Elastic wave device

Abstract

Provided is an elastic wave device in which the relative bandwidth can be easily adjusted. This elastic wave device (1) is provided with: a piezoelectric substrate having a piezoelectric layer (5); and a functional electrode (IDT electrode (7)) provided on the piezoelectric layer (5) and having a plurality of electrode fingers (a plurality of first and second electrode fingers (18, 19)). The piezoelectric layer (5) has at least a first region (A) and a second region (B), the crystal orientations of which differ from each other. In a plan view, the functional electrode overlaps the first region (A) and the second region (B).

Description

Technical Field

[0001] The present invention relates to elastic wave devices. Background Art

[0002] In the past, elastic wave devices were widely used in filters of portable phones and the like. An example of a surface acoustic wave device is disclosed in the following patent document 1. In this surface acoustic wave device, a crystal orientation adjustment film is provided on a portion of a substrate. A piezoelectric film is provided over the portion of the substrate where the crystal orientation adjustment film is provided and the portion where the crystal orientation adjustment film is not provided. Thus, the directions of the c-axis in the portion of the piezoelectric film provided on the crystal orientation adjustment film and the portion not provided on the crystal orientation adjustment film are different from each other. Comb-tooth electrodes are provided in the portions of the piezoelectric film where the directions of the c-axis are different from each other. Thus, the portions of the piezoelectric film where the directions of the c-axis are different from each other constitute resonators.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-009173 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the surface acoustic wave device described in Patent Document 1, resonators are independently formed in portions of the piezoelectric thin film where the c-axes are oriented in different directions. However, it is difficult to adjust the relative bandwidth of these resonators.

[0008] An object of the present invention is to provide an elastic wave device capable of easily adjusting a relative bandwidth.

[0009] Technical solutions to solve problems

[0010] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode arranged on the piezoelectric layer and having a plurality of electrode fingers, the piezoelectric layer having at least a first region and a second region having different crystal orientations from each other, and when viewed from above, the functional electrode overlaps the first region and the second region.

[0011] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode, at least a portion of which is buried in the piezoelectric substrate, the piezoelectric substrate having at least a first region and a second region having different crystal orientations, and the piezoelectric layer having at least one of the first region and the second region.

[0012] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode arranged on the piezoelectric layer and having a plurality of electrode fingers, wherein the piezoelectric layer has at least a first region and a second region having different crystal structures from each other, and when viewed from above, the functional electrode overlaps the first region and the second region.

[0013] In another broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode at least partially buried in the piezoelectric substrate, the piezoelectric substrate having at least a first region and a second region having different crystal structures from each other, and the piezoelectric layer having at least one of the first region and the second region.

[0014] Effects of the Invention

[0015] According to the elastic wave device according to the present invention, the relative bandwidth can be easily adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0017] Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0018] Figure 3 It is along Figure 2 Schematic cross-sectional view along line II-II in FIG.

[0019] Figure 4 (a) is a schematic diagram showing the crystal structure in the first region, Figure 4 (b) is a schematic diagram showing the crystal structure in the second region.

[0020] Figure 5 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a second embodiment of the present invention.

[0021] Figure 6 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a third embodiment of the present invention.

[0022] Figure 7 It is along Figure 6 Schematic cross-sectional view along line III-III in FIG.

[0023] Figure 8 1 is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a fourth embodiment of the present invention.

[0024] Fig. 9 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a fifth embodiment of the present invention.

[0025] Fig.10 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a modification of the fifth embodiment of the present invention. DETAILED DESCRIPTION

[0026] Below, while referring to the attached Figure 1 The present invention will be clarified by describing specific embodiments of the present invention.

[0027] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined between different embodiments.

[0028] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention. Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0029] like Figure 1 as well as Figure 2 As shown, the elastic wave device 1 includes a piezoelectric substrate 2. Figure 2 As shown, the piezoelectric substrate 2 includes a support substrate 3, an intermediate layer 4, and a piezoelectric layer 5. That is, the "piezoelectric substrate" means a substrate having piezoelectricity. Specifically, the support substrate 3, the intermediate layer 4, and the piezoelectric layer 5 are stacked in this order.

[0030] The intermediate layer 4 and the piezoelectric layer 5 are respectively a stacked body. More specifically, the intermediate layer 4 has a first intermediate layer 4A and a second intermediate layer 4B. The piezoelectric layer 5 has a first piezoelectric layer 5A and a second piezoelectric layer 5B. The second intermediate layer 4B is provided on the supporting substrate 3. The first intermediate layer 4A is provided on the second intermediate layer 4B. The second piezoelectric layer 5B is provided on the first intermediate layer 4A. The first piezoelectric layer 5A is provided on the second piezoelectric layer 5B. However, the intermediate layer 4 may also be a single-layer dielectric layer, etc. The piezoelectric layer 5 may also be a single-layer piezoelectric layer. Alternatively, the piezoelectric substrate 2 may also include only the piezoelectric layer 5.

[0031] An IDT electrode 7 as a functional electrode and a pair of reflectors 8A and 8B are provided on the first piezoelectric layer 5A in the piezoelectric layer 5. An alternating voltage is applied to the functional electrode to excite elastic waves. The elastic wave device 1 in this embodiment is a surface acoustic wave resonator. In addition, the elastic wave device according to the present invention may also be a filter device or a multiplexer having a plurality of elastic wave resonators.

[0032] like Figure 1 As shown, the IDT electrode 7 has a first bus bar 16 and a second bus bar 17, and a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19. The first bus bar 16 and the second bus bar 17 are opposite to each other. One end of a plurality of first electrode fingers 18 is connected to the first bus bar 16, respectively. One end of a plurality of second electrode fingers 19 is connected to the second bus bar 17, respectively. The plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interlaced with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials. In the following, the first electrode fingers 18 and the second electrode fingers 19 are sometimes recorded simply as electrode fingers. When the direction in which the plurality of electrode fingers extend is set as the electrode finger extension direction, in the present embodiment, the electrode finger extension direction is orthogonal to the elastic wave propagation direction.

[0033] The reflectors 8A and 8B face each other with the IDT electrode 7 interposed therebetween in a direction perpendicular to the direction in which the electrode fingers extend.

[0034] Figure 3 It is along Figure 2 Schematic cross-sectional view along line II-II in FIG.

