect transistor provided on a semiconductor substrate 10, and a contact plug 15 whose lower end is connected to the impurity diffused layer 13 is formed in the protective insulating film 14. A diffusion preventing conductive film 16 connected to the upper end of the contact plug 15 is formed on the protective insulating film 14, and a capacitor lower electrode 17 is formed on the diffusion preventing film 16. At least, a sidewall 18 of oxidation inhibiting material is formed on the side of the diffusion preventing film 16, a capacitor insulating film 19 of an insulating metal oxide is formed on the capacitor lower electrode 17 and the sidewall 18, and a capacitor upper electrode 20 is formed on the capacitor insulating film 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device provided with a capacitor having a capacitor insulating film made of an insulating metal oxide such as a ferroelectric film or a high dielectric constant film, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the progress of digital technology, the trend of processing or storing a large amount of data has been promoted, and electronic equipment has been further advanced. As a result, semiconductor integrated circuit devices used in electronic equipment have been developed. The integration of semiconductor devices and miniaturization of semiconductor devices are rapidly progressing.

In order to realize a high integration of a dynamic RAM constituting a semiconductor integrated circuit device, a ferroelectric film is used as a capacitor insulating film instead of a conventionally used silicon oxide or silicon nitride. Alternatively, a technique using a high dielectric constant film has been widely studied and developed.

Also, research and development on ferroelectric films having spontaneous polarization characteristics have been actively conducted with the aim of putting a non-volatile RAM capable of operating at a low voltage and writing or reading at a high speed to practical use.

A conventional semiconductor device provided with a capacitor having a capacitor insulating film made of an insulating metal oxide and a method for manufacturing the same will be described below with reference to FIGS.

First, as shown in FIG. 5A, a gate electrode 1 is formed on a semiconductor substrate 100 with a gate insulating film 101 interposed therebetween.
02, the gate electrode 10 is formed on the semiconductor substrate 100.
Impurity is ion-implanted using 2 as a mask to form an impurity diffusion layer 103 serving as a source region or a drain region of the field-effect transistor. Next, after depositing a protective insulating film 104 over the entire surface of the semiconductor substrate 100, a contact hole is formed in the protective insulating film 104.
By embedding a polysilicon film in the contact hole, a contact plug 105 connected to the impurity diffusion layer 103 is formed.

Next, as shown in FIG. 5B, a laminated film of a titanium nitride film, a lower iridium film, and an upper iridium oxide film is deposited over the entire surface of the protective insulating film 104. Thereafter, by patterning the titanium nitride film and the laminated film, a diffusion preventing film 106 made of the titanium nitride film and a capacitor lower electrode 107 composed of the laminated film are formed.

Next, as shown in FIG. 5C, a capacitor insulating film 108 and an upper capacitor electrode 109 made of an insulating metal oxide are formed so as to cover the lower capacitor electrode 107.
A capacitance element including the capacitance lower electrode 107, the capacitance insulating film 108, and the capacitance upper electrode 109 is obtained.

A conventional semiconductor device and its manufacturing method have the following features.

First, a diffusion preventing film 10 made of titanium nitride is provided between a contact plug 105 and a capacitor lower electrode 107.
6 prevents the contact plug 105 and the capacitor lower electrode 107 from interdiffusion and forming a high-resistance layer in a heat treatment performed later, and also suppresses the capacitance of the capacitor during the manufacturing process. Lower electrode 1
07 can be prevented from being separated from the protective insulating film 104.

Since the diffusion preventing film 106 made of titanium nitride is interposed between the contact plug 105 and the capacitor lower electrode 107, the crystallinity of the insulating metal oxide serving as the capacitor insulating film 108 is improved. In the oxygen atmosphere diffuses in the lower capacitor electrode 107 to reach the diffusion preventing film 106 or oxygen in the insulating metal oxide forming the capacitor insulating film Is diffused in the capacitor lower electrode 107 to reach the diffusion prevention film 106, and titanium nitride constituting the diffusion prevention film 106 is oxidized to form a high-resistance layer, which causes a new problem.

Therefore, the capacitor lower electrode 107 is formed of a laminated film of a lower iridium film and an upper iridium oxide film to prevent oxygen from diffusing in the capacitor lower electrode 107 and reaching the diffusion preventing film 106. are doing.

