Elastic wave device

Abstract

This invention provides an elastic wave device capable of suppressing unwanted waves in multiple elastic wave resonators, comprising: at least one first elastic wave resonator having a first piezoelectric layer, a second piezoelectric layer disposed on the first piezoelectric layer and having a polarization direction different from that of the first piezoelectric layer, a first IDT electrode disposed on the second piezoelectric layer, and a first dielectric film disposed on the second piezoelectric layer and covering the first IDT electrode; and at least one second elastic wave resonator sharing the first piezoelectric layer with the first elastic wave resonator, having a second IDT electrode disposed on the first piezoelectric layer, and a second dielectric film disposed on the first piezoelectric layer and covering the second IDT electrode. The distance between the first piezoelectric layer and the first IDT electrode is different from the distance between the first piezoelectric layer and the second IDT electrode. The first IDT electrode is embedded in the first dielectric film, and the second IDT electrode is embedded in the second dielectric film.

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Previously, elastic wave devices have been widely used in filters for portable telephones, etc. Several examples of elastic wave devices are disclosed in Patent Document 1 below. In one example of an elastic wave device, a laminate of two piezoelectric films is provided on a support member. An IDT (Interdigital Transducer) electrode is provided on this laminate. In an elastic wave device listed as a comparative example, a single-layer piezoelectric film is provided on the support member. An IDT electrode is provided on this piezoelectric film.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2021 / 125013

[0006] The inventors of this invention have discovered that elastic wave resonators comprising a single-layer piezoelectric film and elastic wave resonators comprising two-layer piezoelectric films can be used in the same filter device. However, the inventors of this invention have also discovered that the cut angles of the piezoelectric films capable of suppressing unwanted waves differ between the two types of elastic wave resonators. Therefore, if the two types of elastic wave resonators are used in a single filter device, it is difficult to suppress unwanted waves. The inventors of this invention have also discovered that when the thickness of the piezoelectric film differs among multiple elastic wave resonators comprising two-layer piezoelectric films, the cut angles of the piezoelectric films capable of suppressing unwanted waves also differ among these multiple elastic wave resonators. Therefore, when these multiple elastic wave resonators are used in a single filter device, it is also difficult to suppress unwanted waves. Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The purpose of this invention is to provide an elastic wave device capable of suppressing unwanted waves in multiple elastic wave resonators.

[0009] Technical solutions for solving the problem

[0010] The elastic wave device of the present invention includes at least one first elastic wave resonator and at least one second elastic wave resonator. The first elastic wave resonator has: a first piezoelectric layer; a second piezoelectric layer disposed on the first piezoelectric layer; a first IDT electrode disposed on the second piezoelectric layer and having a plurality of electrode fingers; and a first dielectric film disposed on the second piezoelectric layer such that it covers the first IDT electrode. The second elastic wave resonator is an elastic wave resonator that shares the first piezoelectric layer with the first elastic wave resonator and has: a second IDT electrode. A first piezoelectric layer is disposed directly or indirectly on the first piezoelectric layer and has a plurality of electrode fingers; and a second dielectric film is disposed directly or indirectly on the first piezoelectric layer such that it covers the second IDT electrode. The distance between the first piezoelectric layer and the first IDT electrode and the distance between the first piezoelectric layer and the second IDT electrode are different from each other. The polarization directions of the first piezoelectric layer and the second piezoelectric layer are different from each other. The first IDT electrode is embedded in the first dielectric film, and the second IDT electrode is embedded in the second dielectric film.

[0011] Invention Effects

[0012] According to the elastic wave device of the present invention, unwanted waves in multiple elastic wave resonators can be suppressed. Attached Figure Description

[0013] Figure 1 This is a schematic top view of the elastic wave device according to the first embodiment of the present invention.

[0014] Figure 2 This is a schematic front sectional view showing the vicinity of a pair of electrode fingers of the first elastic wave resonator and the vicinity of a pair of electrode fingers of the second elastic wave resonator in the first embodiment of the present invention.

[0015] Figure 3 This is a schematic front sectional view near a pair of electrode fingers of a comparative example elastic wave resonator.

[0016] Figure 4 This is a graph showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the phase of the Rayleigh wave in the elastic wave resonator of the comparative example.

[0017] Figure 5 This is a schematic front sectional view near a pair of electrode fingers of an elastic wave resonator having the same structure as the first and second elastic wave resonators in the first embodiment of the present invention.

[0018] Figure 6This is a diagram showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the phase of the Rayleigh wave in an elastic wave resonator having the same structure as the first and second elastic wave resonators in the first embodiment of the present invention.

[0019] Figure 7 This is a diagram showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the relative bandwidth in an elastic wave resonator having the same structure as the first elastic wave resonator and the second elastic wave resonator in the first embodiment of the present invention.

