Semiconductor device manufacturing method

Abstract

To provide a manufacturing method of a semiconductor device in which a semiconductor layer is formed by oxidizing the semiconductor layer at a low temperature to form a thick oxide film.SOLUTION: A manufacturing method of a semiconductor device according to an embodiment includes forming a first film containing a metal element and oxygen (O) and having a first thickness on a semiconductor layer containing silicon (Si), and forming a second film between the semiconductor layer and the first film, containing silicon (Si) and oxygen (O), and having a second thickness greater than the first thickness by using radical oxidation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a method for manufacturing a semiconductor device. [Background technology]

[0002] In the manufacture of semiconductor devices, it is desirable to have a method for oxidizing semiconductor layers at low temperatures to form thick oxide films. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4719166 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for manufacturing a semiconductor device in which a semiconductor layer is oxidized at a low temperature to form a thick oxide film. [Means for solving the problem]

[0005] In a method for manufacturing a semiconductor device according to an embodiment, a first film containing a metal element and oxygen (O) and having a first thickness is formed on a semiconductor layer containing silicon (Si), and a second film containing silicon (Si) and oxygen (O) and having a second thickness thicker than the first thickness is formed between the semiconductor layer and the first film using radical oxidation. [Brief description of the drawings]

[0006] [Figure 1] 2A to 2C are explanatory views of the method for manufacturing the semiconductor device according to the first embodiment. [Diagram 2] 5A to 5C are explanatory diagrams illustrating the operation and effect of the method for manufacturing the semiconductor device according to the first embodiment. [Diagram 3] 5A to 5C are explanatory views of a method for manufacturing a semiconductor device according to a second embodiment. [Figure 4]8A to 8C are explanatory diagrams illustrating the operation and effect of the method for manufacturing a semiconductor device according to the second embodiment. [Diagram 5] 13 is a schematic cross-sectional view of a semiconductor device manufactured by a method for manufacturing a semiconductor device according to a third embodiment. [Figure 6] 10A to 10C are explanatory diagrams of a manufacturing method of a semiconductor device according to a third embodiment. [Figure 7] 13A to 13C are explanatory diagrams of a modified example of the manufacturing method of the semiconductor device according to the third embodiment. [Figure 8] FIG. 13 is a schematic cross-sectional view of a semiconductor device manufactured by a method for manufacturing a semiconductor device according to a fourth embodiment. [Figure 9] 13A to 13C are explanatory views of a method for manufacturing a semiconductor device according to a fourth embodiment. [Figure 10] FIG. 13 is a schematic cross-sectional view of a semiconductor device manufactured by a manufacturing method of a semiconductor device according to a fifth embodiment. [Figure 11] 13A to 13C are explanatory views of a method for manufacturing a semiconductor device according to a fifth embodiment. [Figure 12] FIG. 13 is a schematic cross-sectional view of a semiconductor device manufactured by a manufacturing method of a semiconductor device according to a sixth embodiment. [Figure 13] 13A to 13C are explanatory views of a manufacturing method of a semiconductor device according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals will be used to designate the same or similar components, and the description of components that have already been described may be omitted as appropriate.

[0008] In addition, the terms "upper" and "lower" may be used for convenience in this specification. "Upper" and "lower" are terms that indicate, for example, a relative positional relationship in a drawing. The terms "upper" and "lower" do not necessarily specify a positional relationship with respect to gravity.

[0009] The qualitative and quantitative analysis of the chemical composition of the members constituting the semiconductor device in this specification can be performed by, for example, secondary ion mass spectrometry (SIMS) or energy dispersive X-ray spectroscopy (EDX). In addition, the thickness of the members constituting the semiconductor device, the distance between the members, etc. can be measured by, for example, a transmission electron microscope (TEM).

[0010] (First embodiment) A method for manufacturing a semiconductor device according to a first embodiment includes forming a first film containing a metal element and oxygen (O) and having a first thickness on a semiconductor layer containing silicon (Si), and using radical oxidation to form a second film containing silicon (Si) and oxygen (O) and having a second thickness thicker than the first thickness between the semiconductor layer and the first film.

[0011] 1(a), 1(b), and 1(c) are explanatory diagrams of a method for manufacturing a semiconductor device according to a first embodiment.

[0012] First, a semiconductor layer 10 is prepared (FIG. 1(a)). The semiconductor layer 10 includes silicon (Si). The semiconductor layer 10 is, for example, mainly composed of silicon (Si). The semiconductor layer 10 is, for example, a single crystal silicon layer or a polycrystalline silicon layer.

[0013] The semiconductor layer 10 is not limited to a single crystal silicon layer or a polycrystalline silicon layer. The semiconductor layer 10 may be, for example, a silicon germanide layer or a silicon carbide layer. In the following, an example in which the semiconductor layer 10 is a single crystal silicon layer will be described.

[0014] Next, an aluminum oxide film 12 is formed on the semiconductor layer 10 (FIG. 1(b)). The aluminum oxide film 12 is an example of a first film. Aluminum (Al) is an example of a metal element.

[0015] The aluminum oxide film 12 is formed by, for example, a chemical vapor deposition method (CVD method) or an atomic layer deposition method (ALD method).

[0016] The first film contains a metal element and oxygen (O). The metal element contained in the first film is, for example, at least one metal element selected from the group consisting of aluminum (Al), hafnium (Hf), zirconium (Zr), lanthanum (La), yttrium (Y), titanium (Ti), nickel (Ni), zinc (Zn), indium (In), tin (Sn), gallium (Ga), and tungsten (W). The first film is, for example, mainly composed of the above metal element and oxygen (O). The first film is, for example, a metal oxide film. The first film is, for example, an oxide film of the above metal element.

[0017] The first film is, for example, an aluminum oxide film, a hafnium oxide film, a zirconium oxide film, a lanthanum oxide film, a yttrium oxide film, a titanium oxide film, a nickel oxide film, a zinc oxide film, an indium oxide film, a tin oxide film, a gallium oxide film, or a tungsten oxide film.

[0018] The first film is, for example, an insulating film or a semiconductor film. The first film is, for example, an amorphous film. The first film contains, for example, at least one element selected from the group consisting of nitrogen (N), carbon (C), hydrogen (H), fluorine (F), and chlorine (Cl).

[0019] The first film has a first thickness (d1 in FIG. 1(b) and FIG. 1(c)). The first thickness d1 is, for example, not less than 1 nm and not more than 5 nm. The first thickness d1 of the aluminum oxide film 12 is, for example, not less than 1 nm and not more than 5 nm.

[0020] The first film is not necessarily limited to an aluminum oxide film, but the following description will be given taking an example in which the first film is an aluminum oxide film.

[0021] Next, a silicon oxide film 14 having a second thickness (d2 in FIG. 1(c)) thicker than the first thickness d1 is formed between the semiconductor layer 10 and the aluminum oxide film 12 by radical oxidation (FIG. 1(c)). The semiconductor layer 10 is oxidized by radical oxidation to form the silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0022] The radical oxidation is carried out in an atmosphere containing oxygen radicals or hydroxyl radicals. For example, the radical oxidation is carried out in an atmosphere in which oxygen gas, hydrogen gas, and argon gas are made into a plasma. For example, the radical oxidation is carried out in an atmosphere in which water vapor is made into a plasma.

