Laminated structure

Abstract

This laminated structure (10) has: a substrate (11) including a principal surface (11p); and a buffer film (12) formed on the principal surface (11p). The substrate (11) is composed of a Si(100) substrate or a SOI substrate including a SOI layer formed of a Si(100) film. The buffer film (12) includes a first portion (PR1) and a second portion (PR2) different from the first portion (PR1). The first portion (PR1) is composed of a first metal oxide containing at least one metal element selected from the group consisting of group 4 elements other than Hf, and the second portion (PR2) is composed of a second metal oxide containing Hf. One among the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, and the other has a tetragonal crystal structure and is (001) oriented.

Description

Laminated structure

[0001] This invention relates to a laminated structure.

[0002] A film structure comprising a substrate, a conductive film formed on the substrate, and a piezoelectric film formed on the conductive film is known, specifically a laminated structure comprising a substrate, a platinum-containing conductive film formed on the substrate, and a lead zirconate titanate (PZT)-containing piezoelectric film formed on the conductive film. In such a laminated structure, the orientation direction of the piezoelectric film formed on the conductive film can be controlled by controlling the orientation direction of the platinum-containing conductive film. Furthermore, a technique is known in which a conductive film is formed on a general-purpose silicon (Si) substrate via a special buffer film in order to control the orientation of the platinum-containing conductive film.

[0003] Japanese Patent Publication No. 6498821 (Patent Document 1) discloses a technology for a film structure comprising: a silicon substrate including a main surface consisting of (100) planes; a first film formed on the main surface, having a cubic crystal structure and including a (100) oriented first zirconium oxide film; and a conductive film formed on the first film, having a cubic crystal structure and including a (100) oriented platinum film. In the technology described in Patent Document 1, the first film includes a film portion formed on the main surface and a plurality of protrusions each protruding from the upper surface of the film portion, and the cross-sectional shape of the protrusions perpendicular to the first direction along the main surface is triangular.

[0004] International Publication No. 2022 / 168800 (Patent Document 2) discloses a laminated structure comprising a substrate and an interlayer formed on the substrate, wherein the interlayer contains a metal oxide with Hf as an essential element and has a columnar or plate-like crystalline structure, and the interlayer satisfies at least the following conditions (1) or (2): (1) the metal oxide contains, in addition to Hf, one or more further metal elements selected from Group 4 elements, and (2) the interlayer further contains oxides of amphoteric elements and / or rare earth elements. In the technique described in Patent Document 2, the metal oxide contains Hf and Zr, and the interlayer has a plurality of protrusions on the upper surface of the columnar or plate-like crystalline structure.

[0005] Japanese Patent No. 6498821, International Publication No. 2022 / 168800

[0006] The Chemical Society of Japan (ed.), "Basic Chemical Handbook," 5th revised edition, Maruzen Publishing Co., Ltd., February 2004, p. II-291.

[0007] In the technology described in Patent Document 1 above, zirconium oxide (ZrO) having a cubic crystal structure and (100) orientation is placed on a Si(100) substrate. ２ A conductive film made of platinum (Pt) is formed via a buffer film made of ). In addition, in the technology described in Patent Document 2 above, a conductive film made of hafnium oxide (HfO) is formed on a Si substrate. ２ A conductive film made of Pt is formed via an interlayer (buffer film) containing ).

[0008] However, ZrO ２ and HfO ２ In its bulk state, Pt has a monoclinic, tetragonal, or cubic crystal structure. Therefore, when depositing a buffer film in a vacuum deposition apparatus, the crystal structure changes depending on the deposition conditions, making it difficult to stably deposit buffer films with the same crystal structure. Furthermore, the orientation direction and film quality of a conductive film made of Pt depend on the crystal structure, orientation direction, and film quality of the buffer film. Therefore, if it is not possible to stably deposit a buffer film with the same crystal structure, it is difficult to stably deposit a conductive film with the same orientation direction and film quality on the buffer film.

[0009] The present invention aims to provide a laminated structure having a buffer film deposited on a Si substrate, which can stably deposit buffer films having the same crystal structure and can stably deposit conductive films having the same orientation direction and film quality on the buffer films.

[0010] As a result of diligent research, the inventors have found that the above problem can be solved by the following configuration. [1] A laminated structure comprising: a substrate including a main surface; and a first film formed on the main surface, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate comprising: a substrate made of a Si substrate; an insulating layer on the substrate; and an SOI layer made of a Si(100) film on the insulating layer which includes the main surface which is made of a Si(100) plane, wherein the first film comprises: a first portion; and a second portion different from the first portion, wherein the first portion is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf; and the second portion is made of a second metal oxide containing Hf, wherein one of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, and the other of the first metal oxide and the second metal oxide has a tetragonal crystal structure and is (001) oriented. [2] The laminated structure according to [1], wherein the first portion comprises a first metal oxide comprising one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and one or more metal elements selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and Group 2 elements, wherein the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented. [3] A laminated structure according to [1], wherein the first film includes a third portion which is different from both the first portion and the second portion, the third portion is made of a third metal oxide containing Hf, the first metal oxide has a cubic crystal structure and is (100) oriented, the second metal oxide has a tetragonal crystal structure and is (001) oriented, and the third metal oxide has a monoclinic crystal structure and is (100) oriented or (001) oriented. [4] A laminated structure according to [1], wherein the first portion is made of the first metal oxide represented by the following composition formula (1): (Hf １－ｘ１ Zr ｘ１ ) O ２... (1) wherein x1 satisfies 0 < x1 ≦ 1, and the second part is composed of the second metal oxide represented by the following compositional formula (2), (Hf １－ｘ２ Zr ｘ２ )O ２... (2) A laminated structure in which x2 satisfies 0 ≤ x2 < 1, and x1 and x2 satisfy x2 < x1. [5] A laminated structure in which the first film comprises a film portion formed on the main surface and a plurality of pyramidal portions each protruding from the upper surface of the film portion, each of the film portion and the plurality of pyramidal portions comprises the first portion or the second portion, and the angle between the side of each of the plurality of pyramidal portions and the main surface is 40 to 50° when viewed from the <100> direction along the main surface of the Si(100) substrate or from the <100> direction along the main surface of the SOI layer. [6] A laminated structure in which the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented. [7] A laminated structure according to [6], wherein the first metal oxide is oriented such that the <100> direction along the main surface of the first metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer, and the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer. [8] A laminated structure according to [4], wherein the first metal oxide has a tetragonal crystal structure and is (001) oriented, and the second metal oxide has a cubic crystal structure and is (100) oriented. [9] A laminated structure according to [8], wherein the first metal oxide is oriented such that the <100> direction along the main surface of the first metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer, and the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer.

[10] In the laminated structure described in any of [6] to [9], the first metal oxide is ZrO. ２ The second metal oxide is HfO ２ A laminated structure, wherein

[11] [2], the first part consists of the first metal oxide represented by the following composition formula (3), (Hf １－ｘ１－ｙ１ Zr ｘ１ M ｙ１ ) O ２－ｚ１ ... (3) (However, in composition formula (6), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) The y1 satisfies 0 < y1 ≤ 0.3, the x1 satisfies 0 < x1 ≤ 1 - y1, and the second part consists of the second metal oxide represented by the following composition formula (4): (Hf １－ｘ２－ｙ２ Zr ｘ２ M ｙ２ ) O ２－ｚ２ ... (4) (However, in composition formula (4), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al and group 2 elements.) The y2 satisfies 0 ≤ y2 < 0.3, the x2 satisfies 0 ≤ x2 ≤ 1 - y2, the y1 and y2 satisfy y2 < y1, the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented, a laminated structure.

[12] In the laminated structure described in

[11] , the second portion is adjacent to the first portion in a first direction along the main surface, the first film includes a third portion that is positioned on the opposite side of the first portion with the second portion in between in the first direction and is adjacent to the first portion, the third portion consists of a third metal oxide represented by the following composition formula (5): (Hf １－ｘ３－ｙ３ Zr ｘ３ M ｙ３ ) O ２－ｚ３... (5) (However, in composition formula (5), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al and group 2 elements.) The y3 satisfies 0 < y3 ≤ 0.3, the x3 satisfies 0 < x3 ≤ 1 - y3, the y2 and y3 satisfy y3 > y2, and the third metal oxide has a cubic crystal structure and is (100) oriented, a laminated structure.

[13] The laminated structure according to

[11] , wherein the second portion includes a film portion formed on the main surface and a pyramidal portion protruding from the upper surface of the film portion, and the angle between the side of the pyramidal portion and the main surface is 40 to 50° when viewed from the <100> direction along the main surface of the Si(100) substrate or from the <100> direction along the main surface of the SOI layer.

[14] In the laminated structure described in

[12] , the first film includes a fourth portion disposed between the first portion and the third portion in the first direction, and the fourth portion consists of a fourth metal oxide represented by the following composition formula (6): (Hf １－ｘ４－ｙ４ Zr ｘ４ M ｙ４ ) O ２－ｚ４... (6) (wherein in composition formula (6), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) The y4 satisfies 0 ≤ y4 < 0.3, the x4 satisfies 0 < x4 ≤ 1 - y4, the x2 and x4 satisfy x4 > x2, the y1 and y4 satisfy y4 < y1, the y3 and y4 satisfy y4 < y3, and the fourth metal oxide has a cubic crystal structure and is (100) oriented, a laminated structure.

[15] A laminated structure according to

[14] , wherein the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer, and the fourth metal oxide is oriented such that the <100> direction along the main surface of the fourth metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer.

[16] A laminated structure according to

[14] or

[15] , wherein the second metal oxide is HfO ２ The fourth metal oxide is ZrO ２ A laminated structure, wherein

[17] In the laminated structure described in

[12] , the first film includes a fifth portion disposed between the first portion and the third portion in the first direction, and the fifth portion consists of a fifth metal oxide represented by the following composition formula (7): (Hf １－ｘ５－ｙ５ Zr ｘ５ M ｙ５ ) O ２－ｚ５... (7) (wherein in composition formula (7), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) The y5 satisfies 0 < y5 < 0.3, the x5 satisfies 0 ≤ x5 ≤ 1 - y5, the x2 and x5 satisfies x5 < x2, the y1 and y5 satisfies y5 < y1, the y3 and y5 satisfies y5 < y3, and the fifth metal oxide has a cubic crystal structure and is (100) oriented, a laminated structure.

[18] A laminated structure according to

[17] , wherein the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer, and the fifth metal oxide is oriented such that the <100> direction along the main surface of the fifth metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer.

[19] A laminated structure according to

[17] or

[18] , wherein the second metal oxide is ZrO ２ The fifth metal oxide is HfO ２ A laminated structure, wherein

[20] [3], the first part consists of the first metal oxide represented by the following composition formula (8), (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (8) The x1 satisfies 0 < x1 ≤ 1, and the second part consists of the second metal oxide represented by the following composition formula (9), (Hf １－ｘ２ Zr ｘ２ ) O ２ ... (9) The x2 satisfies 0 < x2 < 1, and the third part consists of the third metal oxide represented by the following composition formula (10), (Hf １－ｘ３ Zr ｘ３ ) O ２... (10) A laminated structure in which x3 satisfies 0 ≤ x3 < 1, and x1, x2 and x3 satisfy x3 < x2 < x1.

[21] A laminated structure in which the first metal oxide is oriented such that the <100> direction along the main surface of the first metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer, and the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer.

[22] A laminated structure in which the first metal oxide is ZrO ２ The third metal oxide is HfO ２A laminated structure, wherein:

[23] A laminated structure comprising: a substrate including a main surface; and a first film formed on the main surface, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate comprising: a substrate made of a Si substrate; an insulating layer on the substrate; and an SOI layer made of a Si(100) film on the insulating layer which includes the main surface which is made of a Si(100) plane, wherein the first film comprises: a first portion; and a second portion different from the first portion, wherein the first portion is made of a first metal oxide comprising one or more metal elements selected from the group consisting of Group 4 elements other than Hf; the second portion is made of a second metal oxide comprising Hf; the first metal oxide has a tetragonal crystal structure and is (001) oriented; and the second metal oxide has a monoclinic crystal structure and is (100) oriented.

[24] A laminated structure comprising a substrate including a main surface and a first film formed on the main surface, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate comprising a substrate made of a Si substrate, an insulating layer on the substrate, and an SOI layer which is made of a Si(100) film on the insulating layer and includes the main surface which is made of a Si(100) plane, the first film is made of a first metal oxide comprising Hf and one or more metal elements selected from group 4 elements other than Hf, the first metal oxide has a tetragonal crystal structure and is (001) oriented, the laminated structure.

[25] In the laminated structure according to

[24] , the first film is made of the first metal oxide represented by the following composition formula (11): (Hf １－ｘ１ Zr ｘ１ ) O ２... (11) A laminated structure in which x1 satisfies 0 ≤ x1 < 1.

[26] A laminated structure in which the first film comprises a film portion formed on the main surface and a plurality of pyramidal portions each protruding from the upper surface of the film portion, wherein each of the film portion and the plurality of pyramidal portions is made of the first metal oxide, and the angle between each of the sides of the plurality of pyramidal portions and the main surface is 50 to 60° when viewed from the <100> direction along the main surface of the Si(100) substrate or from the <100> direction along the main surface of the SOI layer.

[27] A laminated structure in which the x1 satisfies 0.25 ≤ x1 < 1 ≤ 0.98, and the lattice constant c of the first metal oxide having a tetragonal crystal structure is 0.516 to 0.519 nm.

[28] A laminated structure comprising: a substrate including a main surface; a first film formed on the main surface; and a second film formed on the first film, wherein the substrate is a Si substrate, or an SOI substrate comprising a substrate made of a Si substrate, an insulating layer on the substrate, and an SOI layer on the insulating layer; the first film is made of a first metal compound comprising Hf and one or more metal elements selected from group 4 elements other than Hf; the second film is made of a second metal compound comprising one or more metal elements selected from group 2 elements; the first film comprises: a film portion formed on the main surface; and a plurality of adjacent peaks protruding from the upper surface of the film portion; a valley portion is formed between two adjacent peaks among the plurality of peaks; a metal portion made of a platinum group element is formed in the valley portion; and the second film is formed on the first film so as to cover the side portions of each of the plurality of peaks and the metal portion formed in the valley portion. A laminated structure in which the tips of the multiple peaks are in direct contact with the second film without the metal portion in between.

[29] A laminated structure according to

[28] , wherein the metal portion is formed in the deepest part of the valley, the second film is formed on the first film so as to cover the metal portion formed in the deepest part of the valley, the first height which is the height of each of the plurality of peaks is 5 to 30 nm, the ratio of the thickness of the metal portion to the first height is 0.2 or less, the metal portion has a cubic crystal structure and is (111) oriented, and the second film has a cubic crystal structure and is (111) oriented.

[30] A laminated structure according to

[28] , wherein the first height which is the height of each of the plurality of peaks is 5 to 30 nm, the ratio of the thickness of the metal portion to the first height is 0.25 to 0.75, and the second film has a cubic crystal structure and is (110) oriented.

[31] In the laminated structure described in

[28] , the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate including a base body made of a Si substrate, an insulating layer on the base body, and an SOI layer on the insulating layer which is made of a Si(100) film and includes the main surface which is made of a Si(100) plane, the first height which is the height of each of the plurality of peaks is 5 to 30 nm, the ratio of the thickness of the metal part to the first height is 0.8 to 0.95, the first metal compound has a cubic crystal structure and is (100) oriented, or has a tetragonal crystal structure and is (001) oriented, the metal part has a cubic crystal structure and is (100) oriented, and the second film has a cubic crystal structure and is (100) oriented, in a laminated structure.