[0020] Figure 8 This is a graph showing the relationship between the thickness of the portion of the first layer of the first dielectric film located on the first IDT electrode in the first embodiment of the present invention and the phase of the higher-order mode.

[0021] Figure 9 This is a schematic front sectional view showing the vicinity of a pair of electrode fingers of the first elastic wave resonator and the vicinity of a pair of electrode fingers of the second elastic wave resonator in the second embodiment of the present invention.

[0022] Figure 10 This is a diagram showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the phase of the Rayleigh wave in the first and second elastic wave resonators of the second embodiment of the present invention.

[0023] Figure 11 It is Figure 10 A portion of the image is shown in enlarged form.

[0024] Explanation of reference numerals in the attached figures

[0025] 1: Elastic wave resonator;

[0026] 1A, 1B: First elastic wave resonator, second elastic wave resonator;

[0027] 2: Supporting components;

[0028] 3: Support base plate;

[0029] 4, 5: First intermediate layer, second intermediate layer;

[0030] 6A, 6B: First piezoelectric layer, second piezoelectric layer;

[0031] 7: IDT electrode;

[0032] 7A, 7B: First IDT electrode, Second IDT electrode;

[0033] 8: Dielectric film;

[0034] 8A, 8B: First dielectric film, second dielectric film;

[0035] 8a, 8b: Level 1 and Level 2;

[0036] 8c, 8d: Layer 1 and Layer 2;

[0037] 8e, 8f: Layer 1, Layer 2;

[0038] 9A~9D: Reflectors;

[0039] 10: Elastic wave device;

[0040] 16, 17: Busbar 1 and Busbar 2;

[0041] 18, 19: First electrode finger, second electrode finger;

[0042] 20: Elastic wave device;

[0043] 21B: Second elastic wave resonator;

[0044] 101: Elastic wave resonator;

[0045] 107: IDT electrode;

[0046] 108: Dielectric film;

[0047] A: Intersection area. Detailed Implementation

[0048] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0049] In addition, it should be noted that the embodiments described in this specification are illustrative and that partial substitutions or combinations of structures can be made between different embodiments.

[0050] Figure 1 This is a schematic top view of the elastic wave device according to the first embodiment of the present invention. Figure 1 The first dielectric film and the second dielectric film, which will be described later, are omitted in the text.

[0051] The elastic wave device 10 is used as part of a filter device. The elastic wave device 10 has multiple elastic wave resonators. However, the elastic wave device of the present invention can also be a filter device. The structure of the elastic wave device 10 will be described below.

[0052] The elastic wave device 10 has a first elastic wave resonator 1A and a second elastic wave resonator 1B. Alternatively, the elastic wave device 10 only needs to have at least one first elastic wave resonator 1A and at least one second elastic wave resonator 1B.

[0053] The first elastic wave resonator 1A has a first IDT electrode 7A. The first IDT electrode 7A has a pair of busbars and a plurality of electrode fingers. Specifically, the pair of busbars is a first busbar 16 and a second busbar 17. The first busbar 16 and the second busbar 17 are opposite to each other. Specifically, the plurality of electrode fingers is a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19. One end of each of the plurality of first electrode fingers 18 is connected to the first busbar 16. One end of each of the plurality of second electrode fingers 19 is connected to the second busbar 17. The plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interleaved with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials. Hereinafter, the first electrode fingers 18 and the second electrode fingers 19 are sometimes referred to together as electrode fingers.

[0054] The second elastic wave resonator 1B has a second IDT electrode 7B. Like the first IDT electrode 7A, the second IDT electrode 7B also has a pair of busbars and a plurality of electrode fingers. Hereinafter, the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction, and the direction orthogonal to the electrode finger extension direction is defined as the electrode finger orthogonal direction. In the elastic wave device 10, the electrode finger extension directions in the first elastic wave resonator 1A and the electrode finger extension directions in the second elastic wave resonator 1B are parallel. However, the electrode finger extension directions in the first elastic wave resonator 1A and the electrode finger extension directions in the second elastic wave resonator 1B are not necessarily parallel.

[0055] Figure 2 This is a schematic front sectional view showing the vicinity of a pair of electrode fingers of the first elastic wave resonator and the vicinity of a pair of electrode fingers of the second elastic wave resonator in the first embodiment.

[0056] The first elastic wave resonator 1A includes a support member 2, a first piezoelectric layer 6A, a second piezoelectric layer 6B, the aforementioned first IDT electrode 7A, and a first dielectric film 8A. The support member 2 includes a support substrate 3, a first intermediate layer 4, and a second intermediate layer 5. The first intermediate layer 4 is disposed on the support substrate 3. The second intermediate layer 5 is disposed on the first intermediate layer 4. However, the structure of the support member 2 is not limited to the above-described structure. For example, the support member 2 may only include the support substrate 3.