[0023] The method for generating oxygen radicals or hydroxyl radicals used in radical oxidation is not particularly limited. For example, oxygen radicals or hydroxyl radicals can be generated using an inductively coupled plasma method, a microwave plasma method, an electron cyclotron resonance method, a helicon wave method, or a hot filament method.

[0024] The radical oxidation atmosphere contains, for example, hydrogen (H) and oxygen (O). The atomic ratio (H / (H+O)) of the hydrogen (H) contained in the radical oxidation atmosphere to the sum of hydrogen (H) and oxygen (O) is, for example, 40% or less. The atomic ratio (H / (H+O)) of the hydrogen (H) contained in the radical oxidation atmosphere to the sum of hydrogen (H) and oxygen (O) is, for example, 2% or more and 5% or less.

[0025] The atomic ratio (H / (H+O)) of hydrogen (H) contained in the radical oxidation atmosphere to the sum of hydrogen (H) and oxygen (O) is adjusted, for example, by the flow rates of hydrogen gas (H2) and oxygen gas (O2) introduced into the radical oxidation atmosphere. The molar ratio (H2 / (H2+O2)) of hydrogen gas (H2) introduced into the radical oxidation atmosphere to the sum of hydrogen gas (H2) and oxygen gas (O2) is, for example, 40% or less. The molar ratio (H2 / (H2+O2)) of hydrogen gas (H2) introduced into the radical oxidation atmosphere to the sum of hydrogen gas (H2) and oxygen gas (O2) is, for example, 2% or more and 5% or less.

[0026] The temperature of the radical oxidation is, for example, 300° C. or more and 900° C. or less. The pressure of the radical oxidation is, for example, 50 Pa or more and 3000 Pa or less.

[0027] The second film contains silicon (Si) and oxygen (O). The second film is mainly composed of, for example, silicon (Si) and oxygen (O).

[0028] The second film has a second thickness (d2 in FIG. 1(c)). The second thickness d2 is thicker than the first thickness d1 of the first film. The second thickness d2 is, for example, 10 times or more the first thickness d1 of the first film. The second thickness d2 is, for example, 10 nm or more and 300 nm or less.

[0029] The second thickness d2 of the silicon oxide film 14 is thicker than the first thickness d1 of the aluminum oxide film 12. The second thickness d2 of the silicon oxide film 14 is, for example, 10 times or more the first thickness d1 of the aluminum oxide film 12. The second thickness d2 of the silicon oxide film 14 is, for example, 10 nm or more and 300 nm or less.

[0030] Next, the operation and effects of the method for manufacturing the semiconductor device according to the first embodiment will be described.

[0031] In the manufacture of semiconductor devices, it is desirable to realize a method for forming a thick oxide film by oxidizing a semiconductor layer at a low temperature. For example, by oxidizing a semiconductor layer at a low temperature, deterioration of the characteristics of a device formed in the semiconductor layer can be suppressed.

[0032] For example, in the manufacture of a semiconductor device including a transistor, if a high-temperature heat treatment is applied after the transistor is formed, the heat treatment may cause impurities to diffuse or the material constituting the transistor to change in quality, which may result in deterioration of the transistor characteristics. If the oxide film can be formed at a low temperature after the transistor is formed, the deterioration of the transistor characteristics can be suppressed.

[0033] The method for manufacturing a semiconductor device according to the first embodiment uses radical oxidation to oxidize a semiconductor layer. By using radical oxidation, it becomes possible to oxidize a semiconductor layer at a lower temperature than, for example, thermal oxidation.

[0034] 2 is an explanatory diagram of the operation and effect of the method for manufacturing a semiconductor device according to the first embodiment, and is a diagram showing the thickness of an oxide film formed by oxidizing a semiconductor layer by radical oxidation.

[0035] Figure 2 is a diagram comparing the oxide film thickness when a second film is formed on a semiconductor layer and when a second film is not formed. Figure 2 shows the case where the semiconductor layer is a single crystal silicon layer and the second film is an aluminum oxide film. Figure 2 shows the case where the aluminum oxide film is 3 nm thick and the temperature of radical oxidation is 700°C.

[0036] 2, when the aluminum oxide film 12 is formed on the semiconductor layer 10 and radical oxidation is performed, the oxide film thickness is seven times or more thicker than when the aluminum oxide film 12 is not formed. In other words, it is found that by forming the aluminum oxide film 12 on the semiconductor layer 10 and performing radical oxidation, a greatly accelerated oxidation occurs.

[0037] The mechanism by which the significantly accelerated oxidation shown in Fig. 2 occurs is not entirely clear. However, it is believed that the presence of a film in which metal elements and oxygen (O) coexist on the silicon-containing semiconductor layer 10 reduces the activation energy for oxide film formation, resulting in accelerated oxidation. It is also believed that oxygen vacancies in the metal oxide are filled with oxygen radicals and hydroxyl radicals, and then the oxygen radicals and hydroxyl radicals that penetrate into the metal oxide expel the oxygen in the metal oxide, resulting in accelerated oxidation.

[0038] In the method for manufacturing a semiconductor device according to the first embodiment, the first film is preferably amorphous, which increases the degree of enhanced oxidation.

[0039] In the method for manufacturing a semiconductor device according to the first embodiment, the first thickness d1 of the first film is preferably 0.5 nm or more, and more preferably 1 nm or more. When the first thickness d1 is 0.5 nm or more, the degree of enhanced oxidation increases, and when the first thickness d1 is 1 nm or more, the degree of enhanced oxidation increases even more.

[0040] In the method for manufacturing a semiconductor device according to the first embodiment, the first thickness d1 of the first film is preferably 5 nm or less, and more preferably 3 nm or less. When the first thickness d1 is 5 nm or less, the degree of enhanced oxidation increases. When the first thickness d1 is 3 nm or less, the degree of enhanced oxidation increases further.

[0041] In the method for manufacturing a semiconductor device according to the first embodiment, the temperature of the radical oxidation is preferably 300° C. or higher, more preferably 400° C. or higher, and further preferably 500° C. or higher. As the temperature of the radical oxidation increases, the degree of accelerated oxidation increases.

[0042] In the method for manufacturing a semiconductor device according to the first embodiment, the temperature of the radical oxidation is preferably 900° C. or less, more preferably 800° C. or less, and further preferably 700° C. or less. By lowering the temperature of the radical oxidation, for example, deterioration of the characteristics of a device formed on a semiconductor layer can be suppressed.

[0043] In the method for manufacturing a semiconductor device according to the first embodiment, the first film preferably contains at least one element selected from the group consisting of nitrogen (N), carbon (C), hydrogen (H), and chlorine (Cl). When the first film contains the above element, crystallization of the first film is suppressed, and the degree of accelerated oxidation is increased.