Further, since a capacitor lower electrode 107 is formed by patterning a laminated film composed of an iridium film and an iridium oxide film and which is easy to be etched, a capacitor insulating film 108 which is difficult to etch is deposited. In addition, it is easy to miniaturize the processing dimensions of the capacitive element, and high integration can be achieved.

[0014]

By the way, we have noticed the following during the process of inspecting the characteristics of the capacitance element of the semiconductor device obtained by the above method. That is, the lower capacitor electrode is formed of a laminated film of an iridium film and an iridium oxide film to prevent oxygen in the atmosphere and oxygen in the insulating metal oxide forming the capacitor insulating film from entering the diffusion preventing film. Despite this, it has been noticed that oxygen penetrates into the diffusion prevention film, thereby deteriorating the characteristics of the capacitive element.

Therefore, as a result of various studies on the reason why oxygen enters the diffusion preventing film, it was found that oxygen enters the diffusion preventing film for the following reasons.

As described above, since the lower capacitor electrode 107 is formed of a laminated film of the lower iridium film and the upper iridium oxide film, oxygen in the oxygen atmosphere diffuses through the lower capacitor electrode 107 during the heat treatment process. Prevention film 1
6, or oxygen in the insulating metal oxide forming the capacitive insulating film 108 can be prevented from diffusing in the capacitive lower electrode 107 and reaching the diffusion preventing film 106. As indicated by the arrows, the oxygen in the oxygen atmosphere or the oxygen in the insulating metal oxide forming the capacitive insulating film 108 is diffused from the side of the diffusion preventing film 106 into the diffusion preventing film 1.
In addition, it has been found that by invading the inside of the substrate 06, the titanium nitride forming the diffusion prevention film 106 is oxidized to form a high resistance layer.

When the high resistance layer is formed inside the diffusion preventing film 106, the contact plug 105 and the diffusion preventing film 106 are formed.
Since the contact resistance with the capacitor insulating film 108 increases, the electric field applied to the capacitive insulating film 108 decreases. For this reason, the electric charge stored in the capacitance insulating film 108 is reduced, which causes a problem that the performance of the capacitance element is reduced.

In view of the above, the present invention prevents the situation in which oxygen in an oxygen atmosphere or oxygen in an insulating metal oxide forming a capacitive insulating film enters the inside of a diffusion preventing film from a side surface of the diffusion preventing film. The purpose is to do.

[0019]

In order to achieve the above object, a semiconductor device according to the present invention comprises a protective insulating film deposited on a semiconductor substrate on which a field effect transistor is formed, and a protective insulating film. A contact plug formed at the lower end and connected to an impurity diffusion layer serving as a source region or a drain region of a field-effect transistor, and a conductive plug formed on a protective insulating film and connected to the upper end of the contact plug. A diffusion prevention film, a sidewall made of an oxidation-resistant material formed at least on the side surface of the diffusion prevention film, a capacitor lower electrode formed on the diffusion prevention film, and formed on the capacitor lower electrode and the sidewall. A capacitor insulating film made of an insulating metal oxide, and a capacitor upper electrode formed on the capacitor insulating film.

According to the semiconductor device of the present invention, an insulating metal oxide film which becomes a capacitive insulating film in a high-temperature oxidizing atmosphere because it has a sidewall made of an oxidation-resistant material and at least covers a side surface of the diffusion prevention film. Even if
Oxygen in the oxidizing atmosphere and oxygen in the insulating metal oxide film hardly diffuse into the sidewall. For this reason, since it is difficult for oxygen to penetrate into the diffusion prevention film, the situation where the diffusion prevention film is oxidized to form a high resistance layer can be prevented.

In the semiconductor device according to the present invention, the sidewall is preferably made of silicon nitride.

As described above, when the sidewall is formed of silicon nitride having extremely high oxidation resistance, oxygen in an oxidizing atmosphere or oxygen in an insulating metal oxide serving as a capacitance insulating film hardly diffuses into the sidewall. Therefore, the situation where the diffusion prevention film is oxidized to form the high resistance layer can be reliably prevented.

In the semiconductor device according to the present invention, it is preferable that the side wall is made of a metal oxide having an insulating property.

In this manner, it is possible to prevent oxygen in the oxidizing atmosphere or oxygen in the insulating metal oxide serving as the capacitive insulating film from diffusing in the sidewall and entering the diffusion preventing film.

In this case, the metal oxide is preferably aluminum oxide, zirconium oxide, iridium oxide, rhodium oxide or ruthenium oxide.