[0057] A first piezoelectric layer 6A is provided on the second intermediate layer 5 of the support member 2. A second piezoelectric layer 6B is provided on the first piezoelectric layer 6A. A first IDT electrode 7A is provided on the second piezoelectric layer 6B. A first dielectric film 8A is provided on the second piezoelectric layer 6B, such that it covers the first IDT electrode 7A. The first IDT electrode 7A is embedded in the first dielectric film 8A. In this specification, "the IDT electrode provided on the piezoelectric layer is embedded in the dielectric film" means that the thickness of the dielectric film is greater than the thickness of the IDT electrode, and the dielectric film is provided on the piezoelectric layer such that it covers the IDT electrode. The thickness of the dielectric film referred to here is the distance in the dielectric film from the surface in contact with the piezoelectric layer to the surface opposite to that surface.

[0058] The second elastic wave resonator 1B shares a support member 2, a first piezoelectric layer 6A, and a second piezoelectric layer 6B with the first elastic wave resonator 1A. Furthermore, the second elastic wave resonator 1B has a second IDT electrode 7B and a second dielectric film 8B. In the second elastic wave resonator 1B, the second IDT electrode 7B is disposed on the second piezoelectric layer 6B. The second dielectric film 8B is disposed on the second piezoelectric layer 6B, covering the second IDT electrode 7B. The second IDT electrode 7B is embedded in the second dielectric film 8B.

[0059] In the first elastic wave resonator 1A, an elastic wave is excited by applying an AC voltage to the first IDT electrode 7A. In the second elastic wave resonator 1B, an elastic wave is excited by applying an AC voltage to the second IDT electrode 7B. In this embodiment, the Rayleigh wave is a useless wave.

[0060] like Figure 2 As shown, a first IDT electrode 7A and a second IDT electrode 7B sandwich a second piezoelectric layer 6B and are positioned opposite each other to the first piezoelectric layer 6A. The distance between the first piezoelectric layer 6A and the first IDT electrode 7A is equal to the thickness of the portion of the second piezoelectric layer 6B in which the first IDT electrode 7A is disposed. The distance between the first piezoelectric layer 6A and the second IDT electrode 7B is equal to the thickness of the portion of the second piezoelectric layer 6B in which the second IDT electrode 7B is disposed. The thicknesses of the portion of the second piezoelectric layer 6B in which the first IDT electrode 7A and the portion in which the second IDT electrode 7B are disposed are different. Therefore, the distances between the first piezoelectric layer 6A and the first IDT electrode 7A, and the distances between the first piezoelectric layer 6A and the second IDT electrode 7B, are different.

[0061] In this embodiment, the second IDT electrode 7B and the second dielectric film 8B are indirectly disposed on the first piezoelectric layer 6A, separated by the second piezoelectric layer 6B. Alternatively, the second IDT electrode 7B may be directly disposed on the first piezoelectric layer 6A. The second dielectric film 8B may also be directly disposed on the first piezoelectric layer 6A, covering the second IDT electrode 7B. In this invention, it is sufficient that the second IDT electrode 7B and the second dielectric film 8B are disposed directly or indirectly on the first piezoelectric layer 6A.

[0062] In the elastic wave device 10, when the wavelength defined by the electrode finger spacing of the first IDT electrode 7A is set as λ1 and the wavelength defined by the electrode finger spacing of the second IDT electrode 7B is set as λ2, λ1 = λ2. The electrode finger spacing is the center-to-center distance between adjacent electrode fingers in the orthogonal direction of the electrode fingers. However, in this invention, λ1 ≠ λ2. Alternatively, for example, when the elastic wave device 10 has multiple first elastic wave resonators 1A, the wavelength λ1 may be different between the multiple first elastic wave resonators 1A. When the elastic wave device 10 has multiple second elastic wave resonators 1B, the wavelength λ2 may be different between the multiple second elastic wave resonators 1B.

[0063] The first IDT electrode 7A and the second IDT electrode 7B each comprise multiple metal layers. Both the first IDT electrode 7A and the second IDT electrode 7B comprise a main electrode layer. In this specification, the main electrode layer refers to a metal layer that accounts for more than 50 wt% (i.e., greater than 50 wt%) of all the metal layers. Specifically, in the first IDT electrode 7A, starting from the second piezoelectric layer 6B side, a NiCr layer, a Pt layer, a Ti layer, an Al layer, and a Ti layer are sequentially stacked. The main electrode layer of the first IDT electrode 7A is a Pt layer. The stacking structure and main electrode layer of the second IDT electrode 7B are also the same as those of the first IDT electrode 7A.

[0064] Furthermore, the stacked structure and main electrode layer of the first IDT electrode 7A and the second IDT electrode 7B are not limited to the aforementioned stacked structure and main electrode layer. The first IDT electrode 7A and the second IDT electrode 7B only need to each contain at least one metal layer.