[32] A laminated structure according to any of [2] to [9], any of

[11] to

[15] ,

[17] or

[18] ,

[20] or

[21] , or

[23] , comprising: a conductive film formed on the first film; and a piezoelectric film formed on the conductive film, wherein the conductive film has a cubic crystal structure and is made of a (100) oriented metal; the piezoelectric film is made of a sixth metal oxide that is (100) oriented in pseudocubic crystal representation; and the first metal oxide or the second metal oxide is twinned or slip deformed such that the first lattice constant along the main surface of the first metal oxide or the second metal oxide approaches the second lattice constant along the main surface of the sixth metal oxide.

[33] A laminated structure according to any one of

[24] to

[26] , comprising: a conductive film formed on the first film; and a piezoelectric film formed on the conductive film, wherein the conductive film has a cubic crystal structure and is made of a (100) oriented metal; the piezoelectric film is made of a second metal oxide that is (100) oriented in pseudocubic crystal representation; and the first metal oxide is twinned or slip deformed such that the first lattice constant along the main surface of the first metal oxide approaches the second lattice constant along the main surface of the second metal oxide.

[0011] The laminated structure of the present invention is a laminated structure having a buffer film deposited on a Si substrate, and it is possible to stably deposit a buffer film having the same crystal structure, and to stably deposit a conductive film having the same orientation direction and film quality on the buffer film.

[0012] This is a cross-sectional view showing an example of the laminated structure of Embodiment 1. This is a cross-sectional view showing another example of the laminated structure of Embodiment 1. This is a diagram showing a fluorite-type structure. This is a diagram for explaining twinning deformation. This is a diagram for explaining slip deformation. This is a diagram showing an example of the first and second parts in the laminated structure of Embodiment 1. This is a diagram showing an example of the first and second parts in the laminated structure of Embodiment 1. YSZ, ZrO ２ and HfO ２This is a diagram schematically showing the relationship between the film deposition temperature and the crystal structure. This is a diagram showing the relationship between the film deposition temperature and the observed peaks. This is a cross-sectional view showing another example of the laminated structure of Embodiment 1. This is a cross-sectional view showing an example of the laminated structure of the first modified example of Embodiment 1. This is a diagram showing an example of the second part of the laminated structure of the first modified example of Embodiment 1. This is a cross-sectional view showing an example of the laminated structure of the second modified example of Embodiment 1. This is a cross-sectional view showing an example of the laminated structure of the third modified example of Embodiment 1. This is a cross-sectional view showing an example of the laminated structure of Embodiment 2. This is a diagram showing an example of the first and second parts of the laminated structure of Embodiment 2. This is a diagram showing an example of the first and second parts of the laminated structure of Embodiment 2. This is a cross-sectional view showing an example of the laminated structure of Embodiment 3. This is a cross-sectional view showing another example of the laminated structure of Embodiment 3. This is a cross-sectional view showing another example of the laminated structure of Embodiment 3. This is a cross-sectional view showing an example of the laminated structure of the first modified example of Embodiment 3. This is a cross-sectional view showing an example of the laminated structure of the second modified example of Embodiment 3. This is a graph showing the diffraction pattern of the laminated structure of Embodiment 1. This is a graph showing the φ scan of the laminated structure of Embodiment 1. This is a graph showing the diffraction pattern of the laminated structure of Embodiment 1. This is a multi-wave interference image of the laminated structure of Embodiment 1. This is the electron diffraction pattern of the laminated structure of Example 1. This is a graph showing the diffraction pattern of the laminated structure of Example 2. This is a graph showing the φ scan of the laminated structure of Example 2. This is the STEM image and compositional analysis results of the laminated structure of Example 2. This is a graph showing the diffraction pattern of the laminated structure of Example 3. This is a graph showing the diffraction pattern of the laminated structure of Example 4. This is a graph showing the diffraction pattern of the laminated structure of Example 5. This is a graph showing the diffraction pattern of the laminated structure of Example 6. This is a graph showing the φ scan of the laminated structure of Example 6. This is a graph showing the Zr / Hf ratio dependence of the calculated c-axis length for the laminated structure of Example 7. This is a graph showing the diffraction pattern of the laminated structure of Example 8. This is a graph showing the diffraction pattern of the laminated structure of Example 9. This is a graph showing the diffraction pattern of the laminated structure of Example 10. This is a graph showing the diffraction pattern of the laminated structure of Example 11. This is a graph showing the diffraction pattern of the laminated structure of Example 11. This is the STEM image of the laminated structure of Example 11.This is a STEM image of the stacked structure of Example 11. This is a STEM grid image of the HZO contained in the buffer film of the stacked structure of Example 11. This is a STEM grid image of the HZO contained in the buffer film of the stacked structure of Example 11.

[0013] The embodiments of the present invention will be described below with reference to the drawings.

[0014] Furthermore, the disclosure is merely an example, and any modifications that a person skilled in the art could easily conceive while maintaining the spirit of the invention are naturally included within the scope of the present invention. In addition, the drawings may schematically represent the width, thickness, shape, etc. of each part in order to clarify the explanation, but these are merely examples and do not limit the interpretation of the present invention.

[0015] (Embodiment 1) <Laminated Structure> First, the laminated structure of Embodiment 1 will be described. Figure 1 is a cross-sectional view showing an example of the laminated structure of Embodiment 1. Figure 2 is a cross-sectional view showing another example of the laminated structure of Embodiment 1. Figure 3 is a diagram showing a fluorite-type structure. Figure 4 is a diagram for explaining twinning deformation, and Figure 5 is a diagram for explaining slip deformation. The left side of each of Figures 3 and 4 shows the atomic arrangement of metal atoms AT1 before deformation, and the right side of each of Figures 3 and 4 shows the atomic arrangement of metal atoms AT1 after deformation. Figures 6 and 7 are diagrams showing examples of the first and second parts in the laminated structure of Embodiment 1. In Figure 6, for ease of understanding, ZrO ２ or HfO ２ In the crystal lattices shown, the oxygen (O) atoms are omitted from the illustration, and only the metal atoms of Zr and Hf are depicted.

[0016] Figure 8 shows YSZ, ZrO ２ and HfO ２ This figure schematically shows the relationship between the film deposition temperature and the crystal structure. Figure 9 shows the relationship between the film deposition temperature and the observed peaks. Figure 10 is a cross-sectional view showing another example of the laminated structure of Embodiment 1.

[0017] The laminated structure 10 shown in Figure 1 comprises a substrate 11 including a main surface 11p, and a buffer film (first film) 12 formed on the main surface 11p. In Figure 8, the laminated structure 10 of Embodiment 1 is denoted as laminated structure 10a, the laminated structure of the first modified example of Embodiment 1 described later is denoted as laminated structure 10b, and the laminated structure 10 of Embodiment 2 described later is denoted as laminated structure 10c.

[0018] In the example shown in Figure 1, the substrate 11 is made of a silicon (Si) (100) substrate including a main surface 11p made of a Si (100) surface. Alternatively, in the example shown in Figure 2, the substrate 11 is made of an SOI (Silicon On Insulator) substrate including a base body 11a made of a Si substrate, an insulating layer 11b on the base body 11a, and an SOI (Silicon On Insulator) layer 11c on the insulating layer 11b that is made of a Si (100) film and includes a main surface 11p made of a Si (100) surface.

[0019] The buffer film 12 includes a first portion PR1 and a second portion PR2 that is different from the first portion PR1. The first portion PR1 is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf. The second portion PR2 is made of a second metal oxide containing Hf.

[0020] One of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, while the other of the first and second metal oxides has a tetragonal crystal structure and is (001) oriented.

[0021] In the examples shown in Figures 1, 2, and 6, the first portion PR1 is a ZrO having a cubic crystal structure and (100) orientation. ２ The following is an example of a part consisting of a tetragonal crystal structure and (001)-oriented HfO ２ The following are examples of the resulting parts. Note that for the first part PR1 and the second part PR2, it is sufficient that the Zr / Hf ratio and crystal structure differ between the first part PR1 and the second part PR2. Therefore, the example shown in Figure 6 illustrates possible examples for the first part PR1 and the second part PR2 for ease of understanding, and the structures of the first part PR1 and the second part PR2 are not particularly limited.

[0022] Furthermore, as will be explained later using Figure 23, the buffer film 12 includes a first portion PR1 and a second portion PR2, and in the diffraction pattern obtained by X-ray diffraction measurement using the θ-2θ method, ZrO has a cubic crystal structure. ２ or HfO ２ Diffraction peaks of the (200) plane (HZO c(002)), etc., and ZrO having a tetragonal structure. ２ or HfO ２ This can be confirmed by observing diffraction peaks (HZO t(002)) on the (002) plane, etc. (the same applies to the first, second, and third modifications of Embodiment 1, and Embodiment 2, which will be described later).

[0023] In the technology described in Patent Document 1 above, a cubic crystal structure and (100)-oriented ZrO are placed on a Si(100) substrate. ２ A conductive film made of Pt is formed via a buffer film made of . In addition, in the technology described in Patent Document 2 above, an HfO ２ A conductive film made of Pt is formed via an interlayer containing [a specific material].

[0024] However, ZrO ２ and HfO ２ In its bulk state, Pt has a monoclinic, tetragonal, or cubic crystal structure. Therefore, when depositing a buffer film in a vacuum deposition apparatus, the crystal structure fluctuates depending on the deposition conditions, making it difficult to stably deposit buffer films with the same crystal structure. Furthermore, the orientation direction and film quality of a conductive film made of Pt depend on the crystal structure, orientation direction, and film quality of the buffer film. Therefore, if it is not possible to stably deposit a buffer film with the same crystal structure, it is difficult to stably deposit a conductive film with the same orientation direction and film quality on the buffer film.

[0025] On the other hand, in the laminated structure of this embodiment 1, the buffer film 12 includes a first portion PR1 and a second portion PR2 that is different from the first portion PR1. The first portion PR1 is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and the second portion PR2 is made of a second metal oxide containing Hf. Furthermore, one of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, and the other of the first metal oxide and the second metal oxide has a tetragonal crystal structure and is (001) oriented. That is, the inventors have found that the buffer film 12 consists of two types of portions, each having a different Zr / Hf ratio and a different crystal structure.

[0026] In such cases, a conductive film 13, a conductive film 14, and a piezoelectric film 15, which will be described later using Figure 10, can be easily epitaxially grown on a substrate 11 made of a Si substrate or an SOI substrate, via a buffer film 12 including a first portion PR1 and a second portion PR2. This is because, for example, the main component of the first portion PR1 and the second portion PR2 is HfO ２ or ZrO ２ It is believed that the dynamic lattice matching effect due to the twinning martensitic transformation exhibited by the first and second metal oxides acts as the driving force, propulsion, and propulsion during the epitaxial growth of the conductive film 13, conductive film 14, and piezoelectric film 15, according to the crystal growth mechanism.

[0027] Furthermore, according to the laminated structure of this embodiment 1, by adjusting the temperature and pressure conditions when depositing the buffer film 12, one portion of the structure with a large Zr / Hf ratio and the other portion with a small Zr / Hf ratio can have a cubic crystal structure, while the other portion has a tetragonal crystal structure. Therefore, even when depositing the buffer film in a vacuum deposition apparatus, it is possible to prevent or suppress fluctuations in the crystal structure due to temperature conditions during film deposition, and to stably deposit a buffer film 12 having the same crystal structure. Also, when depositing a conductive film made of Pt on the buffer film 12, it is possible to stably deposit a conductive film having the same orientation direction and film quality.

[0028] Furthermore, if either the first portion PR1 or the second portion PR2 has a cubic crystal structure and the other has a tetragonal crystal structure, even when the conductive film and piezoelectric film on the buffer film 12 are made of a wide range of materials, a dynamic lattice matching effect due to twinning martensitic transformation can be ensured depending on the material, and high-quality conductive films and piezoelectric films can be formed.

[0029] As shown in Figure 3, HfO ２ and ZrO ２ Furthermore, the HZO represented by compositional formulas (1) and (2) described later is an oxide that has a fluorite structure, undergoes martensitic transformation, and grows epitaxially on a Si substrate. Also, as shown in Figures 4 and 5, typical martensitic transformations include twinning and sliding deformation. On the other hand, as will be explained using Figure 45 in Example 11 described later, it was found that the buffer film 12 underwent martensitic transformation accompanied by twinning. Therefore, as described above, the fact that a conductive film 13 etc. can be easily epitaxially grown on the substrate 11 via the buffer film 12 is due to the HfO contained in the buffer film 12. ２ , ZrO ２ Alternatively, this is thought to be due to the HZO undergoing martensitic transformation (the same applies to the first, second, and third modifications of Embodiment 1 described later, as well as Embodiment 2).

[0030] Preferably, the first portion PR1 consists of a first metal oxide represented by the following compositional formula (1), and the second portion PR2 consists of a second metal oxide represented by the following compositional formula (2). (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (1) (Hf １－ｘ２ Zr ｘ２ ) O ２ ... (2) In the above composition formula (1) and composition formula (2), x1 satisfies 0 < x1 ≤ 1, x2 satisfies 0 ≤ x2 < 1, and x1 and x2 satisfy x2 < x1.

[0031] In the following, among the first metal oxides represented by the above compositional formula (1), the case where 0 < x1 < 1 may be referred to as HZO (the same applies to x2 in the above compositional formula (2)). In that case, the first part PR1 is ZrO ２ or consists of HZO, and the second part PR2 is HZO or HfO ２ It consists of and the Zr / Hf ratio in the first part PR1 is greater than the Zr / Hf ratio in the second part PR2. Therefore, as mentioned above, one of the parts with a large Zr / Hf ratio and the part with a small Zr / Hf ratio can have a cubic crystal structure, and the other can have a tetragonal crystal structure. Also, as mentioned above, "ZrO ２ or HfO ２ "(200) planes" is "ZrO ２ , HZO or HfO ２ It means "(200) faces, etc."

[0032] If both the first and second metal oxides are HZO, then both the first and second metal oxides are HfO ２ Although a portion of the Hf is replaced with Zr, Zr is a group 4 element and a period 5 element, and Hf is a group 4 element and a period 6 element, so their chemical properties are similar, and it is possible to prevent or suppress fluctuations in its crystal structure depending on the temperature conditions when the buffer film 12 is formed.

[0033] As shown in Figures 1 and 2, preferably, the buffer membrane 12 includes a membrane portion 12a formed on the main surface 11p and a plurality of pyramidal portions 12b each protruding from the upper surface of the membrane portion 12a. Each of the membrane portion 12a and the plurality of pyramidal portions 12b includes a first portion PR1 or a second portion PR2.

[0034] For example, if the buffer film 12 has a cubic crystal structure and is (100) oriented, or has a tetragonal crystal structure and is (001) oriented, the side surface of the pyramidal portion 12b will be, for example, a (111) plane, and will not be a (100) plane in the cubic representation of HZO. Therefore, the (111) plane of a metal film made of, for example, Pt (conductive film 13, which will be explained later using Figure 10) is more likely to grow on the side surface of the pyramidal portion 12b, making it easier for the metal film on the buffer film 12 to be (100) oriented in the cubic representation, and making it easier for a single-crystal metal film to be formed.

[0035] As shown in Figures 1 and 2, the entire pyramidal portion 12b may be the first portion PR1, the entire pyramidal portion 12b may be the second portion PR2, or the pyramidal portion 12b may include both the first portion PR1 and the second portion PR2.