In this case, since it is difficult to generate oxygen from the metal oxide constituting the sidewall, it is possible to prevent a situation where a high resistance layer is formed in the diffusion prevention film due to oxygen in the metal oxide. it can.

In the semiconductor device according to the present invention, the capacitance insulating film is preferably made of a ferroelectric having a bismuth layered perovskite structure, lead zirconate titanate, barium strontium titanate or tantalum pentoxide.

In the semiconductor device according to the present invention, the diffusion preventing film is a single layer having a film made of titanium, tantalum, tungsten, aluminum or an alloy thereof, or a film of titanium, tantalum, tungsten, aluminum or a nitride of these alloys. It is preferable that the film is composed of a film or a laminated film.

With this configuration, it is possible to avoid a situation in which the contact plug and the capacitor lower electrode are mutually diffused to form a high resistance layer, and the capacitor lower electrode of the capacitor is peeled off from the protective insulating film during the manufacturing process. The situation can be prevented.

The method of manufacturing a semiconductor device according to the present invention comprises the steps of: depositing a protective insulating film on a semiconductor substrate on which a field-effect transistor is formed; A step of forming a contact plug so as to be connected to an impurity diffusion layer serving as a source region or a drain region; and a step of forming a conductive diffusion preventing film on a protective insulating film so as to be connected to an upper end of the contact plug. Forming a capacitor lower electrode on the diffusion preventing film; and depositing an oxidation-resistant material film over the entire surface of the protective insulating film including the capacitor lower electrode. Forming a sidewall made of an oxidation-resistant material on at least the side surface of the diffusion prevention film by performing anisotropic dry etching on the capacitor lower electrode and the sidewall of the sidewall. It includes a step of forming a capacitor insulating film made of an insulating metal oxide, and forming a capacitor upper electrode on the capacitor insulating film.

According to the method of manufacturing a semiconductor device according to the present invention, since a sidewall made of an oxidation-resistant material is formed at least on a side surface of a diffusion prevention film, a capacitive insulating film made of an insulating metal oxide is formed. Even if an insulating metal oxide film serving as a capacitive insulating film is formed in a high-temperature oxidizing atmosphere, oxygen in the oxidizing atmosphere and oxygen in the insulating metal oxide film hardly diffuse into the sidewall. This makes it difficult for oxygen to penetrate into the diffusion prevention film, thereby preventing the diffusion prevention film from being oxidized to form a high-resistance layer.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor device according to one embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, a gate electrode 12 is formed on a semiconductor substrate 10 with a gate insulating film 11 interposed therebetween, and a gate electrode 1 on the surface of the semiconductor substrate 10 is formed.
On both sides of the transistor 2, an impurity diffusion layer 13 serving as a source region or a drain region of the field effect transistor is formed.

On the semiconductor substrate 10, a protective insulating film 14 made of, for example, a silicon oxide film is deposited so as to cover the field effect transistor, and the lower end of the protective insulating film 14 has an impurity diffusion layer 13. A contact plug 15 made of a polysilicon film connected to the semiconductor device is buried.

An anti-diffusion film 16 made of a titanium nitride film is provided on the protective insulating film 14, and the anti-diffusion film 16 is connected to the upper end of the contact plug 15.
Further, on the diffusion preventing film 16, a capacitor lower electrode 17 formed of a laminated film of a lower iridium film and an upper iridium oxide film is provided.

The feature of this embodiment is that the diffusion preventing film 16
A sidewall 18 made of silicon nitride is provided on the side surface of the capacitor lower electrode 17 so as to cover the entire side surface of the diffusion prevention film 16 and a part of the side surface of the capacitor lower electrode 17.

On the lower capacitor electrode 17, a capacitor insulating film made of a ferroelectric material such as SrBi ₂ (Ta ₁ -xNb _x ) O ₉ having a bismuth layered perovskite structure so as to cover the lower capacitor electrode 17. The capacitor upper electrode 20 is provided on the capacitor insulating film 19. A capacitance element for data storage is constituted by the capacitance lower electrode 17, the capacitance insulating film 19, and the capacitance upper electrode 20 described above, and a memory cell is constituted by the capacitance element and the above-mentioned field effect transistor. .