[0035] The first piezoelectric layer 5A has a first region A and a second region B. In the first region A and the second region B, the crystal orientations are different from each other. In addition, the regions with different crystal orientations are not limited to the first region A and the second region B, but may be three or more. Hereinafter, the Euler angles of the first region A are set to (φ1, θ1, ψ1), and the Euler angles of the second region B are set to (φ2, θ2, ψ2). In the notation of the Euler angles (φ, θ, ψ), the first Euler angle is φ, the second Euler angle is θ, and the third Euler angle is ψ. In the present embodiment, φ1≠φ2. That is, in the first region A and the second region B, the first Euler angles are different from each other. More specifically, the difference between φ1 and φ2 is 60°. On the other hand, θ1=θ2, ψ1=ψ2. However, in the first region A and the second region B, the manner in which the crystal orientations are different from each other is not limited to the above. The difference between φ1 and φ2 may also be other than 60°. θ1≠θ2 or ψ1≠ψ2 may be satisfied. That is, the second Euler angle or the third Euler angle may be different from each other in the first region A and the second region B. Furthermore, when θ1≠θ2 or ψ1≠ψ2, φ1=φ2 may be satisfied.

[0036] In addition, it is known that even when the Euler angles (φ1, θ1, ψ1) of the first region A and the Euler angles (φ2, θ2, ψ2) of the second region B have a deviation within the range of ±5°, there is almost no effect on the electrical characteristics of the elastic wave device 1. Therefore, in this specification, when the difference between the Euler angles of the first region A and the second region B is within ±5°, the angles of the two are set to be the same. For example, strictly speaking, even when φ1 is within the range of φ2±5°, φ1=φ2. The relationship between θ1 and θ2 is the same as the relationship between ψ1 and ψ2.

[0037] like Figure 3 As shown, in the first piezoelectric layer 5A, the first region A and the second region B are mixed. When viewed from above, in the first piezoelectric layer 5A, the area of ​​the first region A is larger than the area of ​​the second region B. Specifically, in the present embodiment, the second region B is dispersed in the first region A. However, for example, there may be one or more regions with different crystallinity other than the first region A and the second region B, such as the third region. The one or more regions preferably exist as granular regions with tiny particle sizes at the interface between the first region A and the second region B or at both ends of the piezoelectric layer 5 in the second region B in the thickness direction. As a result, deformation and stress can be reduced in the piezoelectric layer 5. On the other hand, Figure 2 The second piezoelectric layer 5B shown includes only the first region A. In this specification, the term "planar view" refers to a view from a direction corresponding to the direction of the first region. Figure 2 The elastic wave device is viewed from the top. Figure 2 For example, between the piezoelectric layer 5 side and the support substrate 3 side, the piezoelectric layer 5 side is the upper side.

[0038] The present embodiment is characterized in that the piezoelectric layer 5 has a first region A and a second region B, and the IDT electrode 7 overlaps the first region A and the second region B when viewed from above. As described above, the crystal orientations in the first region A and the second region B are different from each other. Therefore, a phase deviation occurs in the excited elastic wave. As a result, the electromechanical coupling coefficient in the present embodiment is different from the electromechanical coupling coefficient in the case where the piezoelectric layer 5 only includes the first region A. Therefore, by adjusting the ratio of the first region A and the second region B, the relative bandwidth can be easily adjusted.

[0039] In addition, when obtaining the piezoelectric layer 5 having the first region A and the second region B, for example, a film forming process may be performed on a wafer corresponding to the piezoelectric layer having only the first region A, thereby forming the piezoelectric layer having the first region A and the second region B. In this case, the crystallinity of the wafer surface is partially disrupted by surface treatment such as ion beam irradiation or plasma treatment, or the surface diffusion is reduced by lowering the film forming temperature, thereby allowing the film having the second region B to grow. By adjusting these process conditions or forming a resist pattern during the above-mentioned surface treatment, the ratio of the first region A and the second region B can be adjusted. Then, the above-mentioned wafer is divided, thereby obtaining the piezoelectric layer 5 of the elastic wave device 1.

[0040] The following describes the structure of this embodiment in further detail. Figure 2 The examples of materials of each layer in the piezoelectric substrate 2 shown in the figure are described. In this specification, a certain component includes a case where a certain material is contained in a trace amount of impurities to the extent that the electrical characteristics of the elastic wave device are not significantly deteriorated. In this specification, the so-called main component refers to a component that accounts for more than 50wt%. The material of the above-mentioned main component can also exist in any state of single crystal, polycrystalline and amorphous, or in a state of mixed existence of them.

[0041] For the first piezoelectric layer 5A and the second piezoelectric layer 5B in the piezoelectric layer 5, for example, LiNbO which is an oxide piezoelectric material can be used. 3 Lithium niobate, or LiTaO 3 In the present embodiment, the first piezoelectric layer 5A and the second piezoelectric layer 5B contain lithium tantalate or lithium niobate, which is a rhombohedral crystal material. Therefore, the crystal structure of both the first region A and the second region B is a rhombohedral crystal. Figure 4 (a) and Figure 4 (b) is shown.

[0042] Figure 4 (a) is a schematic diagram showing the crystal structure in the first region. Figure 4 (b) is a schematic diagram showing the crystal structure in the second region.

[0043] exist Figure 4 (a) and Figure 4(b) shows an example in which θ1 and θ2 of the Euler angles (φ1, θ1, ψ1) of the first region A and the Euler angles (φ2, θ2, ψ2) of the second region B are 60°. Moreover, as described above, the difference between φ1 and φ2 is 60°, and ψ1=ψ2. In the case of φ1≠φ2, θ1=θ2, and ψ1=ψ2, the crystal structure in the second region B becomes a structure rotated by the angle of the difference between φ1 and φ2 with the c-axis as the center relative to the crystal structure of the first region A. Therefore, in this embodiment, the c-axes of the first region A and the second region B are parallel.

[0044] In addition, when the first piezoelectric layer 5A and the second piezoelectric layer 5B include a rhombohedral crystal material, it can be said that the first piezoelectric layer 5A and the second piezoelectric layer 5B include a trigonal crystal material.

[0045] Return to Figure 2 In the present embodiment, the first intermediate layer 4A in the intermediate layer 4 is a low acoustic velocity film. The low acoustic velocity film is a film with a relatively low acoustic velocity. More specifically, the acoustic velocity of the body wave propagating in the low acoustic velocity film is lower than that of the body wave propagating in the first piezoelectric layer 5A, and is lower than that of the body wave propagating in the second piezoelectric layer 5B. In the present embodiment, the first intermediate layer 4A as the low acoustic velocity film contains silicon oxide. However, the material of the low acoustic velocity film is not limited to the above, and for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds in which fluorine, carbon, or boron is added to silicon oxide, or materials containing the above materials as main components can be used.