[0065] Return to Figure 1When viewed from the orthogonal direction of the electrode fingers, the region where adjacent electrode fingers of the first IDT electrode 7A overlap with each other is the intersection region A of the first elastic wave resonator 1A. This intersection region A is defined based on the structure of the first IDT electrode 7A, the region of the first piezoelectric layer 6A, and the region of the second piezoelectric layer 6B. On the other hand, when viewed from the orthogonal direction of the electrode fingers, the region where adjacent electrode fingers of the second IDT electrode 7B overlap with each other is the intersection region of the second elastic wave resonator 1B. This intersection region is defined based on the structure of the second IDT electrode 7B, the region of the first piezoelectric layer 6A, and the region of the second piezoelectric layer 6B.

[0066] When the dimension of the cross region along the extension direction of the electrode fingers is defined as the cross width, the cross width in the first elastic wave resonator 1A and the cross width in the second elastic wave resonator 1B are the same. Alternatively, the cross widths may differ between the multiple elastic wave resonators of the elastic wave device 10.

[0067] The first elastic wave resonator 1A has a pair of reflectors. Specifically, the pair of reflectors of the first elastic wave resonator 1A is reflector 9A and reflector 9B. Reflectors 9A and 9B are positioned opposite each other, sandwiching the first IDT electrode 7A. Similarly, the second elastic wave resonator 1B has a pair of reflectors. Specifically, the pair of reflectors of the second elastic wave resonator 1B is reflector 9C and reflector 9D. Reflectors 9C and 9D are positioned opposite each other, sandwiching the second IDT electrode 7B. Each reflector is disposed on the second piezoelectric layer 6B.

[0068] Reflector 9A has a pair of reflector busbars and multiple reflector electrode fingers. The pair of reflector busbars are opposite each other. One end of each of the multiple reflector electrode fingers is connected to one reflector busbar. The other end of each of the multiple reflector electrode fingers is connected to another reflector busbar. Reflectors 9B, 9C, and 9D are configured in the same way as reflector 9A.

[0069] like Figure 2 As shown, in this embodiment, the first dielectric film 8A and the second dielectric film 8B are laminated films. Specifically, the first dielectric film 8A includes a first layer 8a and a second layer 8b. The first layer 8a is disposed on the second piezoelectric layer 6B. The second layer 8b is disposed on the first layer 8a. The first IDT electrode 7A is embedded in the first layer 8a. On the other hand, the second dielectric film 8B includes a first layer 8c and a second layer 8d. The first layer 8c is disposed on the second piezoelectric layer 6B. The second layer 8d is disposed on the first layer 8c. The second IDT electrode 7B is embedded in the first layer 8c.

[0070] The first dielectric film 8A and the second dielectric film 8B are integrally formed using the same material. Specifically, the first layer 8a of the first dielectric film 8A and the first layer 8c of the second dielectric film 8B are integrally formed using the same material. Similarly, the second layer 8b of the first dielectric film 8A and the second layer 8d of the second dielectric film 8B are also integrally formed using the same material.

[0071] More specifically, silicon oxide is used as the material for the first layer 8a of the first dielectric film 8A and the first layer 8c of the second dielectric film 8B. Silicon nitride is used as the material for the second layer 8b of the first dielectric film 8A and the second layer 8d of the second dielectric film 8B. However, the materials of each layer in the first dielectric film 8A and the second dielectric film 8B are not limited to the above-mentioned materials. Alternatively, the first dielectric film 8A and the second dielectric film 8B may each be a single-layer dielectric film.

[0072] The portion of the dielectric film in which the first dielectric film 8A and the second dielectric film 8B are integrally formed, covering the first IDT electrode 7A, is the first dielectric film 8A. The portion of the aforementioned dielectric film covering the second IDT electrode 7B is the second dielectric film 8B. Alternatively, the first dielectric film 8A and the second dielectric film 8B can also be provided separately.

[0073] In this embodiment, the material combination of the support substrate 3, the first intermediate layer 4, the second intermediate layer 5, the first piezoelectric layer 6A, and the second piezoelectric layer 6B, which are the laminates, is silicon / silicon nitride / silicon oxide / lithium niobate / lithium niobate. However, the materials of the support substrate 3, the first intermediate layer 4, the second intermediate layer 5, the first piezoelectric layer 6A, and the second piezoelectric layer 6B are not limited to the above-mentioned materials.

[0074] The polarization directions of the first piezoelectric layer 6A and the second piezoelectric layer 6B are different from each other. More specifically, in this embodiment, the polarization directions of the first piezoelectric layer 6A and the second piezoelectric layer 6B are reversed.