The diffusion preventing film 16 made of titanium nitride is used in a heat treatment step performed later to form the contact plug 1.
5 and the capacitor lower electrode 17 are prevented from being mutually diffused to form a high resistance layer, and the capacitor lower electrode 17 is prevented from peeling off from the protective insulating film 14 during the manufacturing process.

The capacitance lower electrode 17 composed of a laminated film of an iridium film and an iridium oxide film is formed by oxygen in an oxygen atmosphere or oxygen in the insulating metal oxide forming the capacitance insulating film 19. Is diffused to prevent diffusion.
To prevent the situation from reaching.

Hereinafter, a method of manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS.
Description will be made with reference to (a) and (b).

First, as shown in FIG. 2A, a gate electrode 12 is formed on a semiconductor substrate 10 with a gate insulating film 11 interposed therebetween.
Is formed, the gate electrode 12 is formed on the semiconductor substrate 10.
The impurity diffusion layer 13 serving as a source region or a drain region of the field-effect transistor is formed by ion-implanting an impurity with the mask as a mask. Next, the semiconductor substrate 1
0, a protective insulating film 14 made of, for example, silicon oxide is deposited so as to cover the field-effect transistor, a contact hole is formed in the protective insulating film 14, and then, for example, a CVD method is used to form a contact hole in the contact hole. By embedding the polysilicon film, the lower end portion becomes the impurity diffusion layer 1.
Then, a contact plug 15 to be connected to 3 is formed.

Next, a titanium nitride film, an iridium film, and an iridium oxide film are sequentially deposited over the entire surface of the protective insulating film 14, and then these films are patterned, as shown in FIG. As described above, the diffusion prevention film 16 made of the titanium nitride film and connected to the upper end of the contact plug 15 is formed, and the capacitor lower electrode 17 made of the laminated film of the iridium film and the iridium oxide film is formed on the diffusion prevention film 16. Form.

Next, as shown in FIG. 2C, after a silicon nitride film 18A is deposited over the entire surface of the protective insulating film 14, the silicon nitride film 18A is deposited on the protective insulating film 14 using an RIE method. By performing isotropic dry etching, as shown in FIG. 3A, the side surfaces of the diffusion prevention film 16 and the capacitor lower electrode 17 are
A sidewall 18 is formed so as to cover the entire side surface of the diffusion prevention film 16 and a part of the side surface of the capacitor lower electrode 17.

Next, as shown in FIG. 3B, an organic metal decomposition method (MOD method) and an organic metal chemical vapor deposition method (MO method)
SrBi ₂ (Ta) having a bismuth layered perovskite structure over the entire lower surface of the capacitor lower electrode 17 and the sidewalls 18 by CVD or sputtering.
_A capacitance insulating film 19 made of a ferroelectric material such as _1-x Nb _x ) O ₉ is formed. Examples of a method for depositing a ferroelectric film include a method in which the ferroelectric film is deposited in a high-temperature oxidizing atmosphere of 500 ° C. or higher, and a method in which a ferroelectric film formed at a low temperature is subjected to a heat treatment in a high-temperature oxidizing atmosphere. Next, when the capacitor upper electrode 20 made of a platinum film is deposited on the capacitor insulating film 19 by sputtering, the semiconductor device according to the present embodiment is obtained.

According to the semiconductor device and the method of manufacturing the same according to the present embodiment, the side wall 18 covering at least the side surface of the diffusion prevention film 16 is provided on the side surface of the diffusion prevention film 16 and the capacitor lower electrode 17. Wall 18
Since the silicon nitride constituting the silicon nitride has extremely high oxidation resistance, even if a ferroelectric film is formed in a high-temperature oxidizing atmosphere, oxygen in the oxidizing atmosphere and oxygen in the ferroelectric film diffuse into the sidewall 18. do not do. For this reason, the oxygen is prevented from diffusing.
6, the titanium nitride constituting the diffusion prevention film 16 is prevented from being oxidized to form a high resistance layer.

FIG. 4 is a diagram comparing the characteristics of the semiconductor device according to the present embodiment with the characteristics of the conventional semiconductor device shown in FIG. 5, and is applied between the semiconductor substrate and the capacitor upper electrode. The relationship between the voltage and the amount of charge (corresponding to the amount of residual polarization) accumulated in the capacitor insulating film is shown.

As can be seen from FIG. 4, in the semiconductor device according to the present embodiment, compared to the conventional semiconductor device, when the applied voltage value is the same, the amount of charge stored in the capacitance insulating film is about 5 times. Doubled. Hereinafter, the reason why the amount of charge stored in the capacitor insulating film is significantly increased will be discussed.