[0046] In the present embodiment, the second intermediate layer 4B in the intermediate layer 4 is a high-acoustic-velocity film as a high-acoustic-velocity material layer. The high-acoustic-velocity material layer is a layer with a relatively high acoustic velocity. More specifically, the acoustic velocity of the body wave propagating in the high-acoustic-velocity material layer is higher than the acoustic velocity of the elastic wave propagating in the first piezoelectric layer 5A, and is higher than the acoustic velocity of the elastic wave propagating in the second piezoelectric layer 5B. In the present embodiment, the second intermediate layer 4B as a high-acoustic-velocity material layer contains silicon nitride. In addition, the material of the high-acoustic-velocity material layer is not limited to the above, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, ceramics such as sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), diamond, or semiconductors such as silicon, or materials with the above materials as the main component can also be used. In addition, the spinel includes an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. Examples of the spinel include MgAl 2 O 4 、FeAl 2 O 4 、ZnAl2 O 4 、MnAl 2 O 4 .

[0047] In the present embodiment, the supporting substrate 3 includes silicon. The azimuth angle of the main surface of the supporting substrate 3 is (111). However, the azimuth angle and material of the supporting substrate 3 are not limited to the above. As the material of the supporting substrate 3, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, ceramics such as sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), diamond, or semiconductors such as silicon, or materials containing the above materials as the main components can also be used. In addition, the above-mentioned spinel contains aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. As examples of the above-mentioned spinel, MgAl 2 O 4 、FeAl 2 O 4 、ZnAl 2 O 4 、MnAl 2 O 4 .

[0048] The piezoelectric substrate 2 includes the second intermediate layer 4B as a high-acoustic-velocity material layer, the first intermediate layer 4A as a low-acoustic-velocity film, and the piezoelectric layer 5 stacked in this order. This allows the energy of elastic waves to be effectively confined in the piezoelectric layer 5 .

[0049] The IDT electrode 7, the reflector 8A, and the reflector 8B include Al. However, the materials of the IDT electrode 7 and each reflector are not limited to the above. The IDT electrode 7 and each reflector may include a laminated metal film.

[0050] An example of design parameters of the elastic wave device 1 of the present embodiment is shown below. Here, the wavelength specified by the electrode finger pitch of the IDT electrode 7 is set to λ. The electrode finger pitch is the distance between the centers of adjacent electrode fingers connected to different potentials in a direction perpendicular to the electrode finger extension direction. Specifically, when the electrode finger pitch is set to p, λ=2p.

[0051] IDT electrode 7: Material…Al, thickness…0.2λ or less

[0052] First piezoelectric layer 5A: Material: LiNbO 3 , region... the first region A and the second region B are mixed, the difference between φ1 and φ2 is 60°, and the thickness is... less than 0.66λ

[0053] Second piezoelectric layer 5B: Material: LiNbO 3 , Region… Only the first region A, Thickness… 0.34λ or more

[0054] Piezoelectric layer 5: Overall thickness: 1λ or less

[0055] First intermediate layer 4A: Material…SiO 2 , thickness…0.6λ or less

[0056] Second intermediate layer 4B: material... SiN, thickness... 0.5λ or less

[0057] Support substrate 3: Material…Si, Azimuth angle…(111)

[0058] Wavelength λ: 5μm

[0059] In addition, for example, in the above-mentioned design parameters, the material of the first piezoelectric layer 5A and the second piezoelectric layer 5B may be set to LiTaO 3 .

[0060] So far, the structure of having two regions with different crystal orientations in the piezoelectric layer has been described. In addition, the structure of the present invention is not limited to this. For example, in one embodiment of the present invention, the piezoelectric layer has two regions with different crystal structures. Figure 2 , the first piezoelectric layer 5A of the piezoelectric layer 5 has a first region A and a second region B having different crystal structures. Even with such a structure, as in the first embodiment, the electromechanical coupling coefficient can be made different relative to the case where the piezoelectric layer 5 only includes the first region A. Therefore, the relative bandwidth can be easily adjusted. In addition, the piezoelectric layer 5 may also have three or more regions having different crystal structures.

[0061] In particular, it is preferred that the piezoelectric layer 5 includes an oxide piezoelectric. The crystal structure of the oxide piezoelectric includes oxygen octahedrons. Therefore, even near the boundary between regions with different crystal structures, the mismatch between the regions can be alleviated by deformation of the oxygen octahedrons. Therefore, it is easy to obtain an epitaxial piezoelectric layer in which multiple crystal structures are mixed. Specifically, for example, in the case of lithium niobate, in addition to the most stable phase LiNbO 3 In addition to the ilmenite type, LiNb 3 O 8 , Li 3 NbO 4 、LiNbO 2 , Nb 2 O 5 , Li 2 O 2 , or NaNbO containing heterogeneous elements3 , KNbO 3 Here, as an example of a different crystal structure, LiNbO 3 Combination of LiNbO 3 The same is true for lithium tantalate.

[0062] The piezoelectric layer having two regions with different crystal structures can be obtained by the same method as the method for obtaining a piezoelectric layer having two regions with different crystal orientations. For example, by performing the above-mentioned surface treatment and film formation, a piezoelectric layer having two regions with different crystal structures can be obtained.

[0063] In this embodiment, if Figure 3 As shown, in a plan view, the IDT electrode 7 overlaps the first region A and the second region B. This effectively makes the electromechanical coupling coefficient different from the case where the piezoelectric layer 5 includes only the first region A. Therefore, the relative bandwidth can be adjusted more reliably and easily.

[0064] The following is a preferred structure of the present invention. Preferably, at least one electrode finger of the IDT electrode 7 overlaps the first region A and the second region B in a plan view. For example, in this embodiment, Figure 3 As shown, one first electrode finger 18 overlaps the first region A and the second region B in a plan view. One second electrode finger 19 also overlaps the first region A and the second region B in a plan view. This makes it possible to more reliably and easily adjust the relative bandwidth.

[0065] It is preferable that the first region A and the second region B exist in a mixed state. In this case, no matter where the IDT electrode 7 is provided on the first piezoelectric layer 5A, the IDT electrode 7 can be provided over the first region A and the second region B. Therefore, the relative bandwidth can be adjusted more reliably and easily, and the degree of freedom in design of the elastic wave device 1 can be increased.

[0066] like Figure 2As shown, it is preferred that the first piezoelectric layer 5A and the second piezoelectric layer 5B are directly stacked. In addition, it is preferred that the first piezoelectric layer 5A has a first region A and a second region B, and the second piezoelectric layer 5B is a piezoelectric single crystal layer containing only the first region A. In this case, by performing a film forming process on the second piezoelectric layer 5B, a layer containing a piezoelectric material is epitaxially grown, thereby making it easy to form the first piezoelectric layer 5A. However, the second piezoelectric layer 5B may not necessarily be a piezoelectric single crystal layer. In the case where the second piezoelectric layer 5B contains the first region A, the second piezoelectric layer 5B may also contain trace defects to the extent that the electrical characteristics of the elastic wave device 1 are not significantly deteriorated. In this case, the second piezoelectric layer 5B can be easily formed by liquid phase growth.