[0075] Here, in any Euler angle (φ, θ, ψ), angle φ is the first Euler angle, angle θ is the second Euler angle, and angle ψ is the third Euler angle. In this specification, the reversal of polarization directions in two piezoelectric layers means that the difference between the second Euler angles θ in the two piezoelectric layers is within the range of 180° ± 5°. Hereinafter, the Euler angles of the first piezoelectric layer 6A are defined as (φ1, θ1, ψ1), and the Euler angles of the second piezoelectric layer 6B are defined as (φ2, θ2, ψ2). The difference between angle θ1, which is the second Euler angle in the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A, and angle θ2, which is the second Euler angle in the Euler angles (φ2, θ2, ψ2) of the second piezoelectric layer 6B, is within the range of 180° ± 5°. Furthermore, the difference between the second Euler angle θ1 and the second Euler angle θ2 is not limited to the above.

[0076] This embodiment is characterized by the following structure: 1) The distance between the first piezoelectric layer 6A and the first IDT electrode 7A and the distance between the first piezoelectric layer 6A and the second IDT electrode 7B are different from each other. 2) The polarization direction of the first piezoelectric layer 6A and the polarization direction of the second piezoelectric layer 6B are different from each other. 3) The first IDT electrode 7A is embedded in the first dielectric film 8A, and the second IDT electrode 7B is embedded in the second dielectric film 8B. Therefore, unwanted waves in the first elastic wave resonator 1A and the second elastic wave resonator 1B, which are multiple elastic wave resonators, can be suppressed. Hereinafter, details will be explained with reference to the elastic wave resonator of the comparative example.

[0077] like Figure 3 As shown, the difference between the comparative example elastic wave resonator 101 and the first elastic wave resonator 1A in the first embodiment is that the IDT electrode 107 is not embedded in the dielectric film 108. Another difference between the comparative example elastic wave resonator 101 and the first elastic wave resonator 1A in the first embodiment is that the dielectric film 108 is a single-layer dielectric film.

[0078] Specifically, in the comparative example of the elastic wave resonator 101, similar to the first embodiment, a support member 2, a first piezoelectric layer 6A, and a second piezoelectric layer 6B are stacked. However, unlike the first embodiment, in the comparative example, the thickness of the dielectric film 108 is thinner than the thickness of the IDT electrode 107. Furthermore, the dielectric film 108 is provided on the second piezoelectric layer 6B, covering the IDT electrode 107. That is, the IDT electrode 107 is covered by the dielectric film 108, but not embedded within it.

[0079] In the comparative example of the elastic wave resonator 101, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the phase of the Rayleigh wave (a useless wave) was derived through simulation whenever the thickness of the second piezoelectric layer 6B was varied. In this study, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the second Euler angle θ2 of the second piezoelectric layer 6B was set to θ2 = θ1 - 180°. In this study, the thickness of the second piezoelectric layer 6B in the elastic wave resonator 101 was set to 10 nm, 30 nm, or 50 nm.

[0080] Figure 4 This is a graph showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the phase of the Rayleigh wave in the elastic wave resonator of the comparative example.

[0081] like Figure 4 As shown, in the comparative example, whenever the thickness of the second piezoelectric layer 6B differs by 20 nm, the relationship between the second Euler angle θ1 and the phase of the Rayleigh wave becomes significantly different. Therefore, for example, in the case where multiple elastic wave resonators 101 of the comparative example with different thicknesses of the second piezoelectric layer 6B are provided in the elastic wave device, it is difficult to suppress the Rayleigh wave in all of the elastic wave resonators 101.

[0082] In contrast, in the first embodiment, Rayleigh waves, which are unwanted waves, can be suppressed by both the first elastic wave resonator 1A and the second elastic wave resonator 1B, whose thicknesses are different in the second piezoelectric layer 6B. (Refer to...) Figure 5 The elastic wave resonator 1 shown illustrates this situation. The elastic wave resonator 1 has the same characteristics as... Figure 2 The first elastic wave resonator 1A and the second elastic wave resonator 1B shown have the same structure.

[0083] Specifically, in Figure 5 The elastic wave resonator 1 shown comprises a support substrate 3, a first intermediate layer 4, a second intermediate layer 5, a first piezoelectric layer 6A, and a second piezoelectric layer 6B, stacked sequentially. An IDT electrode 7 is disposed on the second piezoelectric layer 6B. A dielectric film 8 is disposed on the second piezoelectric layer 6B, covering the IDT electrode 7. The dielectric film 8 is a stack of a first layer 8e and a second layer 8f. The IDT electrode 7 is embedded in the first layer 8e. The second layer 8f is disposed on the first layer 8e.

[0084] In the elastic wave resonator 1, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the phase of the Rayleigh wave was derived through simulation whenever the thickness of the second piezoelectric layer 6B was varied. The design parameters of the elastic wave resonator 1 are as follows. In the elastic wave resonator 1, the wavelength defined by the electrode finger spacing is denoted as λ. In this specification, unless otherwise specified, the thickness of the first layer in the dielectric film is the overall thickness of the first layer. However, sometimes the thickness of a portion of the first layer is also used as a parameter, which will be described later.