[0044] In the semiconductor device manufacturing method of the first embodiment, the radical oxidation atmosphere contains hydrogen (H) and oxygen (O), and the atomic ratio (H / (H+O)) of the contained hydrogen (H) to the sum of hydrogen (H) and oxygen (O) is preferably 40% or less, and more preferably 2% or more and 5% or less. By making the atomic ratio (H / (H+O)) fall within the above range, the degree of accelerated oxidation increases.

[0045] As described above, according to the method for manufacturing a semiconductor device of the first embodiment, it is possible to oxidize a semiconductor layer at a low temperature and form a thick oxide film.

[0046] Second Embodiment The method for manufacturing a semiconductor device according to the second embodiment differs from the method for manufacturing a semiconductor device according to the first embodiment in that a third film containing silicon (Si), oxygen (O), and nitrogen (N) is formed on the semiconductor layer before the first film is formed on the semiconductor layer. Hereinafter, some of the contents that overlap with the first embodiment may be omitted.

[0047] 3(a), 3(b), and 3(c) are explanatory diagrams of a method for manufacturing a semiconductor device according to the second embodiment.

[0048] First, the semiconductor layer 10 is prepared (FIG. 3(a)). The semiconductor layer 10 contains silicon (Si). For example, the semiconductor layer 10 is mainly composed of silicon (Si). For example, the semiconductor layer 10 is a single crystal silicon layer or a polycrystalline silicon layer.

[0049] Next, a silicon oxynitride film 16 is formed on the semiconductor layer 10. The silicon oxynitride film 16 is an example of a third film.

[0050] The silicon oxynitride film 16 is formed by, for example, a CVD method.The silicon oxynitride film 16 is formed by, for example, an ALD method.

[0051] The third film contains silicon (Si), oxygen (O), and nitrogen (N). The third film is mainly composed of, for example, silicon (Si), oxygen (O), and nitrogen (N).

[0052] The third film has a thickness of, for example, 1 nm or more and 10 nm or less. The silicon oxynitride film 16 has a thickness of, for example, 1 nm or more and 10 nm or less.

[0053] Next, an aluminum oxide film 12 is formed on the semiconductor layer 10 (FIG. 3(b)). The aluminum oxide film 12 is an example of a first film.

[0054] The first film contains a metal element and oxygen (O). The metal element contained in the first film is, for example, at least one metal element selected from the group consisting of aluminum (Al), hafnium (Hf), zirconium (Zr), lanthanum (La), yttrium (Y), titanium (Ti), nickel (Ni), zinc (Zn), indium (In), tin (Sn), gallium (Ga), and tungsten (W). The first film is, for example, mainly composed of the above metal element and oxygen (O). The first film is, for example, a metal oxide film.

[0055] The first film has a first thickness (d1 in FIGS. 3(b) and 3(c)). The first thickness d1 is, for example, not less than 1 nm and not more than 5 nm. The first thickness d1 of the aluminum oxide film 12 is, for example, not less than 1 nm and not more than 5 nm.

[0056] Next, a silicon oxide film 14 having a second thickness (d2 in FIG. 3(c)) thicker than the first thickness d1 is formed between the semiconductor layer 10 and the aluminum oxide film 12 by radical oxidation (FIG. 3(c)). The silicon oxide film 14 is formed between the semiconductor layer 10 and the silicon oxynitride film 16.

[0057] The semiconductor layer 10 is oxidized by radical oxidation to form a silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0058] The second film contains silicon (Si) and oxygen (O). The second film is mainly composed of, for example, silicon (Si) and oxygen (O).

[0059] The second film has a second thickness (d2 in FIG. 3(c)). The second thickness d2 is thicker than the first thickness d1 of the first film. The second thickness d2 is, for example, 10 times or more the first thickness d1 of the first film. The second thickness d2 is, for example, 10 nm or more and 600 nm or less. The second thickness d2 is thicker than the thickness of the third film.

[0060] The second thickness d2 of the silicon oxide film 14 is thicker than the first thickness d1 of the aluminum oxide film 12. The second thickness d2 of the silicon oxide film 14 is, for example, 10 times or more the first thickness d1 of the aluminum oxide film 12. The second thickness d2 of the silicon oxide film 14 is, for example, 10 nm or more and 600 nm or less. The second thickness d2 is thicker than the thickness of the silicon oxynitride film 16.

[0061] Next, the operation and effects of the method for manufacturing the semiconductor device according to the second embodiment will be described.

[0062] 4 is an explanatory diagram of the operation and effect of the method for manufacturing a semiconductor device according to the second embodiment, and is a diagram showing the thickness of an oxide film formed by oxidizing a semiconductor layer by radical oxidation.

[0063] Fig. 4 is a diagram comparing the oxide film thickness when the third film and the second film are formed on the semiconductor layer, when only the second film is formed, and when the third film and the second film are not formed. Fig. 4 shows the case where the semiconductor layer is a single crystal silicon layer, the third film is a silicon oxynitride film, and the second film is an aluminum oxide film. Fig. 4 shows the case where the silicon oxynitride film is 8 nm thick, the aluminum oxide film is 3 nm thick, and the temperature of radical oxidation is 700°C.

[0064] 4, when the silicon oxynitride film 16 and the aluminum oxide film 12 are formed on the semiconductor layer 10 and radical oxidation is performed, the oxide film thickness is 26 times or more larger than when the silicon oxynitride film 16 and the aluminum oxide film 12 are not formed. Also, when the silicon oxynitride film 16 and the aluminum oxide film 12 are formed on the semiconductor layer 10 and radical oxidation is performed, the oxide film thickness is three times or more larger than when only the aluminum oxide film 12 is formed and radical oxidation is performed. It can be seen that by forming the silicon oxynitride film 16 and the aluminum oxide film 12 on the semiconductor layer 10 and performing radical oxidation, a significantly accelerated oxidation occurs.

[0065] As described above, according to the method for manufacturing a semiconductor device of the second embodiment, it is possible to form a thick oxide film by oxidizing a semiconductor layer at a low temperature.

[0066] (Third embodiment) A method for manufacturing a semiconductor device according to a third embodiment includes forming a first film having a first thickness and including a first metal element and oxygen (O) on at least a first region of a semiconductor layer including silicon (Si) and including a first region and a second region, and forming a second film between the first region and the first film and on the second region using radical oxidation, the second film including silicon (Si) and oxygen (O), the second thickness on the first region being thicker than the first thickness, and the third thickness on the second region being thinner than the second thickness. The first film is selectively formed on the first region. In the following, some of the contents overlapping with the first embodiment may be omitted.

[0067] 5 is a schematic cross-sectional view of a semiconductor device manufactured by the semiconductor device manufacturing method of the third embodiment. The semiconductor device includes a first transistor 100 and a second transistor 200. The first transistor 100 and the second transistor 200 are Metal Oxide Field Effect Transistors (MOSFETs).