In a conventional semiconductor device, when a ferroelectric film serving as the capacitor insulating film 108 is formed, oxygen in the atmosphere or oxygen in the ferroelectric film enters the inside of the diffusion preventing film 106. Then, a high resistance layer is formed in the diffusion prevention film 106. Therefore, when a voltage is applied between the semiconductor substrate 100 and the capacitor upper electrode 109, part of the applied voltage is applied to the high-resistance layer, and the voltage applied to the capacitor insulating film 108 is reduced. The amount of charge stored is reduced.

On the other hand, in the semiconductor device according to the present embodiment, since the sidewall 18 made of silicon nitride is provided on the side surface of the diffusion prevention film 16, the ferroelectric film serving as the capacitance insulating film 19 is not formed. At the time of film formation, oxygen in the atmosphere or oxygen in the ferroelectric film is blocked by the sidewall 18 and does not enter the inside of the diffusion prevention film 16, so that a high resistance layer is not formed in the diffusion prevention film 16. For this reason, when a voltage is applied between the semiconductor substrate 10 and the capacitor upper electrode 20, the applied voltage is not applied to the high resistance layer, so that the amount of charge stored in the capacitor insulating film 19 is greatly increased.

In the present embodiment, the side wall 18 covers the entire side surface of the diffusion preventing film 16 and a part of the side surface of the capacitor lower electrode 17. May be covered without covering the entire side surface of the diffusion prevention film 16, or may be entirely covered with the diffusion prevention film 16 and each side surface of the capacitor lower electrode.

In this embodiment, the sidewalls 18 are formed of silicon nitride.
Similar effects can be obtained by using other oxidation resistant materials. In this case, when there is a possibility that hydrogen contained in the sidewall 18 diffuses into the capacitive insulating film 19 and reduces the capacitive insulating film 19,
It is preferable to use an insulating oxide containing no hydrogen. In the case where an insulating oxide is used, the insulating oxide is thermally extremely stable in order to avoid decomposition of the insulating oxide to generate oxygen and intrusion of the generated oxygen into the diffusion prevention film 16. , Aluminum oxide, zirconium oxide, iridium oxide, rhodium oxide, ruthenium oxide, or the like is preferably used.

Further, in the present embodiment, the contact plug 15 is formed of polysilicon, but may be replaced with tungsten or the like.

In the present embodiment, the diffusion preventing film 16 is formed of titanium nitride.
A single-layer film or a stacked film including a film made of titanium, tantalum, tungsten, aluminum, an alloy thereof, or a nitride of titanium, tantalum, tungsten, aluminum, or an alloy thereof may be used.
All of the films mentioned here are dense in film quality, have a high function of preventing diffusion, and have excellent adhesion to the protective insulating film 14, but are easily oxidized.

In the present embodiment, the capacitor lower electrode 17 is formed of a laminated film of an iridium film and an iridium oxide film, but instead of platinum, iridium, or the like.
A single-layer film or a stacked film having a film made of ruthenium, rhodium, or an oxide thereof may be used. However, when the ferroelectric film (capacitance insulating film 19) is formed in a high-temperature oxidizing atmosphere, oxygen in the atmosphere or oxygen in the high-dielectric film diffuses in the lower capacitor electrode 17 and the diffusion preventing film 16 To prevent the capacitance from reaching the lower electrode 1
As 7, it is preferable to use a conductive oxide film such as an iridium oxide film having a high oxygen diffusion preventing function as a single-layer film or as a laminated film of a platinum film, an iridium film, a ruthenium film, or a rhodium film.

In the present embodiment, the capacitor upper electrode 20 is formed of a platinum film, but instead of a single-layer film or a stacked film of iridium, ruthenium, rhodium, or a film of these oxides. It may be formed.

Further, in the present embodiment, the capacitor insulating film 19 is formed of a ferroelectric material such as SrBi ₂ (Ta ₁ -xNb _x ) O ₉ , but instead of this, another bismuth layered perovskite structure is used. May be formed of an insulating metal oxide such as a ferroelectric having the above, lead zircon titanate, barium strontium titanate or tantalum pentoxide.

Further, as the semiconductor substrate 10, GaAs
Alternatively, a semi-insulating substrate such as s, a semiconductor substrate having a conductive region formed thereon, a semiconductor substrate having a transistor including an impurity diffusion layer serving as a source or drain region and a gate electrode formed thereon, or the like may be used.