[0085] Support substrate: material is Si, thickness is 100μm, azimuth angle is (111), Euler angles (φ, θ, ψ) are (-45°, -54.7°, 73°)

[0086] First intermediate layer: made of SiN, with a thickness of 50nm.

[0087] Second intermediate layer: material is SiO2, thickness is 400nm

[0088] The first piezoelectric layer is made of LiNbO3 with a thickness of 300 nm and Euler angles (φ1, θ1, ψ1) of (0°, θ1, 0°). The second Euler angle θ1 is varied in steps of 0.5° within a range of 90° to 160°.

[0089] The second piezoelectric layer is made of LiNbO3. Its thickness is varied in 10nm increments within a range of 10nm to 60nm. The Euler angles (φ2, θ2, ψ2) are (0°, θ2, 0°). The second Euler angle θ2 is set to θ1-180° and varied in 0.5° increments within a range of -90° to -20°.

[0090] IDT electrode: The material from the second piezoelectric layer side is NiCr / Pt / Ti / Al / Ti, and the thickness from the second piezoelectric layer side is 10nm / 30nm / 30nm / 150nm / 10nm, with a duty cycle of 0.5 and 100 electrode pairs.

[0091] Wavelength λ: 1.5μm

[0092] Cross width: 20λ

[0093] The first layer of the dielectric film: the material is SiO2, and the thickness is 330nm.

[0094] The second layer in the dielectric film: the material is SiN, and the thickness is 30nm.

[0095] Figure 6This is a diagram showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the phase of the Rayleigh wave in an elastic wave resonator having the same structure as the first and second elastic wave resonators in the first embodiment.

[0096] like Figure 6 As shown, even with variations in the thickness of the second piezoelectric layer 6B, the second Euler angle θ1 of the first piezoelectric layer 6A, where the phase of the Rayleigh wave reaches a minimum, remains almost unchanged, around 105° to 106°. Strictly speaking, the thicker the second piezoelectric layer 6B, the slightly smaller the second Euler angle θ1 of the first piezoelectric layer 6A, where the phase of the Rayleigh wave reaches a minimum. However, the change in this second Euler angle θ1 is less than 1°. Therefore, in the case where the elastic wave device has multiple elastic wave resonators 1 with varying thicknesses of the second piezoelectric layer 6B, Rayleigh waves, which are unwanted waves, can be suppressed in any one of the elastic wave resonators 1.

[0097] In the first embodiment, the elastic wave resonator 1 with a relatively thick second piezoelectric layer 6B is the first elastic wave resonator 1A. The elastic wave resonator 1 with a relatively thin second piezoelectric layer 6B is the second elastic wave resonator 1B. Based on the above, among the first elastic wave resonator 1A and the second elastic wave resonator 1B, which are multiple elastic wave resonators in the elastic wave device 10, Rayleigh waves, which are useless waves, can be suppressed.

[0098] Furthermore, by adjusting the thickness of the first dielectric film 8A, the resonant frequency of the first elastic wave resonator 1A can be adjusted. Similarly, by adjusting the thickness of the second dielectric film 8B, the resonant frequency of the second elastic wave resonator 1B can be adjusted. The thicknesses of the first dielectric film 8A and the second dielectric film 8B can also be different. In this case, the resonant frequencies of the first elastic wave resonator 1A and the second elastic wave resonator 1B can be adjusted separately.

[0099] As described above, the thickness of the second piezoelectric layer 6B differs between the first elastic wave resonator 1A and the second elastic wave resonator 1B. Consequently, the relative bandwidth differs between the first elastic wave resonator 1A and the second elastic wave resonator 1B. When the resonant frequency is set to fr and the anti-resonant frequency is set to fa, the relative bandwidth is expressed as (|fa-fr| / fr)×100[%]. For example, when the elastic wave device 10 is used as a filter device, the thickness of the second piezoelectric layer 6B can be adjusted according to the resonant frequency or anti-resonant frequency of the first elastic wave resonator 1A, thereby adjusting the relative bandwidth. The same applies to the second elastic wave resonator 1B. (Refer to...) Figure 5 The elastic wave resonator 1 shown is used to illustrate that the relative bandwidth can be adjusted in the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0100] In the elastic wave resonator 1, the relationship between the second Euler angle θ1 and the relative bandwidth of the first piezoelectric layer 6A was derived through simulation when the thickness of the second piezoelectric layer 6B was varied. The design parameters of the elastic wave resonator 1 were set as follows: Figure 6 The design parameters of the elastic wave resonator 1 in the study shown are the same.

[0101] Figure 7 This is a diagram showing the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the relative bandwidth in an elastic wave resonator having the same structure as the first and second elastic wave resonators in the first embodiment.

[0102] like Figure 7 As shown, the thicker the second piezoelectric layer 6B, the smaller the relative bandwidth becomes. Therefore, by adjusting the thickness of the second piezoelectric layer 6B in the elastic wave resonator 1, the relative bandwidth in the elastic wave resonator 1 can be adjusted. On the other hand, even if the second Euler angle θ1 of the first piezoelectric layer 6A changes, the relative bandwidth remains almost unchanged.