[0067] The piezoelectric materials of the first piezoelectric layer 5A and the second piezoelectric layer 5B are preferably of the same kind. In this case, when the first piezoelectric layer 5A is formed by epitaxial growth on a wafer corresponding to the second piezoelectric layer 5B, the crystallinity of the first piezoelectric layer 5A can be improved. Therefore, the electrical characteristics of the elastic wave device 1 can be improved. Specifically, for example, the Q value can be improved. In addition, as described above, the piezoelectric layer 5 of the elastic wave device 1 is obtained by dividing the wafer. In addition, in this specification, the same kind of piezoelectric materials include piezoelectric materials with different crystallinity or orientation. The same kind of piezoelectric materials also include piezoelectric materials whose main elements constituting each piezoelectric material are the same and whose composition ratios of the main elements are different from each other. For example, piezoelectric materials containing Li, Nb and O and whose composition ratios of Li, Nb and O are different from each other are the same kind of piezoelectric materials. In addition, in the case where the main elements constituting the respective piezoelectric materials are the same and impurities are slightly doped in the respective piezoelectric materials, the same piezoelectric materials also include piezoelectric materials with different impurity concentrations. Specifically, for example, even if the concentrations of Fe or Mg doped in one and the other lithium niobate are different, the piezoelectric materials of the two are the same piezoelectric materials. Furthermore, in the case where the main elements constituting the piezoelectric materials of one and the other are the same and impurities are not doped in one piezoelectric material but impurities are slightly doped in the other piezoelectric material, the piezoelectric materials of the two are also included in the same piezoelectric materials.

[0068] In the above-mentioned example of design parameters, the thickness of the second piezoelectric layer 5B is greater than 0.34λ, and the thickness of the entire piezoelectric layer 5 is less than 1λ. As such, the thickness of the second piezoelectric layer 5B is preferably greater than 1 / 3 of the thickness of the entire piezoelectric layer 5. Furthermore, the thickness of the second piezoelectric layer 5B is more preferably greater than 1 / 2 of the thickness of the entire piezoelectric layer 5. Thus, the crystallinity of the piezoelectric layer 5 can be more reliably improved. In addition, since the thickness of the second piezoelectric layer 5B is thick, the strength in the first region A can be particularly improved. Therefore, in the piezoelectric layer 5, it is possible to make it difficult for cracks to occur.

[0069] like Figure 3 As shown, a portion of the second region B is located between the electrode fingers. Therefore, the value of the diameter of the second region B is smaller than the value of the electrode finger spacing. As such, preferably, in at least a portion of the second region B included in the first piezoelectric layer 5A, the maximum size when viewed from above is smaller than the value of the electrode finger spacing. Preferably, in all of the second regions B included in the first piezoelectric layer 5A, the maximum size when viewed from above is smaller than the value of the electrode finger spacing. Thus, in the elastic wave device 1, the excitation characteristics of the elastic waves can be more reliably made uniform. Therefore, the electrical characteristics of the elastic wave device 1 can be more reliably improved. In addition, the power resistance can also be improved.

[0070] When viewed from above, the total area of ​​the first region A is preferably larger than the total area of ​​the second region B. In this case, it is easy to adjust the area of ​​the second region B. It is noted in advance that the preferred structure shown above can be applied to both the case where the piezoelectric layer has regions with mutually different crystal orientations and the case where the piezoelectric layer has regions with mutually different crystal structures. The preferred structure involving the Euler angle shown below can be appropriately applied to the case where the piezoelectric layer has regions with mutually different crystal orientations.

[0071] In the Euler angles (φ1, θ1, ψ1) of the first region A and the Euler angles (φ2, θ2, ψ2) of the second region B, φ1≠φ2, θ1=θ2, and ψ1=ψ2 are preferably such that φ1≠φ2, θ1=θ2, and ψ1=ψ2. In this case, the c-axes of the first region A and the second region B are parallel. Thus, the first region A and the second region B in the first piezoelectric layer 5A can be easily formed on the second piezoelectric layer 5B by epitaxial growth. In addition, the crystallinity of the first piezoelectric layer 5A can be improved, and the electrical characteristics of the elastic wave device 1 can be improved.

[0072] In the Euler angles (φ1, θ1, ψ1) of the first region A and the Euler angles (φ2, θ2, ψ2) of the second region B, the difference between φ1 and φ2 is preferably 60°, 180°, or 300°. In this case, the crystal in the first region A and the crystal in the second region B are in a twin crystal relationship. Therefore, the first region A and the second region B in the first piezoelectric layer 5A can be formed more easily on the second piezoelectric layer 5B by epitaxial growth. In addition, the crystallinity of the first piezoelectric layer 5A can be further improved, and the electrical characteristics of the elastic wave device 1 can be further improved.

[0073] For example, in the first region A and the second region B, φ1≠φ2 may be satisfied, and the polarization directions may be reversed. Even in this case, the c-axes of the first region A and the second region B are parallel. Therefore, the first region A and the second region B in the first piezoelectric layer 5A can be easily formed by epitaxial growth on the second piezoelectric layer 5B. Here, in the first region A and the second region B, the so-called reverse polarization directions specifically refer to the case where the difference between θ1 and θ2 is within 180°±5°.

[0074] In the above, as a preferred example, an example in which φ1≠φ2 is shown in the Euler angles (φ1, θ1, ψ1) of the first region A and the Euler angles (φ2, θ2, ψ2) of the second region B. On the other hand, θ1≠θ2 is also preferred. In addition, θ1≠θ2 means that the polarization directions in the first region A and the second region B are different from each other. Except for the case where the polarization directions of the two regions are different from each other and the case where the polarization directions are reversed, the directions of the c-axis are different from each other.

[0075] Moreover, in the case where θ1≠θ2, for example, when film formation is performed on a wafer corresponding to the second piezoelectric layer 5B, it is sufficient to irradiate the film with an ion beam before film formation. Alternatively, in the case of film formation based on sputtering, it is sufficient to utilize the milling effect based on self-bias. Thus, it is possible to control the preferred orientation plane and easily tilt the polarization direction of the second region B relative to the polarization direction of the first region A. More specifically, for example, when LiNbO is used for the first piezoelectric layer 5A and the second piezoelectric layer 5B, 3 In this case, due to ion irradiation from the normal direction of the wafer, the c-axis direction of the crystal is tilted from the normal direction and becomes easy to grow, resulting in grains with tilted polarization directions.

[0076] It is preferable that the polarization directions are opposite to each other in the first region A and the second region B. This makes it easier to generate a phase deviation in the excited elastic wave, and makes it easier to adjust the relative bandwidth.