[0068] The first transistor 100 includes a semiconductor layer 10, a first gate insulating layer 101, and a first gate electrode 102. The semiconductor layer 10 includes a first p-type semiconductor region 10a and an n-type semiconductor region 10x. The first gate insulating layer 101 includes a first lower film 101a and a first upper film 101b.

[0069] The semiconductor layer 10 is, for example, a single crystal silicon layer. A portion of the first p-type semiconductor region 10a facing the first gate electrode 102 functions as a channel region of the first transistor 100. The n-type semiconductor region 10x functions as a source / drain region of the first transistor 100.

[0070] The first lower film 101a of the first gate insulating layer 101 contains silicon (Si) and oxygen (O). The first lower film 101a is, for example, a silicon oxide film. The first upper film 101b of the first gate insulating layer 101 contains a first metal element and oxygen (O). The first upper film 101b is, for example, an aluminum oxide film. Aluminum (Al) is an example of the first metal element.

[0071] The first gate electrode 102 is a conductor and is, for example, polycrystalline silicon containing p-type impurities or n-type impurities.

[0072] The second transistor 200 includes a semiconductor layer 10, a second gate insulating layer 201, and a second gate electrode 202. The semiconductor layer 10 includes a second p-type semiconductor region 10b and an n-type semiconductor region 10x.

[0073] A portion of the second p-type semiconductor region 10b facing the second gate electrode 202 functions as a channel region of the second transistor 200. The n-type semiconductor region 10x functions as a source / drain region of the second transistor 200.

[0074] The second gate insulating layer 201 contains silicon (Si) and oxygen (O). The second gate insulating layer 201 is, for example, a silicon oxide film.

[0075] The second gate electrode 202 is a conductor and is, for example, polycrystalline silicon containing p-type impurities or n-type impurities.

[0076] The thickness of the first gate insulating layer 101 of the first transistor 100 is greater than the thickness of the second gate insulating layer 201 of the second transistor 200 .

[0077] Because the first gate insulating layer 101 of the first transistor 100 is thicker than the second gate insulating layer 201 of the second transistor 200, for example, it is possible to operate the first transistor 100 at a higher driving voltage than the second transistor 200.

[0078] 6(a), 6(b), 6(c), and 6(d) are explanatory diagrams of a method for manufacturing a semiconductor device according to the third embodiment.

[0079] First, the semiconductor layer 10 is prepared (FIG. 6(a)). The semiconductor layer 10 contains silicon (Si). The semiconductor layer 10 is, for example, mainly composed of silicon (Si). The semiconductor layer 10 is, for example, a single crystal silicon layer or a polycrystalline silicon layer.

[0080] The semiconductor layer 10 is not limited to a single crystal silicon layer or a polycrystalline silicon layer. The semiconductor layer 10 may be, for example, a silicon germanide layer or a silicon carbide layer. In the following, an example in which the semiconductor layer 10 is a single crystal silicon layer will be described.

[0081] The semiconductor layer 10 includes a first p-type semiconductor region 10a and a second p-type semiconductor region 10b.

[0082] Next, an aluminum oxide film 12 is formed on the semiconductor layer 10 (FIG. 6(b)). The aluminum oxide film 12 is an example of a first film. A part of the aluminum oxide film 12 will eventually become the first upper film 101b. Aluminum (Al) is an example of a first metallic element.

[0083] The aluminum oxide film 12 is formed by, for example, a CVD method or an ALD method.

[0084] The first film contains a first metal element and oxygen (O). The first metal element contained in the first film is, for example, at least one metal element selected from the group consisting of aluminum (Al), hafnium (Hf), zirconium (Zr), lanthanum (La), yttrium (Y), titanium (Ti), nickel (Ni), zinc (Zn), indium (In), tin (Sn), gallium (Ga), and tungsten (W). The first film is, for example, mainly composed of the first metal element and oxygen (O). The first film is, for example, a metal oxide film. The first film is, for example, an oxide film of the first metal element.

[0085] The first film is, for example, an insulating film or a semiconductor film. The first film is, for example, an amorphous film. The first film contains, for example, at least one element selected from the group consisting of nitrogen (N), carbon (C), hydrogen (H), and chlorine (Cl).

[0086] The first film has a first thickness (d1 in FIG. 6(b)). The first thickness d1 is, for example, not less than 1 nm and not more than 5 nm. The first thickness d1 of the aluminum oxide film 12 is, for example, not less than 1 nm and not more than 5 nm.

[0087] The first film is not necessarily limited to an aluminum oxide film, but the following description will be given taking an example in which the first film is an aluminum oxide film.

[0088] Next, the aluminum oxide film 12 on the second p-type semiconductor region 10b is removed (FIG. 6(c)). The aluminum oxide film 12 on the second p-type semiconductor region 10b is removed by, for example, a wet etching method. By removing the aluminum oxide film 12 on the second p-type semiconductor region 10b, the aluminum oxide film 12 is selectively formed on the first p-type semiconductor region 10a.

[0089] Next, a silicon oxide film 14 is formed on the semiconductor layer 10 by radical oxidation (FIG. 6(d)). The silicon oxide film 14 is formed on the first p-type semiconductor region 10a. The silicon oxide film 14 is formed between the first p-type semiconductor region 10a and the aluminum oxide film 12. The silicon oxide film 14 is formed on the second p-type semiconductor region 10b.

[0090] The silicon oxide film 14 on the first p-type semiconductor region 10a will eventually become the first lower film 101a, and the silicon oxide film 14 on the second p-type semiconductor region 10b will eventually become the second gate insulating layer 201.

[0091] A second thickness (d2 in FIG. 6(d)) of the silicon oxide film 14 between the first p-type semiconductor region 10a and the aluminum oxide film 12 is thicker than the first thickness d1 of the aluminum oxide film 12. A third thickness (d3 in FIG. 6(d)) of the silicon oxide film 14 on the second p-type semiconductor region 10b is thinner than the second thickness d2 of the silicon oxide film 14.

[0092] The semiconductor layer 10 is oxidized by radical oxidation to form a silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0093] Due to the enhanced oxidation, the silicon oxide film 14 on the first p-type semiconductor region 10a becomes thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0094] The radical oxidation is carried out in an atmosphere containing oxygen radicals or hydroxyl radicals. For example, the radical oxidation is carried out in an atmosphere in which oxygen gas, hydrogen gas, and argon gas are made into a plasma. For example, the radical oxidation is carried out in an atmosphere in which water vapor is made into a plasma.

[0095] The method for generating oxygen radicals or hydroxyl radicals used in radical oxidation is not particularly limited. For example, oxygen radicals or hydroxyl radicals can be generated using an inductively coupled plasma method, a microwave plasma method, an electron cyclotron resonance method, a helicon wave method, or a hot filament method.

[0096] The radical oxidation atmosphere contains, for example, hydrogen (H) and oxygen (O). The atomic ratio (H / (H+O)) of the hydrogen (H) contained in the radical oxidation atmosphere to the sum of hydrogen (H) and oxygen (O) is, for example, 40% or less. The atomic ratio (H / (H+O)) of the hydrogen (H) contained in the radical oxidation atmosphere to the sum of hydrogen (H) and oxygen (O) is, for example, 2% or more and 5% or less.