[0103] In the first elastic wave resonator 1A and the second elastic wave resonator 1B, which have the same structure as the elastic wave resonator 1, the relative bandwidth can also be adjusted by adjusting the thickness of the second piezoelectric layer 6B.

[0104] For example, when the elastic wave device 10 is used in a filter device, if the resonant frequency or anti-resonant frequency of the first elastic wave resonator 1A is close to the frequency at the end of the passband of the filter device, the relative bandwidth of the first elastic wave resonator 1A can be narrowed. In this case, the steepness can be improved. In this specification, "high steepness" means that near the end of the passband, the change in frequency is small relative to a certain fixed attenuation.

[0105] On the other hand, when the resonant frequency or anti-resonant frequency of the second elastic wave resonator 1B is far from the end of the passband of the filter device, the relative bandwidth of the second elastic wave resonator 1B can be widened. This makes it easier to reduce insertion loss in the passband. In this way, the filter characteristics of the filter device using the elastic wave device 10 can be improved. Furthermore, unwanted waves can be suppressed in both the first elastic wave resonator 1A and the second elastic wave resonator 1B. Therefore, the filter characteristics of the filter device can be further improved.

[0106] As in the first embodiment, silicon oxide is preferably used as the material for the first layer 8a and the first layer 8c of the first dielectric film 8A and the second dielectric film 8B. In this case, the first IDT electrode 7A and the second IDT electrode 7B are embedded in the layer where silicon oxide is used as the material. This reduces the absolute value of the temperature coefficient of frequency (TCF) in the first elastic wave resonator 1A and the second elastic wave resonator 1B. Consequently, the temperature characteristics of the frequency in the first elastic wave resonator 1A and the second elastic wave resonator 1B are improved.

[0107] Silicon nitride is preferably used as the material for the second layer 8b and the second layer 8d in the first dielectric film 8A and the second dielectric film 8B. This improves the moisture resistance of the elastic wave device 10.

[0108] The inventors of this invention discovered that the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, can be calculated based on the thickness of the second piezoelectric layer 6B and the thickness of the main electrode layer in the first IDT electrode 7A. More specifically, the design parameters of the first elastic wave resonator 1A were set as follows, and simulations were performed. From this, Equation 1 was derived, which is a relationship between the second Euler angle θ1 of the first piezoelectric layer 6A that can suppress Rayleigh waves, the thickness of the second piezoelectric layer 6B, and the thickness of the main electrode layer in the first IDT electrode 7A.

[0109] Support substrate: material is Si, thickness is 100μm, azimuth angle is (111), Euler angles (φ, θ, ψ) are (-45°, -54.7°, 73°)

[0110] First intermediate layer: made of SiN, with a thickness of 50nm.

[0111] Second intermediate layer: material is SiO2, thickness is 400nm

[0112] The first piezoelectric layer is made of LiNbO3 with a thickness of 300 nm and Euler angles (φ1, θ1, ψ1) of (0°, θ1, 0°). The second Euler angle θ1 is varied within a range of 90° to 110°.

[0113] The second piezoelectric layer is made of LiNbO3 with a thickness of 10nm, 30nm, or 50nm. The Euler angles (φ2, θ2, ψ2) are (0°, θ2, 0°). The second Euler angle θ2 is set to θ1-180° and varies within the range of -90° to -70°.

[0114] The first IDT electrode: the material from the second piezoelectric layer side is NiCr / Pt / Ti / Al / Ti, the thickness from the second piezoelectric layer side is 10nm / 10nm, 30nm, or 50nm / 30nm / 150nm / 10nm, the duty cycle is 0.5, and the number of electrode pairs is 100.

[0115] Wavelength λ1: 1μm

[0116] Cross width: 20λ1

[0117] The first layer of the first dielectric film: the material is SiO2, and the thickness is 330 nm.

[0118] The second layer in the first dielectric film: the material is SiN, and the thickness is 30nm.

[0119] In Equation 1 below, the thickness of the main electrode layer in the first IDT electrode 7A is set as t_IDT[μm], and the thickness of the portion of the second piezoelectric layer 6B in which the first IDT electrode 7A is disposed is set as t_piezo[μm]. Theta[°], expressed as an angle in Equation 1, is the second Euler angle θ1 of the first piezoelectric layer 6A that can suppress Rayleigh waves.

[0120] [Mathematical Expression 1]

[0121] …Formula 1

[0122] When the Euler angles (φ1, θ1, ψ1) in the first piezoelectric layer 6A are (0°, θ1, 0°), the second Euler angle θ1 is made to be the angle Theta in Equation 1, thereby effectively suppressing Rayleigh waves in the first elastic wave resonator 1A.