[0077] The preferred structure shown below can be applied to both the case where the piezoelectric layer has regions with different crystal orientations and the case where the piezoelectric layer has regions with different crystal structures. The piezoelectric layer 5 preferably includes lithium tantalate or lithium niobate, which is a rhombohedral crystal system or a trigonal crystal system. In this case, even when the first region A and the second region B are included, the electromechanical coupling coefficient can be increased more reliably. Therefore, the electrical characteristics of the elastic wave device 1 can be improved more reliably.

[0078] like Figure 2 As shown, the cross-sectional shape of each electrode finger of the IDT electrode 7 is a trapezoid. Specifically, each electrode finger has a first surface 7a, a second surface 7b and a side surface 7c. The first surface 7a and the second surface 7b are opposite to each other in the thickness direction of the electrode finger. The second surface 7b of the first surface 7a and the second surface 7b is located on the piezoelectric layer 5 side and on the supporting substrate 3 side. The side surface 7c is connected to the first surface 7a and the second surface 7b. The side surface 7c extends obliquely relative to the normal direction of the second surface 7b. However, the side surface 7c of each electrode finger can also extend parallel to the normal direction of the second surface 7b.

[0079] In addition, a protective film may be provided on the piezoelectric layer 5 so as to cover the IDT electrode 7. In this case, the IDT electrode 7 is less likely to be damaged. For example, silicon oxide, silicon nitride, or silicon oxynitride may be used for the protective film. This structure can also be applied to the mode of the present invention other than the first embodiment.

[0080] Figure 5 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of the elastic wave device according to the second embodiment.

[0081] The present embodiment is different from the first embodiment in the order of stacking the first piezoelectric layer 25A and the second piezoelectric layer 25B. Specifically, the first piezoelectric layer 25A is provided on the intermediate layer 4. The second piezoelectric layer 25B is provided on the first piezoelectric layer 25A. The IDT electrode 7 is provided on the second piezoelectric layer 25B. Except for the above-mentioned aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0082] In this embodiment, an IDT electrode 7 is provided on the second piezoelectric layer 25B as a single phase. In this case, the IDT electrode 7 is easily formed by epitaxial growth. Therefore, the power resistance can be more reliably improved. In addition, similarly to the first embodiment, by adjusting the ratio of the first region A and the second region B, the relative bandwidth can be easily adjusted.

[0083] Figure 6 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a third embodiment. Figure 7 It is along Figure 6 Schematic cross-sectional view along line III-III in FIG.

[0084] like Figure 6 As shown, the present embodiment is different from the first embodiment in that the IDT electrode 7 is embedded in the piezoelectric layer 35, and the portion covering the side surface 7c and the first surface 7a of each electrode finger in the IDT electrode 7 is the third region C. Specifically, a plurality of electrode fingers of the IDT electrode 7 are embedded in the first piezoelectric layer 35A in the piezoelectric layer 35. Except for the above-mentioned aspects, the elastic wave device 31 of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0085] In the piezoelectric layer 35, the third region C is a region of an amorphous phase. In addition, the third region C may also have a crystal structure. In this case, the crystal orientation of the third region C is different from the crystal orientation of the first region A and the second region B. Alternatively, the crystal structure of the third region C is different from the crystal structure of the first region A and the second region B.

[0086] When forming the piezoelectric layer 35 in the present embodiment, for example, after forming the second piezoelectric layer 5B, the IDT electrode 7 is formed on the second piezoelectric layer 5B. Then, for example, the first piezoelectric layer 35A may be formed by forming a film on the second piezoelectric layer 5B and the IDT electrode 7. When the film is formed, the third region C becomes a region having a different crystal orientation from the first region A and the second region B, or a region having a different crystal structure from the first region A and the second region B, or a region of an amorphous phase due to the influence of the crystallinity of the IDT electrode 7. Here, an example of design parameters of the elastic wave device 31 is shown below.

[0087] IDT electrode 7: layer structure: Pt layer / Al layer from the second piezoelectric layer 5B side, total thickness: 0.4λ or less

[0088] First piezoelectric layer 35A: Material: LiNbO 3 , region ... the first region A and the second region B are mixed, the difference between φ1 and φ2 is 60°, and the third region C covering the IDT electrode 7 is an amorphous phase region

[0089] Second piezoelectric layer 5B: Material: LiNbO 3 , Area… Area 1 A only

[0090] Piezoelectric layer 35: Overall thickness: 0.6λ or less

[0091] First intermediate layer 4A: Material…SiO 2 , thickness…0.6λ or less

[0092] Second intermediate layer 4B: material... SiN, thickness... 0.5λ or less

[0093] Support substrate 3: Material…Si, Azimuth angle…(111)

[0094] In addition, for example, in the above-mentioned design parameters, the material of the first piezoelectric layer 35A and the second piezoelectric layer 5B may be set to LiTaO. 3 In the above-mentioned design parameters, an example is taken in which the IDT electrode 7 includes a stacked metal film, but the IDT electrode 7 may also include a single-layer metal film.

[0095] In elastic wave device 31, each electrode finger of IDT electrode 7 is embedded in piezoelectric layer 35. This can increase the electrostatic capacitance. Therefore, when a desired electrostatic capacitance is obtained, elastic wave device 31 can be made small.

[0096] As in the first embodiment, in this embodiment, the crystal orientations are different in the first region A and the second region B. Therefore, a phase deviation occurs in the excited elastic wave. As a result, the electromechanical coupling coefficient in this embodiment is different from the electromechanical coupling coefficient in the case where the piezoelectric layer 35 includes only the first region A. By adjusting the ratio of the first region A and the second region B, the relative bandwidth can be easily adjusted.

[0097] In addition, when the third region C is a region having a different crystal orientation from the first region A and the second region B, the electromechanical coupling coefficient can be effectively made different from the case where the piezoelectric layer 35 includes only the first region A. Furthermore, by adjusting the ratio of the first region A and the second region B, the relative bandwidth can be adjusted more reliably and easily.

[0098] It is sufficient that at least a part of the plurality of electrode fingers is buried in the piezoelectric layer 35. However, as in the present embodiment, it is preferable that all of the plurality of electrode fingers are buried in the piezoelectric layer 35. This allows the elastic wave device 31 to appropriately increase the electrostatic capacitance.

[0099] Figure 8 1 is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a fourth embodiment.