[0097] The atomic ratio (H / (H+O)) of hydrogen (H) contained in the radical oxidation atmosphere to the sum of hydrogen (H) and oxygen (O) is adjusted, for example, by the flow rates of hydrogen gas (H2) and oxygen gas (O2) introduced into the radical oxidation atmosphere. The molar ratio (H2 / (H2+O2)) of hydrogen gas (H2) introduced into the radical oxidation atmosphere to the sum of hydrogen gas (H2) and oxygen gas (O2) is, for example, 40% or less. The molar ratio (H2 / (H2+O2)) of hydrogen gas (H2) introduced into the radical oxidation atmosphere to the sum of hydrogen gas (H2) and oxygen gas (O2) is, for example, 2% or more and 5% or less.

[0098] The temperature of the radical oxidation is, for example, 300° C. or more and 900° C. or less. The pressure of the radical oxidation is, for example, 50 Pa or more and 3000 Pa or less.

[0099] The second film contains silicon (Si) and oxygen (O). The second film is mainly composed of, for example, silicon (Si) and oxygen (O).

[0100] The second film on the first p-type semiconductor region 10a has a second thickness (d2 in FIG. 6(d)). The second film on the second p-type semiconductor region 10b has a third thickness (d3 in FIG. 6(d)).

[0101] The second thickness d2 is thicker than the first thickness d1 of the first film. The second thickness d2 is, for example, 10 times or more the first thickness d1 of the first film. The second thickness d2 is, for example, 10 nm or more and 300 nm or less.

[0102] The second thickness d2 of the silicon oxide film 14 is thicker than the first thickness d1 of the aluminum oxide film 12. The second thickness d2 of the silicon oxide film 14 is, for example, 10 times or more the first thickness d1 of the aluminum oxide film 12. The second thickness d2 of the silicon oxide film 14 is, for example, 10 nm or more and 300 nm or less.

[0103] The second thickness d2 is greater than the third thickness d3. The second thickness d2 is, for example, seven times or more the third thickness d3.

[0104] The second thickness d2 of the silicon oxide film 14 is thicker than the third thickness d3 of the silicon oxide film 14. The second thickness d2 of the silicon oxide film 14 is, for example, seven times or more the third thickness d3 of the silicon oxide film 14.

[0105] Thereafter, the first gate electrode 102, the second gate electrode 202, and the n-type semiconductor region 10x are formed using a known process technology, thereby manufacturing the semiconductor device shown in Fig. 5. The first gate electrode 102 is formed above the silicon oxide film 14 on the first p-type semiconductor region 10a. The second gate electrode 202 is formed above the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0106] (Modification) The modified example of the method for manufacturing a semiconductor device of the third embodiment differs from the method for manufacturing a semiconductor device of the third embodiment in that a third film containing silicon (Si), oxygen (O), and nitrogen (N) is formed on the first region before forming the first film.

[0107] 7(a), 7(b), 7(c), and 7(d) are explanatory views of a modified example of the method for manufacturing the semiconductor device according to the third embodiment.

[0108] First, a semiconductor layer 10 is prepared (FIG. 7(a)). The semiconductor layer 10 includes a first p-type semiconductor region 10a and a second p-type semiconductor region 10b.

[0109] Next, a silicon oxynitride film 16 is formed on the semiconductor layer 10. The silicon oxynitride film 16 is an example of a third film. Next, an aluminum oxide film 12 is formed on the semiconductor layer 10 (FIG. 7(b)). The aluminum oxide film 12 is an example of a first film.

[0110] Next, the silicon oxynitride film 16 and the aluminum oxide film 12 on the second p-type semiconductor region 10b are removed (FIG. 7(c)). The silicon oxynitride film 16 and the aluminum oxide film 12 on the second p-type semiconductor region 10b are removed by, for example, a wet etching method. By removing the silicon oxynitride film 16 and the aluminum oxide film 12 on the second p-type semiconductor region 10b, the silicon oxynitride film 16 and the aluminum oxide film 12 are selectively formed on the first p-type semiconductor region 10a.

[0111] Next, a silicon oxide film 14 is formed on the semiconductor layer 10 by radical oxidation (FIG. 7(d)). The silicon oxide film 14 is formed on the first p-type semiconductor region 10a. The silicon oxide film 14 is formed on the second p-type semiconductor region 10b.

[0112] The semiconductor layer 10 is oxidized by radical oxidation to form a silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0113] The silicon oxide film 14 on the first p-type semiconductor region 10a becomes thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b due to the accelerated oxidation. In particular, the provision of the silicon oxynitride film 16 on the first p-type semiconductor region 10a promotes the accelerated oxidation compared to the manufacturing method of the semiconductor device of the third embodiment. Therefore, compared to the manufacturing method of the semiconductor device of the third embodiment, it is easier to make the second thickness (d2 in FIG. 7(b)) of the silicon oxide film 14 on the first p-type semiconductor region 10a thicker than the third thickness (d3 in FIG. 7(b)) of the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0114] Thereafter, the first gate electrode 102, the second gate electrode 202, and the n-type semiconductor region 10x are formed using a known process technology, thereby manufacturing a semiconductor device similar to that shown in FIG.

[0115] As described above, according to the method for manufacturing a semiconductor device of the third embodiment and its modified example, it is possible to oxidize a semiconductor layer at a low temperature and form oxide films with different thicknesses on the semiconductor layer.

[0116] (Fourth embodiment) In the manufacturing method of the semiconductor device of the fourth embodiment, before forming the first film, a third film containing silicon (Si), oxygen (O), and nitrogen (N) is formed on the first region. In the following, some of the contents that overlap with the third embodiment may be omitted.

[0117] 8 is a schematic cross-sectional view of a semiconductor device manufactured by the method for manufacturing a semiconductor device according to the fourth embodiment. The semiconductor device includes a first transistor 100 and a second transistor 200. The first transistor 100 and the second transistor 200 are MOSFETs.

[0118] The first transistor 100 includes a semiconductor layer 10, a first gate insulating layer 101, and a first gate electrode 102. The semiconductor layer 10 includes a first p-type semiconductor region 10a and an n-type semiconductor region 10x. The first gate insulating layer 101 includes a first lower film 101a, an intermediate film 101c, and a first upper film 101b.

[0119] The first transistor 100 of the fourth embodiment differs from the first transistor 100 of the third embodiment in that the first gate insulating layer 101 includes an intermediate film 101c.

[0120] The first lower film 101a of the first gate insulating layer 101 contains silicon (Si) and oxygen (O). The first lower film 101a is, for example, a silicon oxide film. The intermediate film 101c of the first gate insulating layer 101 contains silicon (Si), oxygen (O), and nitrogen (N). The intermediate film 101c is, for example, a silicon oxynitride film. The first upper film 101b of the first gate insulating layer 101 contains a first metal element and oxygen (O). The first upper film 101b is, for example, an aluminum oxide film.