[0036] As shown in Figures 1 and 2, preferably, when viewed from the <100> direction (Si<100> direction) along the main surface 11p of the Si(100) substrate, or from the <100> direction along the main surface 11p of the SOI layer, the angle a1 between each side SD1 of the multiple pyramidal portions 12b and the main surface 11p is 40 to 50°, and more preferably approximately 45°.

[0037] In the examples shown in Figures 6 and 7, the first portion PR1 has a cubic crystal structure and ZrO ２ In the unit cell UC1, which consists of two face-centered cubic lattices, four of the eight Zr atoms are replaced by Hf, resulting in a tetragonal crystal structure and HfO ２ A unit cell UC2, which is a single body-centered tetragonal lattice, is generated. In such an example, the angle b1 between the edge line RD1 connecting the two Hf elements in the unit cell UC2, one located at the body center and the other at a position other than the body center, and the upper surface of the unit cell UC2 is approximately 45°. Therefore, when viewed from the <100> direction (Si<100> direction) along the main surface 11p of the Si(100) substrate, the angle a1 between the side edge SD1 of the pyramidal portion 12b and the main surface 11p is approximately 45°. One possible reason for the formation of the pyramidal portion 12b is that slip deformation occurs along the edge line RD1.

[0038] Preferably, the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented. Also preferably, the first metal oxide is oriented such that the <100> direction along the main surface 11p of the first metal oxide is parallel to the <100> direction along the main surface 11p of the Si(100) substrate (Si<100> direction), or to the <100> direction along the main surface 11p of the SOI layer. Also preferably, the second metal oxide is oriented such that the <100> direction along the main surface 11p of the second metal oxide is parallel to the <110> direction along the main surface 11p of the Si(100) substrate (Si<110> direction), or to the <110> direction along the main surface 11p of the SOI layer.

[0039] As shown in Figure 8, the inventors have found that the buffer film is HfO ２ In the case where the buffer film is ZrO, the temperature range in which a metal oxide with a monoclinic crystal structure is deposited, the temperature range in which a metal oxide with a tetragonal crystal structure is deposited, and the temperature range in which a metal oxide with a cubic crystal structure is deposited are such that the buffer film is ZrO ２ We found that, compared to the case where both conditions are met, they are both on the higher temperature side.

[0040] Therefore, when the buffer film 12 is formed in the temperature range RG1 shown in Figure 8, the first metal oxide having a Zr / Hf ratio greater than that of the second metal oxide can have a cubic crystal structure, and the second metal oxide having a Zr / Hf ratio smaller than that of the first metal oxide can have a tetragonal crystal structure.

[0041] In this way, because the buffer film 12 has two parts, a first part PR1 and a second part PR2, each having a different Zr / Hf ratio, it is possible to prevent or suppress fluctuations in its crystal structure due to temperature conditions during film formation, and to stably form a buffer film 12 with the same crystal structure.

[0042] Incidentally, as shown in FIG. 9, the inventors of the present invention found that in the diffraction pattern obtained by X-ray diffraction measurement using the θ-2θ method as the film formation temperature when forming the buffer film 12 decreases from high to low, ZrO ２ , HZO or HfO ２ of the diffraction peak (c(002)) of the (200) plane, ZrO having a tetragonal crystal structure ２ , HZO or HfO ２ of the diffraction peak (t(002)) of the (002) plane, ZrO having a monoclinic crystal structure ２ , HZO or HfO ２ of the diffraction peak (m(200)) of the (200) plane were sorted out to see which one was observed. In FIG. 9, when the buffer film 12 was formed in the temperature range RG1 shown in FIG. 8, it is indicated as "c(200) and t(200)".

[0043] Further, for example, in order for the conductor film 13 made of Pt and having a cubic crystal structure to be (100)-oriented on the buffer film 12, ZrO having a monoclinic crystal structure ２ , HZO or HfO ２ it is desirable that the diffraction peak (m(111)) of the (111) plane and the diffraction peak (m(11-1)) of the (11-1) plane are not observed. Therefore, the temperature range in which the conductor film 13 made of Pt and having a cubic crystal structure is (100)-oriented on the buffer film 12 is the temperature range indicated as "m(200)" and a temperature range higher than that.

[0044] Preferably, the first metal oxide is ZrO ２ and the second metal oxide is HfO ２ . In such a case, as shown in FIG. 8, since the difference in the Zr / Hf ratio between the first part PR1 and the second part PR2 can be increased, it is possible to prevent or suppress the crystal structure from fluctuating depending on the temperature conditions and the like when forming the buffer film 12, and it is possible to stably form the buffer film 12 having the same crystal structure.

[0045] Alternatively, preferably, the first metal oxide has a tetragonal crystal structure and is (001) oriented, and the second metal oxide has a cubic crystal structure and is (100) oriented. Also preferably, the first metal oxide is oriented such that the <100> direction along the main surface 11p of the first metal oxide is parallel to the <110> direction (Si<110> direction) along the main surface 11p of the Si(100) substrate, or to the <110> direction along the main surface 11p of the SOI layer. Also preferably, the second metal oxide is oriented such that the <100> direction along the main surface 11p of the second metal oxide is parallel to the <100> direction (Si<100> direction) along the main surface 11p of the Si(100) substrate, or to the <100> direction along the main surface 11p of the SOI layer.

[0046] As explained using Figure 8 above, when the buffer film 12 is formed in the temperature range RG1 shown in Figure 8, it is also possible that the first metal oxide having a Zr / Hf ratio greater than that of the second metal oxide has a cubic crystal structure, and the second metal oxide having a Zr / Hf ratio smaller than that of the first metal oxide has a tetragonal crystal structure.

[0047] However, by forming the buffer film 12 while increasing the temperature from a temperature range lower than the temperature range RG1 to the temperature range RG1, or by forming the buffer film 12 while decreasing the temperature from the temperature range RG1 to a temperature range lower than the temperature range RG1, the first metal oxide having a Zr / Hf ratio greater than that of the second metal oxide has a tetragonal crystal structure, and the second metal oxide having a Zr / Hf ratio smaller than that of the first metal oxide has a cubic crystal structure.

[0048] In such cases, the buffer film 12 has two parts, a first part PR1 and a second part PR2, each having a different Zr / Hf ratio. This prevents or suppresses fluctuations in the crystal structure of the buffer film 12 due to temperature conditions during deposition, allowing for the stable deposition of a buffer film 12 with the same crystal structure.

[0049] Furthermore, even when the first metal oxide has a tetragonal crystal structure and the second metal oxide has a cubic crystal structure, it is still represented as "c(200) and t(200)" in Figure 9.

[0050] Furthermore, even when the first metal oxide has a tetragonal crystal structure and the second metal oxide has a cubic crystal structure, preferably the first metal oxide is ZrO ２ The second metal oxide is HfO ２ In such cases, the difference in the Zr / Hf ratio between the first part PR1 and the second part PR2 can be increased, which prevents or suppresses fluctuations in the crystal structure of the buffer film 12 due to temperature conditions during film formation, and allows for the stable formation of a buffer film 12 having the same crystal structure.

[0051] As shown in Figure 10, preferably, the laminated structure 10 of this embodiment 1 comprises a conductive film 13 made of a platinum group element such as Pt formed on a buffer film 12, a conductive film 14 made of strontium ruthenate (SRO) formed on the conductive film 13, a piezoelectric film 15 made of lead zirconate titanate (PZT) formed on the conductive film 14, and a conductive film 16 formed on the piezoelectric film 15 (the same applies to the first, second, third, and second modifications of embodiment 1 described later). In such a case, by applying an electric field between the conductive film 14 and the conductive film 16, the laminated structure 10 can be operated as a piezoelectric actuator, for example.

[0052] As described above, according to this embodiment 1, a conductive film 13, a conductive film 14, and a piezoelectric film 15 can be easily epitaxially grown on a substrate 11 made of a Si substrate or an SOI substrate via a buffer film 12 including a first portion PR1 and a second portion PR2. This is because, for example, HfO is the main component of the first portion PR1 and the second portion PR2. ２ , HZO or ZrO ２It is thought that the dynamic lattice matching effect due to the twinning martensitic transformation exhibited by the first and second metal oxides acts as the driving force, propulsion, and propulsion during the epitaxial growth of the conductive film 13, conductive film 14, and piezoelectric film 15, according to the crystal growth mechanism. However, the theory is not necessarily limited to this.

[0053] Preferably, the conductive film 13 has a cubic crystal structure and is made of a metal, such as a platinum group element like Pt, which is (100) oriented, and the piezoelectric film 15 is made of a sixth metal oxide that is (100) oriented in a pseudocubic crystal representation. Furthermore, as will be explained later in Example 11 using Figure 45, the first or second metal oxide contained in the buffer film 12 undergoes twinning deformation or slip deformation such that the first lattice constant of the first or second metal oxide, which is along the main surface 11p of the substrate 11, approaches the second lattice constant of the sixth metal oxide contained in the piezoelectric film 15, which is along the main surface 11p of the substrate 11. In such cases, the dynamic lattice matching effect due to the twinning martensitic transformation exhibited by the first and second metal oxides acts as a driving force, propulsion, and propulsion force when the conductive film 13, conductive film 14, and piezoelectric film 15 undergo epitaxial growth. Therefore, the conductive film 13, conductive film 14, and piezoelectric film 15 can be easily epitaxially grown on a substrate 11 made of a Si substrate or an SOI substrate via a buffer film 12 containing the first portion PR1 and the second portion PR2 (the same applies to the first, second, and third modifications of Embodiment 1 described later).

[0054] <First Modified Example of Laminated Structure> Next, a first modified example of the laminated structure of Embodiment 1 will be described. The laminated structure of the first modified example of Embodiment 1 differs from the laminated structure of Embodiment 1 in that the first portion is made of, for example, partially stabilized HZO.

[0055] Figure 11 is a cross-sectional view showing an example of a laminated structure of the first modified embodiment of Embodiment 1. Figure 12 is a diagram showing an example of a second portion in the laminated structure of the first modified embodiment of Embodiment 1.

[0056] The laminated structure 10 shown in Figure 11, like the laminated structure 10 of Embodiment 1, has a substrate 11 made of a Si(100) substrate and including a main surface 11p, and a buffer film (first film) 12 formed on the main surface 11p. Alternatively, although not shown, the laminated structure 10 of this first modified example can also use a substrate 11 made of an SOI substrate as described above using Figure 2. The Si substrate is made of a Si(100) substrate, and the SOI layer is made of a Si(100) film.

[0057] In this first modified example, similar to the first embodiment, the buffer film 12 includes a first portion PR1 and a second portion PR2 that is different from the first portion PR1. The second portion PR2 consists of a second metal oxide containing Hf. The second metal oxide has a tetragonal crystal structure and is (001) oriented.

[0058] On the other hand, in this first modified example, unlike the first embodiment, the first portion PR1 consists of a first metal oxide comprising one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and one or more metal elements (M) selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and Group 2 elements. Furthermore, the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

[0059] In the examples shown in Figures 11 and 12, the first portion PR1 is exemplified as a portion consisting of YSZ having a cubic crystal structure and being (100) oriented, and the second portion PR2 is exemplified as a portion consisting of HZO having a tetragonal crystal structure and being (001) oriented. Note that for the first portion PR1 and the second portion PR2, it is sufficient that the composition and crystal structure differ between the first portion PR1 and the second portion. Therefore, the examples shown in Figures 11 and 12 illustrate possible examples for the first portion PR1 and the second portion PR2 for ease of understanding, and the structures of the first portion PR1 and the second portion PR2 are not particularly limited.

[0060] In the laminated structure of this first modified example, the buffer film 12 comprises a first portion PR1 and a second portion PR2 that is different from the first portion PR1. The first portion PR1 is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and one or more metal elements (M) selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and Group 2 elements. The second portion PR2 is made of a second metal oxide containing Hf. Furthermore, the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented. That is, the inventors have found that the buffer film 12 consists of two parts, each with a different composition and crystal structure.

[0061] In this case, similar to Embodiment 1, the conductive film 13, conductive film 14, and piezoelectric film 15, as described above using Figure 10, can be easily epitaxially grown on a substrate 11 made of a Si substrate or an SOI substrate via a buffer film 12 including a first portion PR1 and a second portion PR2.

[0062] Furthermore, in this first modified example, similar to the first embodiment, by adjusting the temperature and pressure conditions when forming the buffer film 12, the portion with a high content of the metal element M that partially stabilizes HZO, etc., can have a cubic crystal structure, while the portion with a low content of the metal element M that partially stabilizes HZO, etc., can have a tetragonal crystal structure. Therefore, even when forming the buffer film 12 in a vacuum deposition apparatus, it is possible to prevent or suppress fluctuations in its crystal structure due to temperature conditions, etc., when forming the film, and to stably form a buffer film 12 having the same crystal structure. Also, even when forming a conductive film 13 made of Pt on the buffer film 12, it is possible to stably form a conductive film 13 having the same orientation direction and film quality.

[0063] Table 1 shows preferred examples of the first metal oxide (the same applies to the third metal oxide described later). Table 1 shows preferred examples of the first metal oxide and the standard Gibbs free energy of formation (kJmol) for each first metal oxide. －１ The value of ) is shown, and represents the value described in Non-Patent Document 1.

[0064]

[0065] HfO ２ , ZrO ２ Including the above, the standard Gibbs free energy of formation values ​​for each of the first metal oxides shown in Table 1 are SiO ２ It is lower than the standard Gibbs free energy of formation. In such cases, the metal elements contained in each first metal oxide are SiO on the Si substrate. ２ By reducing and then oxidizing itself, each first metal oxide is formed on the Si substrate. ２ They can be grown directly without the need for a film (the same applies to tertiary metal oxides).

[0066] Preferably, the first portion PR1 consists of a first metal oxide represented by the following compositional formula (3), and the second portion PR2 consists of a second metal oxide represented by the following compositional formula (4). (Hf １－ｘ１－ｙ１ Zr ｘ１ M ｙ１ ) O ２－ｚ１ ... (3) (However, in composition formula (3), M is one or more elements selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) (Hf １－ｘ２－ｙ２ Zr ｘ２ M ｙ２ ) O ２－ｚ２ ... (4) (However, in composition formula (4), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) In composition formula (3) and composition formula (4) above, y1 satisfies 0 < y1 ≤ 0.3, x1 satisfies 0 < x1 ≤ 1 - y1, y2 satisfies 0 ≤ y2 < 0.3, x2 satisfies 0 ≤ x2 ≤ 1 - y2, and y1 and y2 satisfy y2 < y1. Furthermore, the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

[0067] In the following, among the metal oxides represented by the above compositional formula (3), those satisfying 0 < x1 < 1 may be referred to as HZO (the same applies to x2 in the above compositional formula (4) and x3 in the compositional formula (5) described later). In that case, the first part PR1 is ZrO partially stabilized with the metal element M. ２ Alternatively, it consists of HZO, and the second part PR2 is HZO or HfO that is partially stabilized with a metal element M. ２ Furthermore, the content of metal element M in the first part PR1 is greater than the content of metal element M in the second part PR2.

[0068] In such cases, the first metal oxide is more easily partially stabilized and more likely to have a cubic crystal structure than the second metal oxide. Therefore, when the buffer film 12 is formed in the temperature range RG1 shown in Figure 8, it is easy to control the crystal structure so that the first metal oxide has a cubic crystal structure and the second metal oxide has a tetragonal crystal structure, thereby preventing or suppressing fluctuations in the crystal structure due to temperature conditions during the formation of the buffer film 12.