[0100] The present embodiment is different from the first embodiment in that the second piezoelectric layer 45B includes only the fourth region D. On the other hand, the first piezoelectric layer 5A has the first region A and the second region B, similarly to the first embodiment. The piezoelectric material constituting the fourth region D is different from the piezoelectric material constituting the first region A and the second region B. Except for the above-mentioned aspects, the elastic wave device 41 of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0101] In the elastic wave device 41, specifically, the first piezoelectric layer 5A includes lithium tantalate. Therefore, the piezoelectric material constituting the first region A and the second region B is lithium tantalate. On the other hand, the second piezoelectric layer 45B includes lithium niobate. Therefore, the piezoelectric material constituting the fourth region D is lithium niobate. The crystal orientations in the first region A and the fourth region D are the same. Thus, the first piezoelectric layer 5A can be easily formed on the second piezoelectric layer 45B by epitaxial growth. In addition, the crystal orientations in the first region A and the fourth region D may not necessarily be the same. In addition, as a combination of materials for the first piezoelectric layer 5A and the second piezoelectric layer 45B, for example, the material of the first piezoelectric layer 5A may be lithium niobate, and the material of the second piezoelectric layer 45B may be lithium tantalate. Alternatively, it may be a combination of other piezoelectric materials.

[0102] In this embodiment, as in the first embodiment, the relative bandwidth can be easily adjusted by adjusting the ratio of the first region A and the second region B. In addition, the piezoelectric materials constituting the first piezoelectric layer 5A and the second piezoelectric layer 45B are different from each other, so the range of adjustment of the electrical characteristics of the elastic wave device 41 can be easily expanded.

[0103] Furthermore, in the elastic wave device according to the present invention, in the second to fourth embodiments described above, the first region A and the second region B may have different crystal structures from each other.

[0104] In the first embodiment, the first piezoelectric layer includes both the first region A and the second region B. Therefore, the first region A and the second region B include the same material. However, in the present invention, the piezoelectric substrate only needs to include at least the first region A and the second region B. The piezoelectric layer only needs to include at least one of the first region A and the second region B. For example, an insulating layer that is not a piezoelectric layer may also include one of the first region A and the second region B. This example is shown in the fifth embodiment.

[0105] Fig. 9 This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave device according to a fifth embodiment.

[0106] This embodiment differs from the first embodiment in the layer structure of the piezoelectric substrate 52, the arrangement of the regions in the piezoelectric substrate 52, and the arrangement of the IDT electrodes 7. Except for the above-described points, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0107] The piezoelectric substrate 52 is different from the piezoelectric substrate 2 of the first embodiment in that it has an insulator layer 56 and the piezoelectric layer 55 is a single layer. Specifically, in the piezoelectric substrate 52, the second intermediate layer 4B is provided on the support substrate 3. The first intermediate layer 4A is provided on the second intermediate layer 4B. The insulator layer 56 is provided on the first intermediate layer 4A. The piezoelectric layer 55 is provided on the insulator layer 56.

[0108] In this embodiment, the material of the insulator layer 56 is not a piezoelectric material. However, the material of the insulator layer 56 may be a piezoelectric material. When the material of the insulator layer 56 is not a piezoelectric material, sapphire or the like may be used as the material of the insulator layer 56, for example.

[0109] The IDT electrode 7 is provided on the insulator layer 56. Fig. 9 As shown in FIG. 1 , the piezoelectric layer 55 is provided on the insulating layer 56 so as to cover the entire IDT electrode 7. That is, the second surface 7b of each electrode finger of the IDT electrode 7 is in contact with the insulating layer 56. On the other hand, the first surface 7a and the side surface 7c of each electrode finger are in contact with the piezoelectric layer 55. Even in this case, elastic waves are excited by applying an AC voltage to the IDT electrode 7.

[0110] The insulator layer 56 includes a first region A. On the other hand, the piezoelectric layer 55 includes a second region B, a third region C, and a fourth region D. The second region B, the third region C, and the fourth region D are mixed in the piezoelectric layer 55. Specifically, in a plan view, in the piezoelectric layer 55, the total area of ​​the fourth region D is larger than the total area of ​​the second region B. More specifically, in the present embodiment, the second region B is dispersed in the fourth region D.

[0111] In a plan view, the total area of ​​the fourth region D is larger than the total area of ​​the third region C. More specifically, the third region C is located in at least a portion of the portion covering the electrode fingers in the piezoelectric layer 55. More specifically, in the present embodiment, the third region C is located in a portion of the portion covering the electrode fingers in the piezoelectric layer 55. The second region B and the fourth region D are located in another portion of the portion covering the electrode fingers in the piezoelectric layer 55. However, the third region C may be located in the entire portion covering the electrode fingers in the piezoelectric layer 55.

[0112] In this manner, the piezoelectric substrate includes the third region C, and the third region C covers at least a portion of the IDT electrode 7 as a functional electrode. This structure is also applicable to the structure in which the piezoelectric layer is a laminated body in the first embodiment and the like.

[0113] In the piezoelectric substrate 52 of the present embodiment, the crystal orientation of the first region A is different from the crystal orientation of the second region B. By adjusting the ratio of the first region A and the second region B, the relative bandwidth can be easily adjusted.

[0114] In addition, in the piezoelectric substrate 52 , the crystal structure of the first region A and the crystal structure of the second region B may be different from each other. Even in this case, the relative bandwidth can be easily adjusted by adjusting the ratio of the first region A and the second region B.

[0115] The third region C in the piezoelectric substrate 52 has a crystal structure. The crystal orientation of the third region C is different from that of the first region A and the second region B. However, the crystal structure of the third region C may be different from that of the first region A and the second region B. Alternatively, the third region C may be an amorphous phase region.

[0116] In the piezoelectric layer 55 of the piezoelectric substrate 52, the crystal orientation of the second region B and the crystal orientation of the fourth region D are different from each other. In the present invention, the fourth region D located in the piezoelectric layer 55 may also be the first region. The first region A located in the insulating layer 56 may also be the fourth region. Even in this case, the relative bandwidth can be easily adjusted by adjusting the ratio of the first region as the fourth region D located in the piezoelectric layer 55 and the second region B.

[0117] The crystal structure of the first region as the fourth region D located in the piezoelectric layer 55 and the crystal structure of the second region B may be different from each other. Even in this case, the relative bandwidth can be easily adjusted by adjusting the ratio of the first region as the fourth region D located in the piezoelectric layer 55 and the second region B.

[0118] The piezoelectric layer 55 only needs to cover at least a portion of the IDT electrode 7. In other words, at least a portion of the IDT electrode 7 only needs to be buried in the piezoelectric substrate 52. Fig.10 In the modified example of the fifth embodiment shown, the piezoelectric layer 55 covers a portion of the IDT electrode 7. Specifically, the piezoelectric layer 55 is provided on the insulating layer 56 so as to cover a portion of the side surface 7c of each electrode finger. The first surface 7a of each electrode finger is not covered by the piezoelectric layer 55. In this way, a portion of the IDT electrode 7 is embedded in the piezoelectric substrate 52A. Even in this case, elastic waves are excited by applying an AC voltage to the IDT electrode 7.