[0121] The second transistor 200 includes a semiconductor layer 10, a second gate insulating layer 201, and a second gate electrode 202. The semiconductor layer 10 includes a second p-type semiconductor region 10b and an n-type semiconductor region 10x. The second gate insulating layer 201 includes a second lower film 201a and a second upper film 201b.

[0122] The second gate insulating layer 201 contains silicon (Si) and oxygen (O). The second lower film 201a of the second gate insulating layer 201 is, for example, a silicon oxide film. The second upper film 201b of the second gate insulating layer 201 contains a first metal element and oxygen (O). The second upper film 201b is, for example, an aluminum oxide film.

[0123] The thickness of the first gate insulating layer 101 of the first transistor 100 is greater than the thickness of the second gate insulating layer 201 of the second transistor 200 .

[0124] 9(a), 9(b), 9(c), and 9(d) are explanatory views of a method for manufacturing a semiconductor device according to the fourth embodiment.

[0125] First, a semiconductor layer 10 is prepared (FIG. 9(a)). The semiconductor layer 10 includes a first p-type semiconductor region 10a and a second p-type semiconductor region 10b.

[0126] Next, a silicon oxynitride film 16 is formed on the semiconductor layer 10. The silicon oxynitride film 16 is an example of a third film. Next, the silicon oxynitride film 16 on the second p-type semiconductor region 10b is removed (FIG. 9(b)). The silicon oxynitride film 16 is selectively formed on the first p-type semiconductor region 10a. The silicon oxynitride film 16 will eventually become the intermediate film 101c.

[0127] Next, an aluminum oxide film 12 is formed on the semiconductor layer 10 (FIG. 9(c)). The aluminum oxide film 12 is an example of a first film. A part of the aluminum oxide film 12 will eventually become the first upper film 101b. Another part of the aluminum oxide film 12 will eventually become the second upper film 201b.

[0128] Next, a silicon oxide film 14 is formed on the semiconductor layer 10 by radical oxidation (FIG. 9(d)). The silicon oxide film 14 is formed on the first p-type semiconductor region 10a. The silicon oxide film 14 is formed on the second p-type semiconductor region 10b.

[0129] The silicon oxide film 14 on the first p-type semiconductor region 10a will eventually become the first lower film 101a, and the silicon oxide film 14 on the second p-type semiconductor region 10b will eventually become the second lower film 201a.

[0130] The second thickness (d2 in FIG. 9(d)) of the silicon oxide film 14 between the first p-type semiconductor region 10a and the aluminum oxide film 12 is thicker than the first thickness (d1 in FIGS. 9(c) and 9(d)) of the aluminum oxide film 12. The third thickness (d3 in FIG. 9(d)) of the silicon oxide film 14 on the second p-type semiconductor region 10b is thinner than the second thickness d2 of the silicon oxide film 14.

[0131] The semiconductor layer 10 is oxidized by radical oxidation to form a silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0132] Due to the enhanced oxidation, the silicon oxide film 14 on the first p-type semiconductor region 10a becomes thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0133] Thereafter, the first gate electrode 102, the second gate electrode 202, and the n-type semiconductor region 10x are formed using a known process technology, thereby completing the manufacture of the semiconductor device shown in FIG.

[0134] As described above, according to the method for manufacturing a semiconductor device of the fourth embodiment, it is possible to oxidize a semiconductor layer at a low temperature and form oxide films with different thicknesses on the semiconductor layer.

[0135] Fifth embodiment The method for manufacturing a semiconductor device of the fifth embodiment differs from the method for manufacturing a semiconductor device of the third embodiment in that a fourth film containing a second metal element different from the first metal element and oxygen (O) and having a fourth thickness is formed on the second region before forming the first film or after forming the first film and before forming the second film, and the third thickness is thicker than the fourth thickness. Hereinafter, some of the contents that overlap with the third embodiment may be omitted.

[0136] 10 is a schematic cross-sectional view of a semiconductor device manufactured by the semiconductor device manufacturing method of the fifth embodiment. The semiconductor device includes a first transistor 100 and a second transistor 200. The first transistor 100 and the second transistor 200 are MOSFETs.

[0137] The first transistor 100 includes a semiconductor layer 10, a first gate insulating layer 101, and a first gate electrode 102. The semiconductor layer 10 includes a first p-type semiconductor region 10a and an n-type semiconductor region 10x. The first gate insulating layer 101 includes a first lower film 101a and a first upper film 101b.

[0138] The first lower film 101a of the first gate insulating layer 101 contains silicon (Si) and oxygen (O). The first lower film 101a is, for example, a silicon oxide film. The first lower film 101a is, for example, a silicon oxide film. The first upper film 101b of the first gate insulating layer 101 contains a first metal element and oxygen (O). The first upper film 101b is, for example, an aluminum oxide film. Aluminum (Al) is an example of the first metal element.

[0139] The second transistor 200 includes a semiconductor layer 10, a second gate insulating layer 201, and a second gate electrode 202. The semiconductor layer 10 includes a second p-type semiconductor region 10b and an n-type semiconductor region 10x. The second gate insulating layer 201 includes a second lower film 201a and a second upper film 201b.

[0140] The second transistor 200 of the fifth embodiment differs from the second transistor 200 of the third embodiment in that the second gate insulating layer 201 includes a second lower film 201a and a second upper film 201b.

[0141] The second gate insulating layer 201 includes silicon (Si) and oxygen (O). The second lower film 201a of the second gate insulating layer 201 is, for example, a silicon oxide film. The second upper film 201b of the second gate insulating layer 201 includes a second metal element different from the first metal element and oxygen (O). The second upper film 201b is, for example, a hafnium oxide film. Hafnium (Hf) is an example of the second metal element.

[0142] The thickness of the first gate insulating layer 101 of the first transistor 100 is greater than the thickness of the second gate insulating layer 201 of the second transistor 200 .

[0143] 11(a), 11(b), 11(c), and 11(d) are explanatory views of the method for manufacturing the semiconductor device according to the fifth embodiment.

[0144] First, a semiconductor layer 10 is prepared (FIG. 11(a)). The semiconductor layer 10 includes a first p-type semiconductor region 10a and a second p-type semiconductor region 10b.

[0145] Next, an aluminum oxide film 12 is formed on the first p-type semiconductor region 10a of the semiconductor layer 10 (FIG. 11(b)). The aluminum oxide film 12 is an example of a first film. The aluminum oxide film 12 will eventually become the first upper film 101b. Aluminum (Al) is an example of the first metal element.

[0146] The first film has a first thickness (d1 in FIG. 11(b)). The aluminum oxide film 12 has a first thickness d1.

[0147] Next, a hafnium oxide film 18 is formed on the second p-type semiconductor region 10b of the semiconductor layer 10. The hafnium oxide film 18 is an example of a fourth film. The hafnium oxide film 18 is selectively formed on the second p-type semiconductor region 10b. The hafnium oxide film 18 eventually becomes the second upper film 201b.

[0148] The fourth film contains a second metal element different from the first metal element and oxygen (O). Hafnium (Hf) is an example of the second metal element.