[0069] As shown in Figure 11, preferably, the second portion PR2 is adjacent to the first portion PR1 in a first direction along the main surface 11p, and the buffer film 12 is positioned on the opposite side of the second portion PR2 from the first portion PR1 in the first direction, and includes a third portion PR3 adjacent to the second portion PR2. The third portion PR3 consists of a third metal oxide represented by the following composition formula (5). (Hf １－ｘ３－ｙ３ Zr ｘ３ M ｙ３ ) O ２－ｚ３ ... (5) (However, in composition formula (5), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) In composition formula (4) and composition formula (5) above, y3 satisfies 0 < y3 ≤ 0.3, x3 satisfies 0 < x3 ≤ 1 - y3, and y2 and y3 satisfy y3 > y2. Furthermore, the third metal oxide has a cubic crystal structure and is (100) oriented.

[0070] In such cases, the third metal oxide is more easily partially stabilized and more likely to have a cubic crystal structure than the second metal oxide. Therefore, it is easy to control the crystal structure so that each of the first and third metal oxides has a cubic crystal structure, and the second metal oxide has a tetragonal crystal structure, thereby preventing or suppressing fluctuations in the crystal structure due to temperature conditions, etc., when forming the buffer film 12.

[0071] Furthermore, the dynamic lattice matching effect due to the twinning martensitic transformation exhibited by the first and third metal oxides is smaller than the dynamic lattice matching effect due to the twinning martensitic transformation exhibited by the second metal oxide. Therefore, when the conductive film 13, conductive film 14, and piezoelectric film 15 undergo epitaxial growth, the dynamic lattice matching effect in the first direction in the second portion PR2 is suppressed by the first portion PR1 and the third portion PR3 acting as a kind of barrier. For this reason, if the materials of the conductive film 13, conductive film 14, and piezoelectric film 15 are suitable for a dynamic lattice matching effect in the first direction that is smaller than the dynamic lattice matching effect in the first embodiment, the conductive film 13, conductive film 14, and piezoelectric film 15 can be easily epitaxially grown by using the laminated structure of this first modification.

[0072] As shown in Figure 11, preferably, the second portion PR2 includes a film portion 12a formed on the main surface 11p and a pyramidal portion 12b protruding from the upper surface of the film portion 12a.

[0073] In this first modified example, as in the first embodiment, the (111) plane of a metal film made of, for example, Pt, is more easily grown on the side surface of the pyramidal portion 12b, which makes it easier for the metal film to be (100) oriented in cubic crystal representation on the buffer film 12, and makes it easier for a metal film made of a single crystal to be formed.

[0074] As shown in Figure 11 and also in Figure 2, preferably, when viewed from the <100> direction (Si<100> direction) along the main surface 11p of the Si(100) substrate, or from the <100> direction along the main surface 11p of the SOI layer, the angle a1 between the side SD1 of the pyramidal portion 12b and the main surface 11p is 40 to 50°, and more preferably approximately 45°.

[0075] In the example shown in Figure 12, the second portion PR2 has a tetragonal crystal structure and ZrO ２ In the two unit cells UC1, each of the eight Zr atoms is replaced by Hf, resulting in a tetragonal crystal structure and HfO ２ A single unit cell UC2 is generated. In such an example, the angle b1 (see Figure 7) between the ridge line RD1 connecting the two Hf elements in the unit cell UC2, one located at the body center and the other at the vertex, and the upper surface of the unit cell UC2 is approximately 45°. Therefore, when viewed from the <100> direction (Si<100> direction) along the main surface of the Si(100) substrate, the angle a1 between the side SD1 of the pyramidal portion 12b and the main surface 11p is approximately 45°. One possible reason for the formation of the pyramidal portion 12b is that slip deformation occurs along the ridge line RD1.

[0076] Preferably, the buffer film 12 includes a fourth portion PR4 positioned between the first portion PR1 and the third portion PR3 in the first direction, and the fourth portion PR4 consists of a fourth metal oxide represented by the following compositional formula (6). (Hf １－ｘ４－ｙ４ Zr ｘ４ M ｙ４ ) O ２－ｚ４ ... (6) (However, in composition formula (6), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) In composition formulas (3), (4), (5), and (6) above, y4 satisfies 0 ≤ y4 < 0.3, x4 satisfies 0 < x4 ≤ 1 - y4, x2 and x4 satisfy x4 > x2, y1 and y4 satisfy y4 < y1, and y3 and y4 satisfy y4 < y3. Furthermore, the fourth metal oxide has a cubic crystal structure and is (100) oriented.

[0077] In such cases, the first and third metal oxides are more easily partially stabilized and more likely to have a cubic crystal structure than the fourth metal oxide. Furthermore, the Zr / Hf ratio in the fourth metal oxide is greater than that in the second metal oxide, making it more likely to have a cubic crystal structure. Therefore, it is easy to control the crystal structure so that the first, third, and fourth metal oxides each have a cubic crystal structure, and the second metal oxide has a tetragonal crystal structure, thereby preventing or suppressing fluctuations in the crystal structure due to temperature conditions during the deposition of the buffer film 12.

[0078] Preferably, the second metal oxide is oriented such that the <100> direction along the main surface 11p of the second metal oxide is parallel to the <110> direction along the main surface 11p of the Si(100) substrate (Si<110> direction), or to the <110> direction along the main surface 11p of the SOI layer, and the fourth metal oxide is oriented such that the <100> direction along the main surface 11p of the fourth metal oxide is parallel to the <100> direction along the main surface 11p of the Si(100) substrate (Si<100> direction), or to the <100> direction along the main surface 11p of the SOI layer.

[0079] As explained using Figure 8 above, the inventors have found that the buffer film is HfO ２ In the case where the buffer film is ZrO, the temperature range in which a metal oxide with a monoclinic crystal structure is deposited, the temperature range in which a metal oxide with a tetragonal crystal structure is deposited, and the temperature range in which a metal oxide with a cubic crystal structure is deposited are such that the buffer film is ZrO ２ We found that, compared to the case where both conditions are met, they are both on the higher temperature side.

[0080] Therefore, when the buffer film 12 is formed in the temperature range RG1 shown in Figure 8, the fourth metal oxide having a Zr / Hf ratio greater than that of the second metal oxide can have a cubic crystal structure, and the second metal oxide having a Zr / Hf ratio smaller than that of the fourth metal oxide can have a tetragonal crystal structure.

[0081] In this way, because the buffer film 12 has two parts, a second part PR2 and a fourth part PR4, each having a different Zr / Hf ratio, it is possible to prevent or suppress fluctuations in its crystal structure due to temperature conditions during film formation, and to stably form a buffer film 12 with the same crystal structure.

[0082] Furthermore, preferably, the second metal oxide is HfO ２ The fourth metal oxide is ZrO ２ In such a case, as shown in Figure 8, the difference in the Zr / Hf ratio between the fourth portion PR4 and the second portion PR2 can be increased, which prevents or suppresses fluctuations in the crystal structure of the buffer film 12 depending on the temperature conditions when the buffer film 12 is deposited, and allows for the stable deposition of a buffer film 12 having the same crystal structure.

[0083] Preferably, the buffer film 12 includes a fifth portion PR5 positioned between the first portion PR1 and the third portion PR3 in the first direction, and the fifth portion PR5 consists of a fifth metal oxide represented by the following compositional formula (7). (Hf １－ｘ５－ｙ５ Zr ｘ５ M ｙ５ ) O ２－ｚ５ ... (7) (However, in composition formula (7), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) In composition formulas (3), (4), (5), and (7) above, y5 satisfies 0 < y5 < 0.3, x5 satisfies 0 ≤ x5 ≤ 1 - y5, x2 and x5 satisfies x5 < x2, y1 and y5 satisfies y5 < y1, and y3 and y5 satisfies y5 < y3. Furthermore, the fifth metal oxide has a cubic crystal structure and is (100) oriented.

[0084] Preferably, the second metal oxide is oriented such that the <100> direction along the main surface 11p of the second metal oxide is parallel to the <110> direction along the main surface 11p of the Si(100) substrate (Si<110> direction), or to the <110> direction along the main surface 11p of the SOI layer, and the fifth metal oxide is oriented such that the <100> direction along the main surface 11p of the fifth metal oxide is parallel to the <100> direction along the main surface 11p of the Si(100) substrate (Si<100> direction), or to the <100> direction along the main surface 11p of the SOI layer.

[0085] As explained using Figure 8 above, when the buffer film 12 is formed in the temperature range RG1 shown in Figure 8, it is also possible that the fifth metal oxide having a Zr / Hf ratio smaller than that of the second metal oxide has a tetragonal crystal structure, and the second metal oxide having a Zr / Hf ratio larger than that of the fifth metal oxide has a cubic crystal structure.

[0086] However, by forming the buffer film 12 while increasing the temperature from a temperature range lower than the temperature range RG1 to the temperature range RG1, or by forming the buffer film 12 while decreasing the temperature from the temperature range RG1 to a temperature range lower than the temperature range RG1, the fifth metal oxide having a Zr / Hf ratio smaller than that of the second metal oxide can have a cubic crystal structure, and the second metal oxide having a Zr / Hf ratio larger than that of the fifth metal oxide can have a tetragonal crystal structure.

[0087] In such cases, the buffer film 12 has two parts, the second part PR2 and the fifth part PR5, which have different Zr / Hf ratios, respectively. This prevents or suppresses fluctuations in the crystal structure of the buffer film 12 depending on the temperature conditions during deposition, and allows for the stable deposition of a buffer film 12 with the same crystal structure.

[0088] Furthermore, when the fifth metal oxide has a tetragonal crystal structure and the second metal oxide has a cubic crystal structure, preferably the second metal oxide is ZrO ２ The fifth metal oxide is HfO ２In such cases, the difference in the Zr / Hf ratio between the fifth portion PR5 and the second portion PR2 can be increased, which prevents or suppresses fluctuations in the crystal structure of the buffer film 12 depending on the temperature conditions when the buffer film 12 is deposited, and allows for the stable deposition of a buffer film 12 having the same crystal structure.

[0089] <Second Modification of the Laminated Structure> Next, a second modification of the laminated structure of Embodiment 1 will be described. The laminated structure of the second modification of Embodiment 1 differs from the laminated structure of Embodiment 1 in that the buffer film 12 includes a third portion which is different from both the first portion and the second portion.

[0090] Figure 13 is a cross-sectional view showing an example of a laminated structure of a second modification of Embodiment 1. The laminated structure 10 shown in Figure 13, like the laminated structure 10 of Embodiment 1, has a substrate 11 made of a Si substrate and including a main surface 11p, and a buffer film (first film) 12 formed on the main surface 11p. Alternatively, although not shown, the laminated structure of this second modification can also use a substrate 11 made of an SOI substrate as described above using Figure 2. The Si substrate is made of a Si(100) substrate, and the SOI layer is made of a Si(100) film.

[0091] In this second modification, similar to the first embodiment, the buffer film 12 includes a first portion PR1 and a second portion PR2 that is different from the first portion PR1. The first portion PR1 is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf. The second portion PR2 is made of a second metal oxide containing Hf.

[0092] On the other hand, in this second modified example, unlike the first embodiment, the buffer film 12 includes a third portion PR3 which is different from both the first portion PR1 and the second portion PR2. The third portion PR3 consists of a third metal oxide containing Hf. The first metal oxide has a cubic crystal structure and is (100) oriented, the second metal oxide has a tetragonal crystal structure and is (001) oriented, and the third metal oxide has a monoclinic crystal structure and is (100) oriented or (001) oriented.

[0093] In such cases, by adjusting the temperature and pressure conditions when depositing the buffer film 12, for example, the portion with the highest Zr / Hf ratio can have a cubic crystal structure, the portion with an intermediate Zr / Hf ratio can have a tetragonal crystal structure, and the portion with the lowest Zr / Hf ratio can have a monoclinic crystal structure. Therefore, even when depositing the buffer film in a vacuum deposition apparatus, it is possible to further prevent or suppress fluctuations in the crystal structure due to temperature conditions during film deposition, and to deposit a buffer film 12 with the same crystal structure more stably. Furthermore, even when depositing a conductive film 13 made of, for example, Pt on the buffer film 12, it is possible to deposit a conductive film 13 with the same orientation direction and film quality more stably.

[0094] Furthermore, since the first portion PR1 has a cubic crystal structure, the second portion PR2 has a tetragonal crystal structure, and the third portion PR3 has a monoclinic crystal structure, even when the conductive film and piezoelectric film on the buffer film 12 are made of a wide range of materials, a dynamic lattice matching effect due to twinning martensitic transformation can be ensured depending on the material, and high-quality conductive films and piezoelectric films can be formed.

[0095] Specifically, by, for example, forming the buffer film 12 at a temperature range RG2 (see Figure 9) lower than the temperature range RG1 shown in Figure 9, the first metal oxide can have a cubic crystal structure, the second metal oxide can have a tetragonal crystal structure, and the third metal oxide can have a monoclinic crystal structure.

[0096] Preferably, the first portion PR1 consists of a first metal oxide represented by the following compositional formula (8), the second portion PR2 consists of a second metal oxide represented by the following compositional formula (9), and the third portion PR3 consists of a third metal oxide represented by the following compositional formula (10). (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (8) (Hf １－ｘ２ Zr ｘ２ ) O ２ ... (9) (Hf １－ｘ３ Zr ｘ３ ) O ２... (10) In the above composition formulas (8), (9), and (10), x1 satisfies 0 < x1 ≤ 1, x2 satisfies 0 < x2 < 1, x3 satisfies 0 ≤ x3 < 1, and x1, x2, and x3 satisfy x3 < x2 < x1.

[0097] In such cases, the first part PR1 is ZrO ２ or consists of HZO, the second part PR2 consists of HZO, and the third part PR3 consists of HZO or HfO ２ Furthermore, the Zr / Hf ratio in the first part PR1 is greater than the Zr / Hf ratio in the second part PR2, and the Zr / Hf ratio in the second part PR2 is greater than the Zr / Hf ratio in the third part PR3. Therefore, the part with the largest Zr / Hf ratio has a cubic crystal structure, the part with an intermediate Zr / Hf ratio has a tetragonal crystal structure, and the part with the smallest Zr / Hf ratio has a monoclinic crystal structure.

[0098] Preferably, in this second modified example, as in the first embodiment, the first metal oxide is oriented such that the <100> direction along the main surface 11p of the first metal oxide is parallel to the <100> direction along the main surface 11p of the Si(100) substrate (Si<100> direction), or to the <100> direction along the main surface of the SOI layer. Preferably, the second metal oxide is oriented such that the <100> direction along the main surface 11p of the second metal oxide is parallel to the <110> direction along the main surface 11p of the Si(100) substrate (Si<110> direction), or to the <110> direction along the main surface 11p of the SOI layer. In this case, the laminated structure 10 of this second modified example has the same effects as in the first embodiment.

[0099] Furthermore, in this second modified example, preferably the first metal oxide is ZrO ２ The third metal oxide is HfO ２ In such cases, the difference in the Zr / Hf ratio between the first portion PR1 and the third portion PR3 can be increased, which prevents or suppresses fluctuations in the crystal structure of the buffer film 12 due to temperature conditions during film formation, and allows for the stable formation of a buffer film having the same crystal structure.

[0100] <Third Modification of the Laminated Structure> Next, a third modification of the laminated structure of Embodiment 1 will be described. The laminated structure of the third modification of Embodiment 1 differs from the laminated structure of Embodiment 1 in that the first portion has a tetragonal crystal structure and the second portion has a monoclinic crystal structure.