[0119] In this modification, similarly to the fifth embodiment, the insulator layer 56 in the piezoelectric substrate 52A includes the first region A. The piezoelectric layer 55 includes the second region B, the third region C, and the fourth region D. In the piezoelectric substrate 52A, the crystal orientation of the first region A and the crystal orientation of the second region B are different from each other. By adjusting the ratio of the first region A and the second region B, the relative bandwidth can be easily adjusted.

[0120] In the piezoelectric substrate 52A, the crystal structure of the first region A and the crystal structure of the second region B may be different from each other. Even in this case, the relative bandwidth can be easily adjusted by adjusting the ratio of the first region A and the second region B.

[0121] In the first to fifth embodiments and the modified examples described above, examples are shown in which the functional electrode is an IDT electrode and the elastic wave device is a surface acoustic wave device. However, the functional electrode is not limited to the IDT electrode. For example, the functional electrode may also be a plate-shaped electrode, etc. In this case, the elastic wave device may also be a BAW (Bulk Acoustic Wave) element.

[0122] More specifically, for example, the functional electrode may be a first plate-shaped electrode and a second plate-shaped electrode. The first plate-shaped electrode and the second plate-shaped electrode may be sandwiched between, for example, Figure 2 The first plate-shaped electrode and the second plate-shaped electrode are preferably overlapped over the first region A and the second region B in a plan view.

[0123] Alternatively, for example, at least a portion of at least one of the first plate-shaped electrode and the second plate-shaped electrode may be embedded in the Figure 6 The piezoelectric layer 35 shown. The first plate-shaped electrode and the second plate-shaped electrode may be opposed to each other with a portion of the piezoelectric layer 35 in the thickness direction being sandwiched therebetween. In this case, the third region C may also be located in the portion of the piezoelectric layer 35 that covers the first plate-shaped electrode or the second plate-shaped electrode. The third region C may be an amorphous region or may have a crystalline structure. In the case where the third region C has a crystalline structure, the crystal orientation of the third region C is different from the crystal orientation of the first region A and the second region B. Alternatively, the crystal structure of the third region C is different from the crystal structure of the first region A and the second region B.

[0124] Even when the functional electrode is a plate-shaped electrode, it is sufficient that the crystal orientation of the first region A and the crystal orientation of the second region B are different from each other. Alternatively, it is sufficient that the crystal structure of the first region A and the crystal structure of the second region B are different from each other. By adjusting the ratio of the first region A and the second region B, the relative bandwidth can be easily adjusted.

[0125] Examples of aspects of the elastic wave device according to the present invention are summarized below.

[0126] <1>

[0127] An elastic wave device comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, wherein the piezoelectric layer has at least a first region and a second region having different crystal orientations from each other, and when viewed from above, the functional electrode overlaps the first region and the second region.

[0128] <2>

[0129] An elastic wave device comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode at least partially buried in the piezoelectric substrate, wherein the piezoelectric substrate has at least a first region and a second region having different crystal orientations, and the piezoelectric layer has at least one of the first region and the second region.

[0130] <3>

[0131] An elastic wave device comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode, which is arranged on the piezoelectric layer and has a plurality of electrode fingers, wherein the piezoelectric layer has at least a first region and a second region having mutually different crystal structures, and when viewed from above, the functional electrode overlaps over the first region and the second region.

[0132] <4>

[0133] An elastic wave device comprises: a piezoelectric substrate having a piezoelectric layer; and a functional electrode at least partially buried in the piezoelectric substrate, wherein the piezoelectric substrate has at least a first region and a second region having mutually different crystal structures, and the piezoelectric layer has at least one of the first region and the second region.

[0134] <5>

[0135] according to <1> The elastic wave device, wherein:

[0136] The functional electrode is an IDT electrode having a plurality of electrode fingers, and at least one of the electrode fingers of the IDT electrode overlaps the first region and the second region in a plan view.

[0137] <6>

[0138] according to <2> The elastic wave device, wherein:

[0139] The functional electrode is an IDT electrode having a plurality of electrode fingers.

[0140] <7>

[0141] according to <2> or <6> The elastic wave device, wherein:

[0142] The piezoelectric substrate includes a third region covering at least a portion of the functional electrode, and the third region is an amorphous phase region or a region having a crystal orientation different from that of the first region and the second region.

[0143] <8>

[0144] according to <1> , <2> or <5> ~ <7> The elastic wave device as described in any one of the preceding claims, wherein:

[0145] The first region and the second region have polarization directions different from each other.

[0146] <9>

[0147] according to <8> The elastic wave device, wherein:

[0148] In the first region and the second region, polarization directions are opposite to each other.

[0149] <10>

[0150] according to <1> , <2> or <5> ~ <9> The elastic wave device as described in any one of the preceding claims, wherein:

[0151] When the Euler angles of the first region are (φ1, θ1, ψ1) and the Euler angles of the second region are (φ2, θ2, ψ2), φ1≠φ2.

[0152] <11>

[0153] according to <10> The elastic wave device, wherein:

[0154] In the Euler angles (φ1, θ1, ψ1) of the first region and the Euler angles (φ2, θ2, ψ2) of the second region, a difference between φ1 and φ2 is 60°, 180°, or 300°.

[0155] <12>

[0156] according to <3> The elastic wave device, wherein:

[0157] The functional electrode is an IDT electrode having a plurality of electrode fingers, and at least one of the electrode fingers of the IDT electrode overlaps the first region and the second region in a plan view.

[0158] <13>

[0159] according to <4> The elastic wave device, wherein:

[0160] The functional electrode is an IDT electrode having a plurality of electrode fingers.

[0161] <14>

[0162] according to <4> or <13> The elastic wave device, wherein:

[0163] The piezoelectric substrate includes a third region covering at least a portion of the functional electrode, and the third region is an amorphous phase region or a region having a crystal structure different from those of the first region and the second region.

[0164] <15>

[0165] according to <1> ~ <14> The elastic wave device as described in any one of the preceding claims, wherein:

[0166] The piezoelectric layer includes an oxide piezoelectric body.

[0167] <16>

[0168] according to <1> ~ <15> The elastic wave device as described in any one of the preceding claims, wherein:

[0169] The piezoelectric layer includes lithium tantalate or lithium niobate.

[0170] <17>

[0171] according to <1> ~ <16> The elastic wave device as described in any one of the preceding claims, wherein:

[0172] The piezoelectric layer includes at least a layer in which the first region and the second region are mixed.

[0173] <18>

[0174] according to <17> The elastic wave device, wherein:

[0175] The piezoelectric layer is a laminate and includes at least a first piezoelectric layer and a second piezoelectric layer. The first region and the second region are mixed in the first piezoelectric layer.