[0149] The fourth film has a fourth thickness (d4 in FIGS. 11(c) and 11(d)). The hafnium oxide film 18 has a fourth thickness d4.

[0150] The fourth film may be formed before the first film is formed. For example, the hafnium oxide film 18 may be formed before the aluminum oxide film 12 is formed, thereby manufacturing the structure shown in FIG.

[0151] Next, a silicon oxide film 14 is formed on the semiconductor layer 10 by radical oxidation (FIG. 11(d)). The silicon oxide film 14 is formed on the first p-type semiconductor region 10a. The silicon oxide film 14 is formed on the second p-type semiconductor region 10b.

[0152] The semiconductor layer 10 is oxidized by radical oxidation to form a silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0153] The silicon oxide film 14 on the first p-type semiconductor region 10a will eventually become the first lower film 101a, and the silicon oxide film 14 on the second p-type semiconductor region 10b will eventually become the second lower film 201a.

[0154] The second thickness (d2 in FIG. 11(d)) of the silicon oxide film 14 between the first p-type semiconductor region 10a and the aluminum oxide film 12 is thicker than the first thickness d1 of the aluminum oxide film 12. The third thickness (d3 in FIG. 11(d)) of the silicon oxide film 14 on the second p-type semiconductor region 10b is thinner than the second thickness d2 of the silicon oxide film 14. The third thickness d3 of the silicon oxide film 14 on the second p-type semiconductor region 10b is thicker than the fourth thickness d4 of the hafnium oxide film 18.

[0155] Due to the enhanced oxidation, the silicon oxide film 14 on the first p-type semiconductor region 10a becomes thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0156] The degree of enhanced oxidation varies depending on the type of metal element contained in the film formed on the semiconductor layer 10 before radical oxidation. For example, when the film contains aluminum (Al), enhanced oxidation is promoted more than when the film contains hafnium (Hf). Also, for example, when the film contains hafnium (Hf), enhanced oxidation is promoted more than when the film contains zirconium (Zr). Also, for example, when the film contains zirconium (Zr), enhanced oxidation is promoted more than when the film contains titanium (Ti).

[0157] The degree of enhanced oxidation varies depending on the type of film formed on the semiconductor layer 10 before radical oxidation. For example, when the film is an aluminum oxide film, the enhanced oxidation is promoted more than when the film is a hafnium oxide film. Also, for example, when the film is a hafnium oxide film, the enhanced oxidation is promoted more than when the film is a zirconium oxide film. Also, for example, when the film is a zirconium oxide film, the enhanced oxidation is promoted more than when the film is a titanium oxide film.

[0158] In the manufacturing method of the semiconductor device of the fifth embodiment, the first film is the aluminum oxide film 12 and the fourth film is the hafnium oxide film 18, so that the accelerated oxidation of the first p-type semiconductor region 10a is promoted more rapidly than the accelerated oxidation of the second p-type semiconductor region 10b. Therefore, the silicon oxide film 14 on the first p-type semiconductor region 10a becomes thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0159] Thereafter, the first gate electrode 102, the second gate electrode 202, and the n-type semiconductor region 10x are formed using a known process technology, thereby completing the manufacture of the semiconductor device shown in FIG.

[0160] As described above, according to the method for manufacturing a semiconductor device of the fifth embodiment, it is possible to oxidize a semiconductor layer at a low temperature and form oxide films with different thicknesses on the semiconductor layer.

[0161] Sixth embodiment The method for manufacturing a semiconductor device according to the sixth embodiment differs from the method for manufacturing a semiconductor device according to the third embodiment in that a first film is also formed on the second region, and the thickness of the first film on the second region is different from the thickness of the first film on the first region. Hereinafter, some of the contents that overlap with the third embodiment may be omitted.

[0162] 12 is a schematic cross-sectional view of a semiconductor device manufactured by the semiconductor device manufacturing method of the sixth embodiment. The semiconductor device includes a first transistor 100 and a second transistor 200. The first transistor 100 and the second transistor 200 are MOSFETs.

[0163] The first transistor 100 includes a semiconductor layer 10, a first gate insulating layer 101, and a first gate electrode 102. The semiconductor layer 10 includes a first p-type semiconductor region 10a and an n-type semiconductor region 10x. The first gate insulating layer 101 includes a first lower film 101a and a first upper film 101b.

[0164] The first lower film 101a of the first gate insulating layer 101 contains silicon (Si) and oxygen (O). The first lower film 101a is, for example, a silicon oxide film. The first lower film 101a is, for example, a silicon oxide film. The first upper film 101b of the first gate insulating layer 101 contains a first metal element and oxygen (O). The first upper film 101b is, for example, an aluminum oxide film. Aluminum (Al) is an example of the first metal element.

[0165] The second transistor 200 includes a semiconductor layer 10, a second gate insulating layer 201, and a second gate electrode 202. The semiconductor layer 10 includes a second p-type semiconductor region 10b and an n-type semiconductor region 10x. The second gate insulating layer 201 includes a second lower film 201a and a second upper film 201b.

[0166] The second transistor 200 of the sixth embodiment differs from the second transistor 200 of the third embodiment in that the second gate insulating layer 201 includes a second lower film 201a and a second upper film 201b.

[0167] The second gate insulating layer 201 contains silicon (Si) and oxygen (O). The second lower film 201a of the second gate insulating layer 201 is, for example, a silicon oxide film. The second upper film 201b of the second gate insulating layer 201 contains a first metal element and oxygen (O). The second upper film 201b is, for example, an aluminum oxide film. Aluminum (Al) is an example of the first metal element.

[0168] The thickness of the first gate insulating layer 101 of the first transistor 100 is thicker than the thickness of the second gate insulating layer 201 of the second transistor 200. The thickness of the first upper film 101b of the first transistor 100 is different from the thickness of the second upper film 201b of the second transistor 200. The thickness of the first upper film 101b of the first transistor 100 is thinner than the thickness of the second upper film 201b of the second transistor 200.

[0169] 13(a), 13(b), 13(c), and 13(d) are explanatory diagrams of a method for manufacturing a semiconductor device according to the sixth embodiment.

[0170] First, a semiconductor layer 10 is prepared (FIG. 13(a)). The semiconductor layer 10 includes a first p-type semiconductor region 10a and a second p-type semiconductor region 10b.

[0171] Next, an aluminum oxide film 12 is selectively formed on the second p-type semiconductor region 10b of the semiconductor layer 10 (FIG. 13(b)).

[0172] Next, an aluminum oxide film 12 is formed on the first p-type semiconductor region 10a and the second p-type semiconductor region 10b of the semiconductor layer 10 (FIG. 13(c)). As a result, the thickness (d1' in FIG. 13(b)) of the aluminum oxide film 12 on the second p-type semiconductor region 10b becomes thicker than the thickness (d1 in FIG. 13(b)) of the aluminum oxide film 12 on the first p-type semiconductor region 10a.