[0101] Figure 14 is a cross-sectional view showing an example of a laminated structure of a third modification of Embodiment 1. The laminated structure 10 shown in Figure 14, like the laminated structure 10 of Embodiment 1, has a substrate 11 made of a Si substrate and including a main surface 11p, and a buffer film (first film) 12 formed on the main surface 11p. Alternatively, although not shown, the laminated structure of this third modification can also use a substrate 11 made of an SOI substrate as described above using Figure 2. The Si substrate is made of a Si(100) substrate, and the SOI layer is made of a Si(100) film.

[0102] In this third modified example, similar to Embodiment 1, the buffer film 12 includes a first portion PR1 and a second portion PR2 that is different from the first portion. The first portion PR1 is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and the second portion PR2 is made of a second metal oxide containing Hf.

[0103] On the other hand, in this third modified example, unlike the first embodiment, the first metal oxide has a tetragonal crystal structure and is (001) oriented, and the second metal oxide has a monoclinic crystal structure and is (100) oriented.

[0104] In such cases, by adjusting the temperature and pressure conditions when depositing the buffer film 12, for example, the portion with a large Zr / Hf ratio can have a tetragonal crystal structure, while the portion with a small Zr / Hf ratio can have a monoclinic crystal structure. Therefore, even when depositing the buffer film in a vacuum deposition apparatus, it is possible to prevent or suppress fluctuations in its crystal structure due to temperature conditions during film deposition, and to stably deposit a buffer film 12 having the same crystal structure. Furthermore, even when depositing a conductive film 13 made of, for example, Pt on the buffer film 12, it is possible to stably deposit a conductive film 13 having the same orientation direction and film quality.

[0105] Furthermore, since the first portion PR1 has a tetragonal crystal structure and the second portion PR2 has a monoclinic crystal structure, even when the conductive film and piezoelectric film on the buffer film 12 are made of a wide range of materials, a dynamic lattice matching effect due to twinning martensitic transformation can be ensured depending on the material, and high-quality conductive films and piezoelectric films can be formed.

[0106] (Embodiment 2) Next, the laminated structure of Embodiment 2 will be described. The laminated structure of Embodiment 2 differs from the laminated structure of Embodiment 1 in that both the first and second parts have a tetragonal crystal structure.

[0107] Figure 15 is a cross-sectional view showing an example of a laminated structure according to Embodiment 2. Figures 16 and 17 show examples of the first and second parts of the laminated structure according to Embodiment 2.

[0108] The laminated structure 10 shown in Figure 15 comprises a substrate 11 including a main surface 11p, and a buffer film (first film) 12 formed on the main surface 11p.

[0109] In the example shown in Figure 15, the substrate 11 is made of a Si(100) substrate including a main surface 11p made of a Si(100) surface. Alternatively, although not shown in the figure, the laminated structure 10 of this second embodiment can also use a substrate 11 made of an SOI substrate as described above using Figure 2.

[0110] On the other hand, in this second embodiment, unlike the first embodiment, the buffer film 12 is made of a first metal oxide containing Hf and one or more metal elements selected from group 4 elements other than Hf. Furthermore, the first metal oxide has a tetragonal crystal structure and is (001) oriented.

[0111] The laminated structure 10 of this second embodiment has a tetragonal crystal structure and is (001) oriented HfO ２ A first portion PR1 consists of a tetragonal crystal structure and a (001) oriented ZrO ２Assume that the first part PR1 has a second part PR2 consisting of HfO ２ The following is an example of a part consisting of a ZrO2 having a tetragonal crystal structure and (001) orientation. ２ This illustrates the more complex parts.

[0112] In this case, similar to Embodiment 1, the conductive film 13, conductive film 14, and piezoelectric film 15 described above using Figure 10 can be easily epitaxially grown on a substrate 11 made of a Si substrate or an SOI substrate via a buffer film 12 including a first portion PR1 and a second portion PR2.

[0113] Furthermore, in this second embodiment, as in the first embodiment, by adjusting the temperature and pressure conditions when forming the buffer film 12, for example, HfO ２ The first part consists of PR1, and, for example, ZrO ２ Each of the second portion PR2 can have a tetragonal crystal structure. Therefore, buffer films 12 having the same crystal structure can be stably formed. Furthermore, even when a conductive film 13 made of Pt is formed on the buffer film 12, conductive films 13 having the same orientation direction and film quality can be stably formed.

[0114] Specifically, by, for example, depositing the buffer film 12 in a temperature range RG3 (see Figure 8) lower than the temperature range RG1 shown in Figure 8, both the first portion PR1 and the second portion PR2 can have a tetragonal crystal structure.

[0115] Preferably, the buffer film 12 consists of a first metal oxide represented by the following compositional formula (11). (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (11) In the above composition formula (11), x1 satisfies 0 ≤ x1 < 1.

[0116] In the following, among the first metal oxides represented by the above compositional formula (11), those satisfying 0 < x1 < 1 may be referred to as HZO.

[0117] In such cases, the first metal oxide is HfO ２ Although a portion of the Hf is replaced with Zr, Zr is a group 4 element and a period 5 element, and Hf is a group 4 element and a period 6 element, so their chemical properties are similar, and it is possible to prevent or suppress fluctuations in its crystal structure depending on the temperature conditions when the buffer film 12 is formed.

[0118] As shown in Figure 15, preferably, the buffer film 12 includes a film portion 12a formed on the main surface 11p and a plurality of pyramidal portions 12b each protruding from the upper surface of the film portion 12a. Each of the film portion 12a and the plurality of pyramidal portions 12b is made of a first metal oxide.

[0119] For example, if the buffer film 12 has a tetragonal crystal structure and is (001) oriented, the side surface of the pyramidal portion 12b is not a (100) plane in the cubic representation of HZO. Therefore, a (111) plane of a metal film made of, for example, Pt, is more likely to grow on the side surface of the pyramidal portion 12b, making it easier for the metal film on the buffer film 12 to be (100) oriented in the cubic representation, and thus easier for a single-crystal metal film to be formed.

[0120] As shown in Figures 15 and 16, preferably, when viewed from the <100> direction (Si<100> direction) along the main surface 11p of the Si(100) substrate, or from the <100> direction along the main surface 11p of the SOI layer, the angle a2 between each side surface SD2 of the plurality of pyramidal portions 12b and the main surface 11p is 50 to 70°, and more preferably approximately 60°.

[0121] In the examples shown in Figures 16 and 17, the crystal structure is tetragonal and ZrO ２ A unit cell UC3, which is a face-centered tetragonal lattice, is formed and has a tetragonal crystal structure and HfO ２A unit cell UC4, which is a face-centered tetragonal lattice, is generated. In such an example, the angle b2 between the side surface SD3, which connects, for example, a Zr located at the face center of the upper surface and two adjacent Zr located at positions other than the face center of the lower surface, and the upper surface of the unit cell UC3 is approximately 60°. Similarly, the angle b3 between the side surface SD4, which connects, for example, two adjacent Zr located at positions other than the face center of the lower surface, and the upper surface of the unit cell UC4, is approximately 60°. Therefore, when viewed from the <100> direction (Si<100> direction) along the main surface 11p of the Si(100) substrate, the angle between the side surface SD2 of the pyramidal portion 12b and the main surface 11p is approximately 60°. One possible reason why the pyramidal portion 12b was formed is that sliding deformation occurs along the side surface SD3 or side surface SD4.

[0122] Furthermore, preferably, in the above compositional formula (11), x1 satisfies 0.25 ≤ x1 ≤ 0.98, and the lattice constant c of the first metal oxide having a tetragonal crystal structure is 0.516 to 0.519 nm. When x1 satisfies 0.25 ≤ x1 ≤ 0.98, the first metal oxide is HfO ２ When it consists only of and the first metal oxide is ZrO ２ Compared to the case where only HZO is present, the c-axis length becomes shorter. This is thought to be because, for example, the HZO contained in the first metal oxide undergoes martensitic transformation, which shortens the c-axis length, reduces the tetragonal distortion, and approaches a cubic crystal structure.

[0123] In this second embodiment, as in the first embodiment, preferably the conductive film 13 is made of a metal having a cubic crystal structure and (100) oriented, such as a platinum group element like Pt, and the piezoelectric film 15 is made of a second metal oxide oriented (100) in a pseudocubic crystal representation. Also, in the second embodiment, as will be explained using Figure 45 in the first embodiment 11 which will be described later, the first metal oxide contained in the buffer film 12 undergoes twinning deformation or slip deformation such that the first lattice constant of the first metal oxide and the first lattice constant along the main surface 11p of the substrate 11 approaches the second lattice constant of the second metal oxide contained in the piezoelectric film 15 and the second lattice constant along the main surface 11p of the substrate 11. In such cases, the dynamic lattice matching effect due to the twinning martensitic transformation exhibited by the first metal oxide acts as a driving force, propulsion, and propulsion during the epitaxial growth of the conductive film 13, conductive film 14, and piezoelectric film 15. Therefore, the conductive film 13, conductive film 14, and piezoelectric film 15 can be easily epitaxially grown on a substrate 11 made of a Si substrate or SOI substrate via a buffer film 12.

[0124] (Embodiment 3) <Laminated Structure> Next, the laminated structure of Embodiment 3 will be described. The laminated structure of Embodiment 3 differs from the laminated structure of Embodiment 1 in that it has a second buffer film formed on a first buffer film and made of, for example, MgO.

[0125] Figure 18 is a cross-sectional view showing an example of the laminated structure of Embodiment 3. Figures 19 and 20 are cross-sectional views showing other examples of the laminated structure of Embodiment 3.

[0126] The laminated structure 20 shown in Figure 18 comprises a substrate 21 including a main surface 21p, a buffer film (first film) 22 formed on the main surface 21p, and a buffer film 23 (second film) formed on the buffer film 22.

[0127] In the example shown in Figure 18, the substrate 21 is made of a silicon (Si) substrate. Alternatively, in the example shown in Figure 19, the substrate 21 is made of an SOI substrate, which includes a base body 21a made of a Si substrate, an insulating layer 21b on the base body 21a, and an SOI layer 21c on the insulating layer 21b.

[0128] The buffer film 22 is made of a first metal compound containing Hf and one or more metal elements selected from Group 4 elements other than Hf. The buffer film 23 is made of a second metal compound containing one or more metal elements selected from Group 2 elements. Examples of the first metal compound include metal oxides, metal nitrides, or metal oxynitrides, and examples of the second metal compound include metal oxides, metal nitrides, or metal oxynitrides.

[0129] The buffer film 22 includes a film portion 22a formed on the main surface 11p, and a plurality of adjacent peaks 22c that protrude from the upper surface 22b of the film portion 22a. Between two adjacent peaks 22c, a valley portion 22d is formed. A metal portion 24a made of a platinum group element is formed in the valley portion 22d. The buffer film 23 is formed on the buffer film 22 so as to cover the side portions 22e of each of the plurality of peaks 22c and the metal portion 24a formed in the valley portion 22d.

[0130] In the laminated structure of this third embodiment, the tip portions 22f of the multiple peaks 22c are in direct contact with the buffer film 23 without the metal portion 24a (the same applies to the first and second modified examples of the third embodiment described later).

[0131] In the technology described in Patent Document 1 above, a cubic crystal structure and (100)-oriented ZrO are placed on a Si(100) substrate. ２ A conductive film made of Pt is formed via a buffer film made of . Furthermore, in the technology described in Patent Document 2 above, an HfO ２ A conductive film made of Pt is formed via an interlayer containing [a specific material].

[0132] However, ZrO ２ and HfO ２In its bulk state, Pt has a monoclinic, tetragonal, or cubic crystal structure. Therefore, when depositing a buffer film in a vacuum deposition apparatus, the crystal structure changes depending on the deposition conditions, making it difficult to stably deposit buffer films with the same crystal structure. Furthermore, the orientation direction and film quality of a conductive film made of Pt depend on the crystal structure, orientation direction, and film quality of the buffer film. Therefore, if it is not possible to stably deposit a buffer film with the same crystal structure, it is difficult to stably deposit a conductive film with the same orientation direction and film quality on the buffer film.

[0133] Furthermore, when forming a buffer film 23 made of MgO on a buffer film 22 via a conductive film made of Pt, the orientation direction and film quality of the buffer film 23 depend on the crystal structure, orientation direction, and film quality of the buffer film 22, and on the orientation direction and film quality of the conductive film made of Pt. Therefore, if it is not possible to stably deposit a buffer film 23 having the same crystal structure, and if it is not possible to stably deposit a conductive film having the same orientation direction and film quality on the buffer film 23, it is difficult to stably deposit a buffer film 23 having the same orientation direction and film quality on the conductive film.

[0134] On the other hand, in the laminated structure 20 of this third embodiment, the buffer film 23 is formed on the buffer film 22 so as to cover the side surfaces 22e of each of the multiple peaks 22c and the metal parts 24a formed on the valleys 22d, and the tip portions 22f of the multiple peaks 22c are in direct contact with the buffer film 23 without the metal parts 24a in between.

[0135] In such cases, the orientation direction of the buffer film 23 can be changed by changing the thickness TH1 of the metal portion 24a and adjusting what proportion of the side portions 22e of the peak portions 22c the metal portion 24a directly contacts without the metal portion 24a in between. That is, the inventors have found that the orientation direction of the buffer film 23 can be controlled by adjusting the thickness TH1 of the metal portion 24a and adjusting what proportion of the side portions 22e of each peak portion 22c the metal portion 24a directly contacts without the metal portion 24a in between.

[0136] Preferably, a metal portion 24a is formed in the deepest part 22g of the valley portion 22d so as to cover the deepest part 22g, and the buffer film 23 is formed on the buffer film 22 so as to cover the metal portion 24a formed in the deepest part 22g of the valley portion 22d. The height (first height) HG1 of each of the multiple peaks 22c is 5 to 30 nm, and the ratio of the thickness TH1 of the metal portion 24a to the height HG1 is 0.2 or less. The metal portion 24a has a cubic crystal structure and is (111) oriented, and the buffer film 23 has a cubic crystal structure and is (111) oriented.

[0137] In such a case, for example, the metal portion 24a made of Pt is formed only in the deepest part 22g of the valley portion 22d and not in the side portion 22e of the peak portion 22c. Therefore, the orientation direction of the metal portion 24a is not affected by the orientation direction of the first metal compound in the side portion 22e of the peak portion 22c, and if the metal portion 24a is made of Pt having a face-centered cubic structure, for example, the metal portion 24a has a cubic crystal structure and is (111) oriented. Therefore, the buffer film 23 formed on the metal portion 24a also has a cubic crystal structure and is (111) oriented.

[0138] As shown in Figure 20, preferably, the laminated structure 20 of this embodiment 3 has a conductive film 25 made of, for example, Pt formed on a buffer film 23, a piezoelectric film 26 formed on the conductive film 25, and a conductive film 27 formed on the piezoelectric film 26 (the same applies to the first and second modified examples of embodiment 3 described later). In this case, by applying an electric field between the conductive film 25 and the conductive film 27, the laminated structure 20 can be operated as a piezoelectric actuator, for example.

[0139] <First Modified Example of Laminated Structure> Next, a first modified example of the laminated structure of Embodiment 3 will be described. Compared to the laminated structure 20 of Embodiment 3, the ratio of the thickness TH1 of the metal portion 24a to the height HG1 of the peak portion 22c is larger in the laminated structure 20 of Embodiment 3.

[0140] Figure 21 is a cross-sectional view showing an example of a laminated structure of the first modified embodiment of Embodiment 3. The laminated structure 20 shown in Figure 21, like the laminated structure 20 of Embodiment 3, includes a substrate 21 including a main surface 21p, a buffer film (first film) 22 formed on the main surface 21p, and a buffer film 23 (second film) formed on the buffer film 22.