[0176] <19>

[0177] according to <18> The elastic wave device, wherein:

[0178] The second piezoelectric layer includes the first region.

[0179] <20>

[0180] according to <19> The elastic wave device, wherein:

[0181] The thickness of the second piezoelectric layer is equal to or greater than 1 / 2 of the overall thickness of the piezoelectric layer.

[0182] <21>

[0183] according to <18> The elastic wave device, wherein:

[0184] The first region and the second region include the same kind of piezoelectric material, the second piezoelectric layer includes only a fourth region, and the fourth region includes a piezoelectric material different from the piezoelectric material constituting the first region and the second region.

[0185] <22>

[0186] according to <17> ~ <20> The elastic wave device as described in any one of the preceding claims, wherein:

[0187] The first region and the second region include the same type of piezoelectric material.

[0188] <23>

[0189] according to <17> ~ <22> The elastic wave device as described in any one of the preceding claims, wherein:

[0190] In the piezoelectric layer, the total area of ​​the first regions is larger than the total area of ​​the second regions in a plan view.

[0191] Description of Reference Numerals

[0192] 1: Elastic wave device;

[0193] 2: Piezoelectric substrate;

[0194] 3: Support base plate;

[0195] 4: Middle layer;

[0196] 4A, 4B: 1st intermediate layer, 2nd intermediate layer;

[0197] 5: Piezoelectric layer;

[0198] 5A, 5B: first piezoelectric layer, second piezoelectric layer;

[0199] 7: IDT electrode;

[0200] 7a, 7b: side 1, side 2;

[0201] 7c: side view;

[0202] 8A, 8B: reflector;

[0203] 16, 17: Bus bar 1, bus bar 2;

[0204] 18, 19: first electrode finger, second electrode finger;

[0205] 25A, 25B: first piezoelectric layer, second piezoelectric layer;

[0206] 31: Elastic wave device;

[0207] 35: piezoelectric layer;

[0208] 35A: first piezoelectric layer;

[0209] 41: Elastic wave device;

[0210] 45B: second piezoelectric layer;

[0211] 52, 52A: piezoelectric substrate;

[0212] 55: piezoelectric layer;

[0213] 56: insulator layer;

[0214] A~D: Area 1~Area 4.

Claims

1. An elastic wave device comprising: a piezoelectric substrate having a piezoelectric layer; and The functional electrode is disposed on the piezoelectric layer and has a plurality of electrode fingers. The piezoelectric layer includes at least a first region and a second region having mutually different crystal orientations, and the functional electrode overlaps over the first region and the second region in a plan view.

2. An elastic wave device comprising: A piezoelectric substrate having a piezoelectric layer; and The functional electrode is at least partially embedded in the piezoelectric substrate. The piezoelectric substrate includes at least a first region and a second region having mutually different crystal orientations, and the piezoelectric layer includes at least one of the first region and the second region.

3. An elastic wave device comprising: a piezoelectric substrate having a piezoelectric layer; and The functional electrode is disposed on the piezoelectric layer and has a plurality of electrode fingers. The piezoelectric layer includes at least a first region and a second region having different crystal structures from each other, and the functional electrode overlaps the first region and the second region in a plan view.

4. An elastic wave device comprising: a piezoelectric substrate having a piezoelectric layer; and The functional electrode is at least partially embedded in the piezoelectric substrate. The piezoelectric substrate includes at least a first region and a second region having mutually different crystal structures, and the piezoelectric layer includes at least one of the first region and the second region.

5. The elastic wave device according to claim 1, in, The functional electrode is an IDT electrode having a plurality of electrode fingers, At least one of the electrode fingers of the IDT electrode overlaps the first region and the second region in a plan view.

6. The elastic wave device according to claim 2, in, The functional electrode is an IDT electrode having a plurality of electrode fingers.

7. The elastic wave device according to claim 2 or 6, in, The piezoelectric substrate includes a third region covering at least a portion of the functional electrode, and the third region is an amorphous phase region or a region having a crystal orientation different from that of the first region and the second region.

8. The elastic wave device according to any one of claims 1, 2, or 5 to 7, in, The first region and the second region have polarization directions different from each other.

9. The elastic wave device according to claim 8, in, In the first region and the second region, polarization directions are opposite to each other.

10. The elastic wave device according to any one of claims 1, 2, or 5 to 9, in, When the Euler angles of the first region are (φ1, θ1, ψ1) and the Euler angles of the second region are (φ2, θ2, ψ2), φ1≠φ2.

11. The elastic wave device according to claim 10, in, In the Euler angles (φ1, θ1, ψ1) of the first region and the Euler angles (φ2, θ2, ψ2) of the second region, a difference between φ1 and φ2 is 60°, 180°, or 300°.

12. The elastic wave device according to claim 3, in, The functional electrode is an IDT electrode having a plurality of electrode fingers, At least one of the electrode fingers of the IDT electrode overlaps the first region and the second region in a plan view.

13. The elastic wave device according to claim 4, in, The functional electrode is an IDT electrode having a plurality of electrode fingers.

14. The elastic wave device according to claim 4 or 13, in, The piezoelectric substrate includes a third region covering at least a portion of the functional electrode, and the third region is an amorphous phase region or a region having a crystal structure different from those of the first region and the second region.

15. The elastic wave device according to any one of claims 1 to 14, in, The piezoelectric layer includes an oxide piezoelectric body.

16. The elastic wave device according to any one of claims 1 to 15, in, The piezoelectric layer includes lithium tantalate or lithium niobate.

17. The elastic wave device according to any one of claims 1 to 16, in, The piezoelectric layer includes at least a layer in which the first region and the second region are mixed.

18. The elastic wave device according to claim 17, in, The piezoelectric layer is a laminate and includes at least a first piezoelectric layer and a second piezoelectric layer. In the first piezoelectric layer, the first region and the second region exist in a mixed state.

19. The elastic wave device according to claim 18, in, The second piezoelectric layer includes the first region.

20. The elastic wave device according to claim 19, in, The thickness of the second piezoelectric layer is equal to or greater than 1 / 2 of the overall thickness of the piezoelectric layer.

21. The elastic wave device according to claim 18, in, The first region and the second region include the same type of piezoelectric material, The second piezoelectric layer includes only a fourth region, and the fourth region includes a piezoelectric material different from a piezoelectric material constituting the first region and the second region.

22. The elastic wave device according to any one of claims 17 to 20, in, The first region and the second region include the same type of piezoelectric material.

23. The elastic wave device according to any one of claims 17 to 22, in, In the piezoelectric layer, the total area of ​​the first regions is larger than the total area of ​​the second regions in a plan view.

Images