[0058]

According to the semiconductor device or the method of manufacturing the same according to the present invention, after forming a sidewall made of an oxidation-resistant material on a side surface of a diffusion prevention film, a capacitance insulating film made of an insulating metal oxide is formed. Therefore, even if an insulating metal oxide film serving as a capacitive insulating film is formed in a high-temperature oxidizing atmosphere, oxygen in the oxidizing atmosphere and oxygen in the insulating metal oxide film are unlikely to diffuse into the sidewalls, and oxygen is reduced. Since it is difficult to penetrate into the diffusion prevention film, the situation where the diffusion prevention film is oxidized to form a high resistance layer can be prevented. For this reason, when a voltage is applied between the semiconductor substrate and the capacitor upper electrode, the amount of charge stored in the capacitor insulating film is greatly increased, and the characteristics of the capacitor are improved.

[Brief description of the drawings]

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

FIGS. 2A to 2C are cross-sectional views illustrating steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIGS. 3A and 3B are cross-sectional views illustrating steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 4 is a diagram comparing characteristics of the semiconductor device according to the present embodiment with characteristics of a conventional semiconductor device.

FIGS. 5A to 5C are cross-sectional views illustrating respective steps of a conventional method for manufacturing a semiconductor device.

FIG. 6 is a cross-sectional view illustrating a problem of a conventional semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Semiconductor substrate 11 Gate insulating film 12 Gate electrode 13 Impurity diffusion layer 14 Protective insulating film 15 Contact plug 16 Diffusion prevention film 17 Capacitance lower electrode 18 Side wall 19 Capacitive insulating film 20 Capacitance upper electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuhiro Uemoto 1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. F-term (reference) 5F083 FR02 GA09 GA21 JA06 JA14 JA15 JA17 JA38 JA39 JA40 JA43 MA06 MA18 PR03 PR21 PR22

Claims (7)

[Claims] 1. A protective insulating film deposited on a semiconductor substrate on which a field-effect transistor is formed; and a source region or a drain region formed in the protective insulating film and having a lower end portion of the field-effect transistor. A contact plug connected to an impurity diffusion layer to be formed; a conductive diffusion preventing film formed on the protective insulating film and connected to an upper end of the contact plug; and a conductive plug formed at least on a side surface of the diffusion preventing film. A sidewall made of an oxidation-resistant material; a capacitor lower electrode formed on the diffusion prevention film; and a capacitor insulating film made of an insulating metal oxide formed on the capacitor lower electrode and the sidewall. And a capacitor upper electrode formed on the capacitor insulating film. 2. The semiconductor device according to claim 1, wherein said sidewall is made of silicon nitride. 3. The semiconductor device according to claim 1, wherein the sidewall is made of a metal oxide having an insulating property. 4. The method according to claim 1, wherein the metal oxide is aluminum oxide,
The semiconductor device according to claim 3, wherein the semiconductor device is zirconium oxide, iridium oxide, rhodium oxide, or ruthenium oxide. 5. The capacitor insulating film includes a ferroelectric having a bismuth layered perovskite structure, lead zirconate titanate,
2. The semiconductor device according to claim 1, comprising barium strontium titanate or tantalum pentoxide. 6. The anti-diffusion film comprises titanium, tantalum,
2. The semiconductor device according to claim 1, comprising a single-layer film or a laminated film having a film made of tungsten, aluminum, or an alloy thereof, or a nitride of titanium, tantalum, tungsten, aluminum, or an alloy thereof. 7. A step of depositing a protective insulating film on a semiconductor substrate on which a field-effect transistor is formed, wherein a lower end portion of the protective insulating film becomes a source region or a drain region of the field-effect transistor. Forming a contact plug to be connected to the impurity diffusion layer; forming a conductive diffusion preventing film on the protective insulating film so as to be connected to an upper end of the contact plug; Forming a capacitor lower electrode on the film; and depositing an oxidation-resistant material film over the entire surface of the protective insulating film including the capacitor lower electrode. Forming a sidewall made of an oxidation-resistant material on at least a side surface of the diffusion preventing film by performing anisotropic dry etching; Forming a capacitor insulating film made of an insulating metal oxide on the capacitor insulating film, and forming a capacitor upper electrode on the capacitor insulating film. .