[0141] In the example shown in Figure 21, the substrate 21 is made of a Si(100) substrate including a main surface 21p made of a Si(100) surface. Alternatively, although not shown in the figure, the laminated structure of this first modified example can also use a substrate 21 made of an SOI substrate as described above using Figure 19.

[0142] In this first modified example, as in Embodiment 3, the height (first height) HG1, which is the height of each of the multiple peaks 22c, is 5 to 30 nm.

[0143] On the other hand, in this first modified example, unlike the third embodiment, the ratio of the thickness TH1 of the metal portion 24a to the height HG1 is 0.25 to 0.75. The buffer film 23 has a cubic crystal structure and is (110) oriented.

[0144] In such cases, for example, the metal portion 24a made of Pt is formed not only in the deepest part 22g of the valley portion 22d, but also in the lower part of the side surface portion 22e of the peak portion 22c. Therefore, the orientation direction of the metal portion 24a is influenced by the orientation direction of the first metal compound in the side surface portion 22e of the peak portion 22c, and if the metal portion 24a is made of Pt having a face-centered cubic structure, for example, the metal portion 24a has a cubic crystal structure and is (100) oriented. On the other hand, for example, the metal portion 24a made of Pt is not formed in the upper part of the side surface portion 22e of the peak portion 22c. Therefore, the buffer film 23 is formed directly in the upper part of the side surface portion 22e of the peak portion 22c. At that time, a specific surface of the buffer film 23 made of MgO, for example, is more likely to grow on the side surface of the peak portion 22c, so that the buffer film 23 made of MgO, for example, on the buffer film 22 has a cubic crystal structure and is (110) oriented.

[0145] <Second Modification of Laminated Structure> Next, a second modification of the laminated structure of Embodiment 3 will be described. Compared to the laminated structure 20 of the second modification of Embodiment 3, the ratio of the thickness TH1 of the metal portion 24a to the height HG1 of the peak portion 22c is even larger in the laminated structure 20 of the first modification of Embodiment 3.

[0146] Figure 22 is a cross-sectional view showing an example of a laminated structure of a second modification of Embodiment 3. The laminated structure 20 shown in Figure 22 also has, similar to the laminated structure 20 of Embodiment 3, a substrate 21 including a main surface 21p, a buffer film (first film) 22 formed on the main surface 21p, and a buffer film 23 (second film) formed on the buffer film 22.

[0147] In the example shown in Figure 22, the substrate 21 is made of a Si(100) substrate including a main surface 21p made of a Si(100) surface. Alternatively, although not shown in the figure, the laminated structure 20 of this second modified example can also use a substrate 21 made of an SOI substrate as described above using Figure 19. In such a case, the substrate 11 is made of an SOI substrate including a base body 21a made of a Si substrate, an insulating layer 21b on the base body 21a, and an SOI layer 21c on the insulating layer 21b that is made of a Si(100) film and includes a main surface 21p made of a Si(100) surface.

[0148] In this second modified example, as in the third embodiment, the height (first height) HG1, which is the height of each of the multiple peaks 22c, is 5 to 30 nm.

[0149] On the other hand, in this second modified example, unlike the third embodiment, the ratio of the thickness TH1 of the metal portion 24a to the height HG1 is 0.8 to 0.95. The first metal compound has a cubic crystal structure and is (100) oriented, or has a tetragonal crystal structure and is (001) oriented. The metal portion 24a has a cubic crystal structure and is (100) oriented. The buffer film 23 has a cubic crystal structure and is (100) oriented.

[0150] In such cases, the metal portion 24a, for example, made of Pt, is formed not only in the deepest part 22g of the valley portion 22d, but also on the side surface 22e of the peak portion 22c. Furthermore, the (111) plane of the metal portion 24a, for example, made of Pt, is more likely to grow on the side surface of the peak portion 22c, which makes it easier for the metal portion 24a, for example, made of Pt, to be (100) oriented on the buffer film 22. As a result, the buffer film 23 formed on the metal portion 24a also has a cubic crystal structure and is (100) oriented.

[0151] When forming an electronic device such as a surface acoustic wave (SAW) element by forming a buffer film 23 made of, for example, (100) oriented MgO on a buffer film 22 via metal parts 24a, and then forming a piezoelectric film or the like on the buffer film 23, it is sometimes desirable to make the thickness of the metal parts 24a as thin as possible in order to improve the function of the electronic device. Also, it is sometimes desirable to prevent the metal parts 24a from being electrically connected to each other.

[0152] In this second modified example, as in the third embodiment, the tips 22f of the multiple peaks 22c are in direct contact with the buffer film 23 without the metal portion 24a. In such a case, the thickness TH1 of the metal portion 24a can be reduced, and the metal portions 24a can be prevented from being electrically connected to each other.

[0153] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0154] (Example 1) [Formation of Laminated Structure] The laminated structure of Example 1 was fabricated. The laminated structure of Example 1 is the laminated structure described using Figure 10 above in Embodiment 1.

[0155] First, the crystal growth surface of the Si(100) substrate 11 (see Figure 10) was treated with reactive ion etching (RIE), and after heating in the presence of oxygen to form a thermal oxide film, the lower part of the buffer film 12 (see Figure 1) was deposited on the Si substrate by molecular beam epitaxy (MBE) without the use of oxygen, causing a thermal reaction between the metal (Hf, Zr) of the deposition source and the oxygen in the oxide film on the Si substrate. The conditions for the MBE method during this film deposition were as follows. The Hf:Zr (atomic ratio, the same applies below) value was 25:75, which was the target value. Deposition source: Hf, Zr Pressure: 2 × 10 －４ Pa thickness: 5 nm; Substrate temperature: 900-1100°C

[0156] Next, oxygen was introduced, the temperature was lowered, and the pressure was increased to deposit a buffer film 12 (see Figure 10) using the MBE method. The conditions for the MBE method during this deposition were as follows: The Hf:Zr ratio was 25:75, which was the target value. Evaporation source: Hf, Zr Pressure: 2 × 10 －２ Pa Thickness: 95 nm Substrate temperature: 800-1000°C

[0157] Next, a conductive film 13 made of Pt was formed on the buffer film 12 by sputtering. The conditions for this process are as follows: Apparatus: ULVAC sputtering apparatus QAM-4 Pressure: 1.20 × 10 －１ Pa Target: Pt Power: 100W (DC) Thickness: 80nm Substrate temperature: 450-600℃

[0158] Next, a conductive film 14 made of an SRO film was formed on the conductive film 13 by sputtering. The conditions for this process are as follows: Equipment: ULVAC sputtering apparatus QAM-4 Power: 150W (RF) Gas: Ar Pressure: 1.8 Pa Substrate temperature: 600℃ Thickness: 10 nm

[0159] Next, on the conductive film 14, a piezoelectric film 15 is made of Pb(Zr ０．６０ Ti０．４０ ) O ３ A PZT film having the following composition was formed by sputtering. The conditions for this process are as follows: Apparatus: RF magnetron sputtering apparatus Power: 2500W Gas: Ar / O ２ Pressure: 0.14 Pa; Substrate temperature: 425-525°C; Thickness: 100 nm

[0160] Next, a conductive film 16 made of Pt was formed on the piezoelectric film 15 by sputtering. The conditions for this process are as follows: Apparatus: ULVAC sputtering apparatus QAM-4 Pressure: 1.20 × 10 －１ Pa Target: Pt Power: 100W (DC) Thickness: 50nm Substrate Temperature: 450-600℃

[0161] In this way, the laminated structure of Example 1 was fabricated by forming a conductive film 16 on the piezoelectric film 15 by sputtering.

[0162] [X-ray Diffraction Measurement] After forming a buffer film 12 on the main surface 11p of the substrate 11, and before forming the conductive film 13, the laminated structure was positioned so that the diffraction plane in the θ-2θ method X-ray diffraction (XRD) measurement was parallel to the main surface 11p, and the diffraction pattern of the laminated structure was measured by the said X-ray diffraction measurement. The diffraction pattern of the laminated structure of Example 1 measured is shown in Figure 23. The XRD measurement was performed using a Rigaku SmartLab X-ray diffractometer.

[0163] As shown in Figure 23, strong diffraction peaks were observed in the diffraction pattern of the cubic (002) plane of HZO (HZO c(002)) and the cubic (004) plane (HZO c(004)), as well as strong diffraction peaks of the tetragonal (002) plane of HZO (HZO t(002)) and the tetragonal (004) plane (HZO t(004)). Therefore, based on the XRD measurement, it was revealed that in the laminated structure of Embodiment 1, one of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, and the other of the first metal oxide and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

[0164] Furthermore, with the laminated structure positioned so that the diffraction plane in the X-ray diffraction measurement is tilted at 90° with respect to the main plane 11p (in-plane measurement), a φ scan was performed on the cubic (200) plane (2θ = 35°) of HZO contained in the metal oxide. The φ scan measured for the laminated structure of Example 1 is shown in Figure 24.

[0165] As shown in Figure 24, in the φ scan, four strong diffraction peaks of the cubic (200) plane of HZO were observed at 90° intervals. That is, in the φ scan, diffraction peaks showing four-fold symmetry of HZO were observed. Therefore, it became clear that the HZO contained in the metal oxide had its crystal axes aligned in the in-plane direction along the main surface 11p of the substrate 11, i.e., it was epitaxially grown.

[0166] Furthermore, after forming the conductive film 13, conductive film 14, and piezoelectric film 15, the diffraction pattern of the laminated structure of Example 1 was measured by X-ray diffraction measurement using the θ-2θ method, with the laminated structure arranged so that the diffraction plane in the X-ray diffraction measurement was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 1 is shown in Figure 25.

[0167] As shown in Figure 25, in the diffraction pattern of Example 1, strong diffraction peaks were observed on the (002) plane of Pt, as well as on the (001) and (002) planes of PZT. Therefore, it became clear that in Example 1, the Pt contained in the conductive film 13 has a cubic crystal structure and is (100) oriented, and the PZT contained in the piezoelectric film 15 is (100) oriented in a pseudo-cubic representation.

[0168] [Transmission Electron Microscopy Measurement] For the laminated structure of Example 1, a cross-section along the stacking direction of the laminated structure was observed under magnification using transmission electron microscopy (TEM). The resulting multi-wave interference pattern is shown in Figure 26, and the electron diffraction pattern (limited field electron diffraction pattern) is shown in Figure 27. The multi-wave interference pattern on the right side of Figure 26 is an enlarged view of a portion of the multi-wave interference pattern on the left side of Figure 26. Furthermore, the multi-wave interference patterns on the left and right sides of Figure 26 show a cross-section perpendicular to the <100> direction of the Si(100) substrate.

[0169] As shown in the multi-wave interference images on the left and right sides of Figure 26, it became clear that the buffer film 12 includes a film portion 12a formed on the main surface 11p and a pyramidal portion 12b protruding from the upper surface of the film portion 12a. Furthermore, as shown in the multi-wave interference image on the right side of Figure 26, both pyramidal portions 12b with an angle of 42° between the side surface of the pyramidal portion 12b and the main surface 11p and pyramidal portions 12b with an angle of 56° coexisted.

[0170] Furthermore, although a detailed explanation will be omitted, in the laminated structure of Embodiment 2 described later, there were some in which the angle between the side surface of the pyramidal portion 12b and the main surface 11p was about 42°, and in the laminated structure of Embodiment 6 described later, there were some in which the angle between the side surface of the pyramidal portion 12b and the main surface 11p was about 56°. From this, it became clear that in the laminated structure of Embodiment 1 and the laminated structure of the first modified example of Embodiment 1, the angle between the side edge SD1 (see Figure 1) of the pyramidal portion 12b and the main surface 11p is 40 to 50°, and in the laminated structure of Embodiment 2, the angle between the side surface SD2 (see Figure 15) of the pyramidal portion 12b and the main surface 11p is 50 to 60°.

[0171] Furthermore, as shown in Figure 27, the electron diffraction pattern of the buffer film 12 showed a mixture of diffraction patterns of cubic HZO and tetragonal HZO. Therefore, based on the electron diffraction pattern, it became clear that in the laminated structure of Embodiment 1, one of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, while the other of the first and second metal oxides has a tetragonal crystal structure and is (001) oriented.

[0172] (Example 2) [Formation of Laminated Structure] Next, the laminated structure of Example 2 was fabricated in the same manner as in Example 1, except that when forming the buffer film 12, Hf, Zr, and Y were used instead of Hf and Zr (the values ​​of Hf:Zr:Y (atomic ratio, the same applies below) were target values, but 22.5:67.5:10), and the film formation conditions were adjusted so that the substrate temperature when forming the buffer film 12 was lower than the substrate temperature in Example 1. The laminated structure of Example 2 is the laminated structure described using Figure 11 above in the first modified example of Embodiment 1.

[0173] [X-ray diffraction measurement] For the laminated structure of Example 2, the diffraction pattern of the laminated structure was measured by X-ray diffraction measurement with the laminated structure positioned so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 2 is shown in Figure 28. In the following, HZO that is partially stabilized with Y may be referred to as YHZO.

[0174] As shown in Figure 28, in the diffraction pattern, strong diffraction peaks were observed in the cubic (002) plane of YHZO (YHZO c(002)) and the cubic (004) plane (YHZO c(004)), as well as strong diffraction peaks in the tetragonal (002) plane of YHZO (YHZO t(002)) and the tetragonal (004) plane (YHZO t(004)). Therefore, in Example 2, as in Example 1, it was revealed based on XRD measurements that one of the first and second metal oxides has a cubic crystal structure and is (100) oriented, and the other of the first and second metal oxides has a tetragonal crystal structure and is (001) oriented.

[0175] Furthermore, with the laminated structure positioned so that the diffraction plane in the X-ray diffraction measurement is tilted at 90° with respect to the main plane 11p (in-plane measurement), a φ scan was performed on the cubic (200) plane (2θ = 35°) of HZO contained in the metal oxide. Figure 29 shows the φ scan measured for the laminated structure of Example 2.

[0176] As shown in Figure 29, in the φ scan, four strong diffraction peaks of the cubic (200) plane of YHZO were observed at 90° intervals. That is, in the φ scan, diffraction peaks showing four-fold symmetry of YHZO were observed. Therefore, it became clear that the crystal axes of YHZO contained in the metal oxide are aligned in the in-plane direction along the main surface 11p of the substrate 11, i.e., that it is epitaxially grown.

[0177] [Scanning Transmission Electron Microscopy Measurement] For the laminated structure of Example 2, a cross-section along the lamination direction of the laminated structure was observed under magnification using scanning transmission electron microscopy (STEM), and compositional analysis was performed simultaneously using energy dispersive X-ray spectroscopy (EDX). The resulting STEM image and compositional analysis results are shown in Figure 30.

[0178] As shown in Figure 30, the distribution of Y is continuous in the direction perpendicular to the main surface (up and down in Figure 30), but not in the direction parallel to the main surface (left and right in Figure 30). From this result, as explained using Figure 11 above, it became clear that the buffer film 12 includes a first portion PR1, a second portion PR2, and a third portion PR3 arranged in order in the direction parallel to the main surface 11p, and that the second portion PR2, which has a lower Y content than the Y content in the first portion PR1 and the third portion PR3, is located between the first portion PR1 and the third portion PR3, which have a higher Y content than the Y content in the second portion PR2.

[0179] (Examples 3, 4, and 5) [Formation of Laminated Structures] Next, the laminated structures of Examples 3, 4, and 5 were fabricated in the same manner as in Example 1, except that the film deposition conditions were adjusted so that the substrate temperature when forming the buffer film 12 was lower than the substrate temperature in Example 1. The laminated structure 10 of Example 3 is the laminated structure described using Figure 13 above in the second modified example of Embodiment 1.