[0173] The aluminum oxide film 12 is an example of a first film. The aluminum oxide film 12 on the first p-type semiconductor region 10a will eventually become a first upper film 101b. The aluminum oxide film 12 on the second p-type semiconductor region 10b will eventually become a second upper film 201b. Aluminum (Al) is an example of a first metal element.

[0174] Next, a silicon oxide film 14 is formed on the semiconductor layer 10 by radical oxidation (FIG. 13(d)). The silicon oxide film 14 is formed on the first p-type semiconductor region 10a. The silicon oxide film 14 is formed on the second p-type semiconductor region 10b.

[0175] The semiconductor layer 10 is oxidized by radical oxidation to form a silicon oxide film 14. The silicon oxide film 14 is an example of a second film.

[0176] The silicon oxide film 14 on the first p-type semiconductor region 10a will eventually become the first lower film 101a, and the silicon oxide film 14 on the second p-type semiconductor region 10b will eventually become the second lower film 201a.

[0177] A second thickness (d2 in FIG. 13(d)) of the silicon oxide film 14 between the first p-type semiconductor region 10a and the aluminum oxide film 12 is thicker than the first thickness d1 of the aluminum oxide film 12. A third thickness (d3 in FIG. 13(d)) of the silicon oxide film 14 on the second p-type semiconductor region 10b is thinner than the second thickness d2 of the silicon oxide film 14.

[0178] Due to the enhanced oxidation, the silicon oxide film 14 on the first p-type semiconductor region 10a becomes thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0179] The degree of the enhanced oxidation varies depending on the thickness of the first film formed on the semiconductor layer 10. For example, when the first film becomes thicker than a predetermined thickness, the enhanced oxidation is suppressed. In this case, the predetermined thickness is, for example, 5 nm. Also, when the first film becomes thinner than a predetermined thickness, the enhanced oxidation is suppressed. In this case, the predetermined thickness is, for example, 1 nm.

[0180] According to the method for manufacturing a semiconductor device of the sixth embodiment, the aluminum oxide film 12 on the second p-type semiconductor region 10b is made thicker than the aluminum oxide film 12 on the first p-type semiconductor region 10a, thereby suppressing the accelerated oxidation. Therefore, the silicon oxide film 14 on the first p-type semiconductor region 10a is thicker than the silicon oxide film 14 on the second p-type semiconductor region 10b.

[0181] Thereafter, the first gate electrode 102, the second gate electrode 202, and the n-type semiconductor region 10x are formed using a known process technology, thereby completing the manufacture of the semiconductor device shown in FIG.

[0182] As described above, according to the method for manufacturing a semiconductor device of the sixth embodiment, it is possible to oxidize a semiconductor layer at a low temperature and form oxide films with different thicknesses on the semiconductor layer.

[0183] In the third to sixth embodiments, the case where gate insulating layers of different thicknesses are formed has been described as an example. However, the semiconductor device manufacturing method of the present invention can also be applied to other cases where oxide films of different thicknesses are formed on the same semiconductor layer, such as when capacitor insulating layers of different thicknesses are formed.

[0184] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or changed with components of another embodiment. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0185] 10 Semiconductor layer 10a: First p-type semiconductor region (first region) 10b Second p-type semiconductor region (second region) 12 Aluminum oxide film (first film) 14 Silicon oxide film (second film) 16 Silicon oxynitride film (third film) 18 Hafnium oxide film (fourth film) 102 First gate electrode 202 Second gate electrode d1 First thickness d2 Second thickness d3 Third thickness d4 Fourth thickness

Claims

1. forming a first film containing a metal element and oxygen (O) and having a first thickness on a semiconductor layer containing silicon (Si); A method for manufacturing a semiconductor device, comprising: forming a second film, which contains silicon (Si) and oxygen (O) and has a second thickness that is thicker than the first thickness, between the semiconductor layer and the first film using radical oxidation.

2. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the first thickness is 1 nm or more and 5 nm or less.

3. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the second thickness is at least ten times the first thickness.

4. 2. The method of claim 1, wherein the temperature of the radical oxidation is 300.degree. C. or more and 900.degree. C. or less.

5. 2. The method for manufacturing a semiconductor device according to claim 1, further comprising forming a third film containing silicon (Si), oxygen (O), and nitrogen (N) on the semiconductor layer before forming the first film on the semiconductor layer.

6. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the first film contains at least one element selected from the group consisting of nitrogen (N), carbon (C), hydrogen (H), fluorine (F), and chlorine (Cl).

7. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the radical oxidation atmosphere contains hydrogen (H) and oxygen (O), and the atomic ratio of hydrogen (H) to the sum of hydrogen (H) and oxygen (O) (H / (H+O)) is 40% or less.

8. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the radical oxidation atmosphere contains hydrogen (H) and oxygen (O), and the atomic ratio of hydrogen (H) to the sum of hydrogen (H) and oxygen (O) (H / (H+O)) is 2% or more and 5% or less.

9. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the metal element is at least one metal element selected from the group consisting of aluminum (Al), hafnium (Hf), zirconium (Zr), lanthanum (La), yttrium (Y), titanium (Ti), nickel (Ni), zinc (Zn), indium (In), tin (Sn), gallium (Ga), and tungsten (W).

10. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor layer is a single crystal silicon layer or a polycrystalline silicon layer.

11. forming a first film containing a first metal element and oxygen (O) and having a first thickness on at least the first region of a semiconductor layer containing silicon (Si) and including a first region and a second region; A method for manufacturing a semiconductor device, comprising: forming, using radical oxidation, a second film between the first region and the first film and on the second region, the second film including silicon (Si) and oxygen (O), the second thickness on the first region being thicker than the first thickness, and the third thickness on the second region being thinner than the second thickness.

12. 12. The method for manufacturing a semiconductor device according to claim 11, wherein the first film is selectively formed on the first region.

13. 12. The method for manufacturing a semiconductor device according to claim 11, further comprising forming a third film containing silicon (Si), oxygen (O), and nitrogen (N) on the first region before forming the first film.

14. forming a fourth film having a fourth thickness on the second region, the fourth film including a second metal element different from the first metal element and oxygen (O) before forming the first film or after forming the first film and before forming the second film; The method for manufacturing a semiconductor device according to claim 11 , wherein the third thickness is greater than the fourth thickness.

15. 12. The method of claim 11, wherein a thickness of the first film on the second region is different from a thickness of the first film on the first region.

16. forming a first gate electrode above the second film in the first region; 12. The method for manufacturing a semiconductor device according to claim 11, further comprising forming a second gate electrode above the second film in the second region.

17. 12. The method for manufacturing a semiconductor device according to claim 11, wherein the first thickness is not less than 1 nm and not more than 5 nm.

18. 12. The method for manufacturing a semiconductor device according to claim 11, wherein the first metal element is at least one metal element selected from the group consisting of aluminum (Al), hafnium (Hf), zirconium (Zr), lanthanum (La), yttrium (Y), titanium (Ti), nickel (Ni), zinc (Zn), indium (In), tin (Sn), gallium (Ga), and tungsten (W).

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