[0180] [X-ray diffraction measurement] For the laminated structures of Examples 3, 4, and 5, the diffraction patterns of the laminated structures were measured by X-ray diffraction measurement with the laminated structures arranged so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 11p. The measured diffraction patterns of the laminated structures of Examples 3, 4, and 5 are shown in Figures 31, 32, and 33.

[0181] As shown in Figure 31, in the diffraction pattern of Example 3, diffraction peaks were observed for the cubic (004) plane of HZO (HZO c(004)), strong diffraction peaks for the tetragonal (002) plane of HZO (HZO t(002)) and the tetragonal (004) plane (HZO t(004)), and diffraction peaks for the monoclinic (001) plane of HZO (HZO m(001)). Therefore, it became clear that in the laminated structure of Example 3, the first metal oxide has a cubic crystal structure and is (100) oriented, the second metal oxide has a tetragonal crystal structure and is (001) oriented, and the third metal oxide has a monoclinic crystal structure and is (100) oriented or (001) oriented.

[0182] Furthermore, as shown in Figure 32, in the diffraction pattern of Example 4, diffraction peaks of the monoclinic (001) plane of HZO (HZO m(001)), a strong diffraction peak of the monoclinic (002) plane (HZO m(002)), a diffraction peak of the monoclinic (003) plane (HZO m(003)), and a strong diffraction peak of the monoclinic (004) plane (HZO m(004)) were observed. Therefore, it became clear that in the laminated structure of Example 4, the buffer film 12 has a monoclinic crystal structure and is (100) oriented or (001) oriented.

[0183] Furthermore, as shown in Figure 33, in the diffraction pattern of Example 5, diffraction peaks were observed for the monoclinic (001) plane of HZO (HZO m(001)), the monoclinic (11-1) plane (HZO m(11-1)), the monoclinic (111) plane (HZO m(111)), a strong diffraction peak for the monoclinic (002) plane (HZO m(002)), a diffraction peak for the monoclinic (003) plane (HZO m(003)), and a strong diffraction peak for the monoclinic (004) plane (HZO m(004)). Therefore, in the laminated structure of Example 5, the buffer film 12 consists of a first metal oxide, a second metal oxide, and a third metal oxide, the first metal oxide has a monoclinic crystal structure and is (100) oriented or (001) oriented, the second metal oxide has a monoclinic crystal structure and is (11-1) oriented, and the third metal oxide has a monoclinic crystal structure and is (111) oriented.

[0184] In addition, although detailed explanations are omitted for Examples 1 to 5, the same results were obtained when the Hf:Zr ratio was other than 25:75.

[0185] (Examples 6 and 7) [Formation of Laminated Structure] Next, the laminated structure of Example 6 was fabricated in the same manner as in Example 1, except that the film deposition conditions were adjusted so that the substrate temperature when forming the buffer film 12 was lower than the substrate temperature in Example 1. The laminated structure of Example 6 is the laminated structure described using Figure 15 above in Embodiment 2.

[0186] Furthermore, multiple laminated structures of Example 7 were fabricated in the same manner as in Example 6, except that the ratio of Hf:Zr was changed from 25:75 and the substrate temperature when forming the buffer film 12 was adjusted.

[0187] [X-ray diffraction measurement] For the laminated structure of Example 6, the diffraction pattern of the laminated structure was measured by X-ray diffraction measurement with the laminated structure arranged so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 6 is shown in Figure 34.

[0188] As shown in Figure 34, in the diffraction pattern of Example 6, strong diffraction peaks were observed in the tetragonal (002) plane of HZO (HZO t(002)) and the tetragonal (004) plane (HZO t(004)). Therefore, it became clear that in the laminated structure of Example 6, the first metal oxide has a tetragonal crystal structure and is (001) oriented.

[0189] Furthermore, with the laminated structure positioned so that the diffraction plane in the X-ray diffraction measurement is tilted at 90° with respect to the main plane 11p (in-plane measurement), a φ scan was performed on the cubic (200) plane (2θ = 35°) of HZO contained in the metal oxide. Figure 35 shows the φ scan measured for the laminated structure of Example 6.

[0190] As shown in Figure 35, in the φ scan, four strong diffraction peaks of the cubic (200) plane of HZO were observed at 90° intervals. That is, in the φ scan, diffraction peaks showing four-fold symmetry of HZO were observed. Therefore, it became clear that the HZO contained in the metal oxide had its crystal axes aligned in the in-plane direction along the main surface 11p of the substrate 11, i.e., it was epitaxially grown.

[0191] Similarly, for multiple laminated structures of Example 7, the diffraction pattern of the laminated structure was measured by X-ray diffraction measurement with the laminated structure arranged so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main plane 11p, and the c-axis length of HZO was calculated from the 2θ value of the diffraction peak of the tetragonal (002) plane or tetragonal (004) plane of the measured diffraction pattern. The Zr / Hf ratio dependence of the calculated c-axis length is shown in Figure 36. Note that the horizontal axis of Figure 36 is HfO ２ This shows the proportion.

[0192] As shown in Figure 36, HfO ２ When the proportion is 2 to 75 mol%, the c-axis length is ZrO ２ c-axis length, HfO ２ The c-axis length was shorter than any of the others, and was between 0.516 and 0.519 nm. Therefore, x1 in the above compositional formula (11) satisfies 0.25 ≤ x1 < 1 ≤ 0.98, and it was revealed that the lattice constant c of the first metal oxide having a tetragonal crystal structure is between 0.516 and 0.519 nm.

[0193] (Example 8) [Formation of Laminated Structure] Next, the laminated structure of Example 8 was fabricated. The laminated structure of Example 8 is the laminated structure described using Figure 18 above in Embodiment 3. Here, if the height HG1 of each peak 22c is 20 nm, the ratio of the thickness TH1 of the metal part 24a to the height HG1 of the peak 22c was 0.1.

[0194] First, the crystal growth surface of the Si(111) substrate 21 (see Figure 18) was treated with RIE and heated in the presence of oxygen to form a thermal oxide film. Then, without using oxygen, the lower part of the buffer film 22 (see Figure 18) was deposited on the Si substrate by the MBE method, causing a thermal reaction between the metal deposition source (Hf, Zr) and the oxygen in the oxide film on the Si substrate. The conditions for the MBE method during this film deposition were as follows: The Hf:Zr values ​​were 25:75, which was the target value. －４ Pa thickness: 5 nm; Substrate temperature: 900-1100°C

[0195] Next, oxygen was introduced, the temperature was lowered, and the pressure was increased to deposit a buffer film 22 (see Figure 18) using the MBE method. The conditions for the MBE method during this deposition were as follows: The Hf:Zr ratio was 25:75, which was the target value. Evaporation source: Hf, Zr Pressure: 2 × 10 －２ Pa Thickness: 95 nm Substrate temperature: 800-1000°C

[0196] Next, a metal portion 24a made of Pt was formed on the buffer film 22 by sputtering. The conditions for this process are as follows: Apparatus: ULVAC sputtering apparatus QAM-4 Pressure: 1.20 × 10 －１ Pa Target: Pt Power: 100W (DC) Thickness: 2nm Substrate temperature: 450-600℃

[0197] Next, a buffer film 23 made of MgO was formed on the buffer film 22 by electron beam deposition so as to cover the peak portion 22c and the metal portion 24a. The conditions at this time are as follows: Deposition source: MgO Pressure: 3 × 10 －３ Pa Substrate temperature: 550℃

[0198] In this way, the laminated structure of Example 8 was fabricated by forming a buffer film 23 on the buffer film 22.

[0199] [X-ray diffraction measurement] After forming a buffer film 22, a metal part 24a, and a buffer film 23 on the main surface 21p of the substrate 21, the laminated structure was arranged so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 21p, and the diffraction pattern of the laminated structure was measured by the X-ray diffraction measurement. The diffraction pattern of the laminated structure of Example 8 measured is shown in Figure 37.

[0200] As shown in Figure 37, strong diffraction peaks were observed in the diffraction pattern for the cubic (111) plane of MgO (MgO(111)) and the cubic (222) plane (MgO(222)). Therefore, it was revealed that in the stacked structure of Embodiment 3, the buffer film 23 has a cubic crystal structure and is (111) oriented.

[0201] (Example 9) [Formation of Laminated Structure] Next, the laminated structure of Example 9 was fabricated in the same manner as in Example 8, except that the film deposition conditions for forming the metal part 24a were adjusted so that the thickness TH1 (see Figure 21) of the metal part 24a was 10 nm. The laminated structure of Example 9 is the laminated structure described using Figure 21 in the first modified example of Embodiment 3. Here, if the height HG1 of each peak 22c is 20 nm, the ratio of the thickness TH1 of the metal part 24a to the height HG1 of the peak 22c was 0.5.

[0202] [X-ray diffraction measurement] For the laminated structure of Example 9, the diffraction pattern of the laminated structure was measured by X-ray diffraction measurement with the laminated structure positioned so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 9 is shown in Figure 38.

[0203] As shown in Figure 38, a diffraction peak (MgO(220)) of the cubic (220) plane of MgO was observed in the diffraction pattern. Therefore, it became clear that in the stacked structure of the first modified example of Embodiment 3, the buffer film 23 has a cubic crystal structure and is (110) oriented.

[0204] (Example 10) [Formation of Laminated Structure] Next, the laminated structure of Example 10 was fabricated in the same manner as in Example 8, except that the film deposition conditions for forming the metal part 24a were adjusted so that the thickness TH1 (see Figure 22) of the metal part 24a was 18 nm. The laminated structure of Example 10 is the laminated structure described using Figure 22 above in the second modification of Embodiment 3. Here, if the height HG1 of each peak 22c is 20 nm, the ratio of the height of the metal part 24a to the height HG1 of the peak 22c was 0.9.

[0205] [X-ray diffraction measurement] For the laminated structure of Example 10, the diffraction pattern of the laminated structure was measured by X-ray diffraction measurement with the laminated structure positioned so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 10 is shown in Figure 39.

[0206] As shown in Figure 39, a strong diffraction peak (MgO(100)) of the cubic (100) plane of MgO was observed in the diffraction pattern. Therefore, it became clear that in the stacked structure of the second modified example of Embodiment 3, the buffer film 23 has a cubic crystal structure and is (100) oriented.

[0207] In addition, although detailed explanations are omitted for Examples 8 to 10, the same results were obtained when the Hf:Zr ratio was other than 25:75.

[0208] (Example 11) [Formation of Laminated Structure] Next, the laminated structure of Example 11 was fabricated in the same manner as in Example 1. The laminated structure of Example 11 is the laminated structure described using Figure 10 above in Embodiment 1. The substrate 11, which is a Si substrate, had a diameter of 4 inches and a thickness of 500 μm. The buffer film 12 made of HZO had a thickness of 50 nm, and the conductive film 13 made of Pt had a thickness of 100 nm, and SRO (SrRuO ３ The thickness of the conductive film 14, which is made of ), was 20 nm, and the thickness of the piezoelectric film 15, which is made of PZT, was 1000 nm.

[0209] [X-ray diffraction measurement] For the laminated structure of Example 11, the diffraction pattern of the laminated structure was measured by X-ray diffraction measurement with the laminated structure positioned so that the diffraction plane in the XRD measurement using the θ-2θ method was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 11 is shown in Figure 40.

[0210] As shown in Figure 40, in the diffraction pattern of Example 11, strong diffraction peaks were observed in the cubic (200) plane (HZO200) and cubic (400) plane (HZO400) of HZO, as well as strong diffraction peaks in the tetragonal (002) plane (HZO002) and tetragonal (004) plane (HZO004) of HZO. Therefore, based on the XRD measurement, it became clear that in the laminated structure of Embodiment 1, one of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, and the other of the first metal oxide and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

[0211] Furthermore, after forming the conductive films 13 and 14, the diffraction pattern of the laminated structure of Example 11 was measured by X-ray diffraction measurement using the θ-2θ method, with the laminated structure positioned so that the diffraction plane in the X-ray diffraction measurement of Example 11 was parallel to the main surface 11p. The measured diffraction pattern of the laminated structure of Example 11 is shown in Figure 41.

[0212] As shown in Figure 41, in the diffraction pattern of Example 11, a strong diffraction peak (Pt200) of the cubic (200) plane of Pt, and SRO (SrRuO) ３ Strong diffraction peaks (SRO100 and SRO200) were observed on the (100) and (200) planes in the pseudocubic representation of the material. Therefore, it became clear that in the laminated structure of Embodiment 1, the Pt contained in the conductive film 13 has a cubic crystal structure and is (100) oriented, and the SRO contained in the conductive film 14 is (100) oriented in the pseudocubic representation.

[0213] [Scanning Transmission Electron Microscopy Measurement] The laminated structure of Example 11 after forming the conductive film 13, conductive film 14, and piezoelectric film 15 was observed by magnifying a cross-section along the stacking direction of the laminated structure using STEM. The resulting STEM images are shown in Figures 42 and 43. Figure 42 shows the buffer film 12 made of HZO and the conductive film 13 made of Pt, and Figure 43 shows a magnified view of the area near the interface between the buffer film 12 and the conductive film 13. As shown in Figures 41 to 43, the buffer film 12 made of HZO has a characteristic pyramidal shape. That is, the buffer film 12 has a columnar or plate-like crystalline structure, and the buffer film 12 has a plurality of protrusions formed on the upper surface of the columnar or plate-like crystalline structure, and is (100) oriented. On the other hand, the conductive film 13 made of Pt has an upper surface that is much flatter than the upper surface of the buffer film 12, and is (100) oriented.

[0214] Figure 44 shows the STEM grid image of the HZO contained in the buffer film 12 of the laminated structure of Example 11, after the buffer film 12 has been formed but before the conductive film 13 has been formed. Figure 45 shows the STEM grid image of the HZO contained in the buffer film 12 of the laminated structure of Example 11, after the conductive film 13, conductive film 14, and piezoelectric film 15 have been formed.

[0215] Figure 44 shows, from left to right, a grid image at the center of a 4-inch diameter wafer, a grid image at a point 15 mm away from the center, and a grid image at the periphery 45 mm away from the center. Figure 45 also shows, from left to right, a grid image at the center of a 4-inch diameter wafer, a grid image at a point 15 mm away from the center, a grid image at a point 25 mm away from the center, and a grid image at the periphery 45 mm away from the center.

[0216] Here, as explained using Figure 3 above, HfO ２ and ZrO ２Furthermore, HZO represented by the above compositional formulas (1) and (2) is an oxide that has a fluorite-type structure, undergoes martensitic transformation, and grows epitaxially on a Si substrate. Also, as explained using Figures 4 and 5 above, twinning deformation and sliding deformation are typical examples of martensitic transformation.

[0217] As shown in Figure 44, a lattice image of HZO having a tetragonal crystal structure was similarly observed in the center of the wafer, in a portion 15 mm away from the center, and in the peripheral portion 45 mm away from the center. That is, in the laminated structure of Example 11 before the formation of the conductive film 13, a good STEM lattice image of HZO having a single-crystallized tetragonal crystal structure was confirmed across the entire surface of the Si(100) substrate with a diameter of 4 inches.

[0218] On the other hand, as shown in Figure 45, while a lattice image of HZO with a tetragonal crystal structure was obtained in the center of the wafer, a lattice image of HZO with a twinning structure and martensitic transformation (twin deformation) was observed in the part 15 mm away from the center, a lattice image of HZO with an orthorhombic crystal structure was observed in the part 25 mm away from the center, and a lattice image of slip-deformed HZO was observed in the peripheral part 45 mm away from the center. As a result, the lattice spacing, which was originally A, expanded to B, C, and D, respectively.

[0219] Thus, since the lattice spacing, which was originally A, expanded to B, C, and D, it is thought that, in the wafer periphery where the lattice mismatch of PZT becomes significant, integer multiples of lattice matching were performed by the expanded lattice constants of B, C, and D, allowing PZT with a large mismatch with Si to be epitaxially grown throughout the entire Si wafer surface. In other words, as described above, the fact that the conductive film 13, conductive film 14, and piezoelectric film 15 can be easily epitaxially grown on the substrate 11 via the buffer film 12 is due to the HfO contained in the buffer film 12. ２ , ZrO ２Alternatively, this is thought to be due to the HZO undergoing martensitic transformation. Therefore, it became clear that the first metal oxide or second metal oxide contained in the buffer film 12 undergoes twinning or slip deformation such that the first lattice constant of the first metal oxide or second metal oxide, along the main surface 11p of the substrate 11, approaches the second lattice constant of the sixth metal oxide contained in the piezoelectric film 15, along the main surface 11p of the substrate 11. Although a detailed explanation is omitted, similar results were obtained in the laminated structure of Embodiment 2, and it became clear that the first metal oxide contained in the buffer film 12 undergoes twinning or slip deformation such that the first lattice constant of the first metal oxide, along the main surface 11p of the substrate 11, approaches the second lattice constant of the second metal oxide contained in the piezoelectric film 15, along the main surface 11p of the substrate 11.

[0220] 10, 10a-10c, 20 Laminated structure 11, 21 Substrate 11a, 21a Base 11b, 21b Insulating layer 11c, 21c SOI layer 11p, 21p Main surface 12, 22, 23 Buffer film 12a, 22a Film portion 12b Pyramid portion 13, 14, 16, 25, 27 Conductive film 15, 26 Piezoelectric film 22b Top surface 22c Peak portion 22d Valley portion 22e Side portion 22f Tip portion 22g Deepest portion 24a Metal portion AT1 Metal atom HG1 Height M Metal element PR1 First part PR2 Second part PR3 Third part PR4 Fourth part PR5 Fifth part RD1 Ridge RG1-RG3 Temperature range SD1 Side SD2-SD4 Side TH1 Thickness UC1-UC4 Unit cell a1, a2, b1-b3 Angle

Claims

1. A laminated structure comprising: a substrate including a main surface; and a first film formed on the main surface, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate comprising a substrate made of a Si substrate, an insulating layer on the substrate, and an SOI layer made of a Si(100) film on the insulating layer which includes the main surface which is made of a Si(100) plane, wherein the first film comprises: a first portion; and a second portion different from the first portion, wherein the first portion is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and the second portion is made of a second metal oxide containing Hf, wherein one of the first metal oxide and the second metal oxide has a cubic crystal structure and is (100) oriented, and the other of the first metal oxide and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

2. A laminated structure according to claim 1, wherein the first portion comprises a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and one or more metal elements selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and Group 2 elements, wherein the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

3. A laminated structure according to claim 1, wherein the first film includes a third portion different from both the first portion and the second portion, the third portion is made of a third metal oxide containing Hf, the first metal oxide has a cubic crystal structure and is (100) oriented, the second metal oxide has a tetragonal crystal structure and is (001) oriented, and the third metal oxide has a monoclinic crystal structure and is (100) oriented or (001) oriented.

4. In the laminated structure according to claim 1, the first portion consists of the first metal oxide represented by the following composition formula (1): (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (1) The x1 satisfies 0 < x1 ≤ 1, and the second part consists of the second metal oxide represented by the following composition formula (2), (Hf １－ｘ２ Zr ｘ２ ) O ２ ... (2) A laminated structure in which x2 satisfies 0 ≤ x2 < 1, and x1 and x2 satisfy x2 < x1.

5. A laminated structure according to claim 4, wherein the first film includes a film portion formed on the main surface and a plurality of pyramidal portions each protruding from the upper surface of the film portion, each of the film portion and the plurality of pyramidal portions includes the first portion or the second portion, and the angle between the side of each of the plurality of pyramidal portions and the main surface is 40 to 50° when viewed from the <100> direction along the main surface of the Si(100) substrate or from the <100> direction along the main surface of the SOI layer.

6. A laminated structure according to claim 4, wherein the first metal oxide has a cubic crystal structure and is (100) oriented, and the second metal oxide has a tetragonal crystal structure and is (001) oriented.

7. A laminated structure according to claim 6, wherein the first metal oxide is oriented such that the <100> direction along the main surface of the first metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer, and the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer.

8. A laminated structure according to claim 4, wherein the first metal oxide has a tetragonal crystal structure and is (001) oriented, and the second metal oxide has a cubic crystal structure and is (100) oriented.

9. A laminated structure according to claim 8, wherein the first metal oxide is oriented such that the <100> direction along the main surface of the first metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer, and the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer.

10. In the laminated structure according to any one of claims 6 to 9, the first metal oxide is ZrO ２ The second metal oxide is HfO ２ A laminated structure.

11. In the laminate structure according to claim 2, the first part is made of the first metal oxide represented by the following composition formula (3): (Hf １－ｘ１－ｙ１ Zr ｘ１ M ｙ１ )O ２－ｚ１ ...(3) (However, in the composition formula (3), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and Group 2 elements.) y1 satisfies 0 < y1 ≤ 0.3, x1 satisfies 0 < x1 ≤ 1 - y1, the second part is made of the second metal oxide represented by the following composition formula (4): (Hf １－ｘ２－ｙ２ Zr ｘ２ M ｙ２ )O ２－ｚ２ ...(4) (However, in the composition formula (4), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and Group 2 elements.) y2 satisfies 0 ≤ y2 < 0.3, x2 satisfies 0 ≤ x2 ≤ 1 - y2, y1 and y2 satisfy y2 < y1, the first metal oxide has a cubic crystal structure and is (100)-oriented, and the second metal oxide has a tetragonal crystal structure and is (001)-oriented laminate structure.

12. In the laminated structure according to claim 11, the second portion is adjacent to the first portion in a first direction along the main surface, the first film includes a third portion that is positioned on the opposite side of the second portion in the first direction and adjacent to the second portion, and the third portion consists of a third metal oxide represented by the following compositional formula (5): (Hf １－ｘ３－ｙ３ Zr ｘ３ M ｙ３ ) O ２－ｚ３ ... (5) (wherein in composition formula (5), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) The y3 satisfies 0 < y3 ≤ 0.3, the x3 satisfies 0 < x3 ≤ 1 - y3, the y2 and y3 satisfy y3 > y2, and the third metal oxide has a cubic crystal structure and is (100) oriented, wherein the laminated structure is.

13. A laminated structure according to claim 11, wherein the second portion includes a film portion formed on the main surface and a pyramidal portion protruding from the upper surface of the film portion, and the angle between the side of the pyramidal portion and the main surface is 40 to 50° when viewed from the <100> direction along the main surface of the Si(100) substrate or from the <100> direction along the main surface of the SOI layer.

14. In the laminated structure according to claim 12, the first film includes a fourth portion disposed between the first portion and the third portion in the first direction, the fourth portion being made of a fourth metal oxide represented by the following composition formula (6): (Hf １－ｘ４－ｙ４ Zr ｘ４ M ｙ４ ) O ２－ｚ４ ... (6) (wherein in composition formula (6), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) The y4 satisfies 0 ≤ y4 < 0.3, the x4 satisfies 0 < x4 ≤ 1 - y4, the x2 and x4 satisfy x4 > x2, the y1 and y4 satisfy y4 < y1, the y3 and y4 satisfy y4 < y3, and the fourth metal oxide has a cubic crystal structure and is (100) oriented, a laminated structure.

15. A laminated structure according to claim 14, wherein the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer, and the fourth metal oxide is oriented such that the <100> direction along the main surface of the fourth metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer.

16. In the laminated structure according to claim 14 or 15, the second metal oxide is HfO ２ The fourth metal oxide is ZrO ２ A laminated structure.

17. In the laminated structure according to claim 12, the first film includes a fifth portion disposed between the first portion and the third portion in the first direction, the fifth portion being made of a fifth metal oxide represented by the following composition formula (7): (Hf １－ｘ５－ｙ５ Zr ｘ５ M ｙ５ ) O ２－ｚ５ ... (7) (However, in composition formula (7), M is one or more selected from the group consisting of Nb, Ta, Si, rare earth elements, Al, and group 2 elements.) The y5 satisfies 0 < y5 < 0.3, the x5 satisfies 0 ≤ x5 ≤ 1 - y5, the x2 and x5 satisfies x5 < x2, the y1 and y5 satisfies y5 < y1, the y3 and y5 satisfies y5 < y3, and the fifth metal oxide has a cubic crystal structure and is (100) oriented, a laminated structure.

18. A laminated structure according to claim 17, wherein the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer, and the fifth metal oxide is oriented such that the <100> direction along the main surface of the fifth metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer.

19. In the laminated structure according to claim 17 or 18, the second metal oxide is ZrO ２ The fifth metal oxide is HfO ２ A laminated structure.

20. In the laminated structure according to claim 3, the first portion consists of the first metal oxide represented by the following composition formula (8): (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (8) The x1 satisfies 0 < x1 ≤ 1, and the second part consists of the second metal oxide represented by the following composition formula (9), (Hf １－ｘ２ Zr ｘ２ ) O ２ ... (9) The x2 satisfies 0 < x2 < 1, and the third part consists of the third metal oxide represented by the following composition formula (10), (Hf １－ｘ３ Zr ｘ３ ) O ２ ... (10) A laminated structure in which x3 satisfies 0 ≤ x3 < 1, and x1, x2, and x3 satisfy x3 < x2 < x1.

21. A laminated structure according to claim 20, wherein the first metal oxide is oriented such that the <100> direction along the main surface of the first metal oxide is parallel to the <100> direction along the main surface of the Si(100) substrate or the <100> direction along the main surface of the SOI layer, and the second metal oxide is oriented such that the <100> direction along the main surface of the second metal oxide is parallel to the <110> direction along the main surface of the Si(100) substrate or the <110> direction along the main surface of the SOI layer.

22. In the laminated structure according to claim 20 or 21, the first metal oxide is ZrO ２ The third metal oxide is HfO ２ A laminated structure.

23. A laminated structure comprising: a substrate including a main surface; and a first film formed on the main surface, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate comprising a substrate made of a Si substrate, an insulating layer on the substrate, and an SOI layer made of a Si(100) film on the insulating layer and including the main surface which is made of a Si(100) plane, wherein the first film comprises: a first portion; and a second portion different from the first portion, wherein the first portion is made of a first metal oxide containing one or more metal elements selected from the group consisting of Group 4 elements other than Hf, and the second portion is made of a second metal oxide containing Hf, wherein the first metal oxide has a tetragonal crystal structure and is (001) oriented, and the second metal oxide has a monoclinic crystal structure and is (100) oriented.

24. A laminated structure comprising a substrate including a main surface and a first film formed on the main surface, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate comprising a substrate made of a Si substrate, an insulating layer on the substrate, and an SOI layer which is made of a Si(100) film on the insulating layer and includes the main surface which is made of a Si(100) plane, wherein the first film is made of a first metal oxide comprising Hf and one or more metal elements selected from group 4 elements other than Hf, and the first metal oxide has a tetragonal crystal structure and is (001) oriented.

25. In the laminated structure according to claim 24, the first film is made of the first metal oxide represented by the following composition formula (11): (Hf １－ｘ１ Zr ｘ１ ) O ２ ... (11) The x1 is a laminated structure satisfying 0 ≤ x1 < 1.

26. A laminated structure according to claim 25, wherein the first film includes a film portion formed on the main surface and a plurality of pyramidal portions each protruding from the upper surface of the film portion, each of the film portion and the plurality of pyramidal portions being made of the first metal oxide, and the angle between the side surface of each of the plurality of pyramidal portions and the main surface is 50 to 60° when viewed from the <100> direction along the main surface of the Si(100) substrate or from the <100> direction along the main surface of the SOI layer.

27. A laminated structure according to claim 25 or 26, wherein x1 satisfies 0.25 ≤ x1 ≤ 0.98, and the lattice constant c of the first metal oxide having a tetragonal crystal structure is 0.516 to 0.519 nm.

28. A laminated structure comprising: a substrate including a main surface; a first film formed on the main surface; and a second film formed on the first film, wherein the substrate is a Si substrate, or an SOI substrate comprising a substrate made of a Si substrate, an insulating layer on the substrate, and an SOI layer on the insulating layer; the first film is made of a first metal compound comprising Hf and one or more metal elements selected from group 4 elements other than Hf; the second film is made of a second metal compound comprising one or more metal elements selected from group 2 elements; the first film comprises: a film portion formed on the main surface; and a plurality of adjacent peaks protruding from the upper surface of the film portion; a valley is formed between two adjacent peaks among the plurality of peaks; a metal portion made of a platinum group element is formed in the valley; and the second film is formed on the first film so as to cover the side surfaces of each of the plurality of peaks and the metal portion formed in the valley. A laminated structure in which the tips of the multiple peaks are in direct contact with the second film without the metal portion in between.

29. A laminated structure according to claim 28, wherein the metal portion is formed in the deepest part of the valley, the second film is formed on the first film so as to cover the metal portion formed in the deepest part of the valley, the first height which is the height of each of the plurality of peaks is 5 to 30 nm, the ratio of the thickness of the metal portion to the first height is 0.2 or less, the metal portion has a cubic crystal structure and is (111) oriented, and the second film has a cubic crystal structure and is (111) oriented.

30. A laminated structure according to claim 28, wherein the first height, which is the height of each of the plurality of peaks, is 5 to 30 nm, the ratio of the thickness of the metal portion to the first height is 0.25 to 0.75, and the second film has a cubic crystal structure and is (110) oriented.

31. A laminated structure according to claim 28, wherein the substrate is a Si(100) substrate including the main surface which is made of a Si(100) plane, or an SOI substrate including the substrate which is made of a Si substrate, the insulating layer on the substrate, and the SOI layer which is made of a Si(100) film on the insulating layer and includes the main surface which is made of a Si(100) plane, the first height which is the height of each of the plurality of peaks is 5 to 30 nm, the ratio of the thickness of the metal part to the first height is 0.8 to 0.95, the first metal compound has a cubic crystal structure and is (100) oriented, or has a tetragonal crystal structure and is (001) oriented, the metal part has a cubic crystal structure and is (100) oriented, and the second film has a cubic crystal structure and is (100) oriented.

32. A laminated structure according to any one of claims 2 to 9, any one of claims 11 to 15, claim 17 or 18, claim 20 or 21, or claim 23, comprising: a conductive film formed on the first film; and a piezoelectric film formed on the conductive film, wherein the conductive film has a cubic crystal structure and is made of a (100) oriented metal; the piezoelectric film is made of a sixth metal oxide that is (100) oriented in pseudocubic crystal representation; and the first metal oxide or the second metal oxide is twinned or slip deformed such that the first lattice constant along the main surface of the first metal oxide or the second metal oxide approaches the second lattice constant along the main surface of the sixth metal oxide.

33. A laminated structure according to any one of claims 24 to 26, comprising: a conductive film formed on the first film; and a piezoelectric film formed on the conductive film, wherein the conductive film has a cubic crystal structure and is made of a (100) oriented metal; the piezoelectric film is made of a second metal oxide that is (100) oriented in pseudocubic crystal representation; and the first metal oxide is twinned or slip deformed such that the first lattice constant along the main surface of the first metal oxide approaches the second lattice constant along the main surface of the second metal oxide.

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