[0123] In Equation 1, the angle Theta depends on the thickness of the second piezoelectric layer 6B. Furthermore, the thickness of the second piezoelectric layer 6B differs between the first elastic wave resonator 1A and the second elastic wave resonator 1B. However, even with variations in the thickness of the second piezoelectric layer 6B, the angle Theta does not change significantly. This is clearly because, as... Figure 6 as well as Figure 7 As shown, even if the thickness of the second piezoelectric layer 6B changes, the second Euler angle θ1, which suppresses Rayleigh waves, does not change significantly. Therefore, by setting the Euler angle (φ1, θ1, ψ1) of the first piezoelectric layer 6A to (0°, θ1, 0°) and the second Euler angle θ1 to the angle Theta, Rayleigh waves can be effectively suppressed in both the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0124] Further research has clarified that when the first Euler angle φ1 is within the range of 0°±5° and the third Euler angle ψ1 is within the range of 0°±5°, the same effect as described above can be obtained as long as the second Euler angle θ1 is within the range of Theta±10°. Based on the above, preferably, the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A are within the range of 0°±5°, and θ1 is within the range of 0°±5°, and the second Euler angle θ1 is within the range of Theta±10°. Therefore, Rayleigh waves can be effectively suppressed in both the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0125] In the first embodiment, lithium niobate is used as the material for both the first piezoelectric layer 6A and the second piezoelectric layer 6B. Furthermore, even when lithium tantalate is used as the material for both the first and second piezoelectric layers 6A, it is preferable that the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A are within the aforementioned range. That is, preferably, the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A are within the range of 0°±5°, and θ1 is within the range of 0°±5°, and the second Euler angle θ1 is within the range of Theta±10°. In this case, Rayleigh waves can be effectively suppressed in both the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0126] The following, such as Figure 2 As shown, the thickness of the portion of the layer in the first dielectric film 8A covering the first IDT electrode 7A located on the first IDT electrode 7A is set to t_d1. In the first embodiment, the layer in the first dielectric film 8A covering the first IDT electrode 7A is the first layer 8a. Preferably, the thickness t_d1 of the first layer 8a is 0.25λ1 or less. This allows for the suppression of higher-order modes in the first elastic wave resonator 1A. Details are shown below.

[0127] The design parameters of the first elastic wave resonator 1A were set as follows, and simulations were performed. From this, the range of the thickness t_d1 of the first layer 8a in the first dielectric film 8A, which can suppress higher-order modes, was derived.

[0128] Support substrate: material is Si, thickness is 100μm, azimuth angle is (111), Euler angles (φ, θ, ψ) are (-45°, -54.7°, 73°)

[0129] First intermediate layer: made of SiN, with a thickness of 50nm.

[0130] Second intermediate layer: material is SiO2, thickness is 400nm

[0131] First piezoelectric layer: material is LiNbO3, thickness is 300nm, Euler angles (φ1, θ1, ψ1) are (0°, 105°, 0°)

[0132] The second piezoelectric layer is made of LiNbO3 with a thickness of 10 nm and Euler angles (φ2, θ2, ψ2) of (0°, -75°, 0°).

[0133] The first IDT electrode: the material from the second piezoelectric layer side is NiCr / Pt / Ti / Al / Ti, the thickness from the second piezoelectric layer side is 10nm / 30nm / 30nm / 150nm / 10nm, the duty cycle is 0.5, and the number of electrode pairs is 100.

[0134] Wavelength λ1: 1.5μm

[0135] Cross width: 20λ1

[0136] The first layer of the first dielectric film is made of SiO2. Regarding the thickness t_d1, it varies in 100nm increments within a range of 100nm to 1000nm. If calculated based on wavelength λ1, it varies in 0.067λ1 increments within a range of 0.067λ1 to 0.667λ1. Regarding the overall thickness, it varies in 100nm increments within a range of 330nm to 1230nm.

[0137] The second layer in the first dielectric film: the material is SiN, and the thickness is 30nm.

[0138] Figure 8 This is a graph showing the relationship between the thickness of the portion of the first layer of the first dielectric film in the first embodiment located on the first IDT electrode and the phase of the higher-order mode.

[0139] like Figure 8 As shown, when the thickness t_d1 of the first layer 8a in the first dielectric film 8A is thicker than 0.25λ1, the suppression of higher-order modes in the first elastic wave resonator 1A is insufficient. In contrast, it is known that when the thickness t_d1 of the first layer 8a is 0.25λ1 or less, higher-order modes can be suppressed. Furthermore, it is more preferable that the thickness t_d1 of the first layer 8a is 0.2λ1 or less. Thus, higher-order modes can be further suppressed in the first elastic wave resonator 1A.

[0140] Similarly, in the second elastic wave resonator 1B, when the thickness of the portion of the layer in the second dielectric film 8B covering the second IDT electrode 7B located on the second IDT electrode 7B is set to t_d2, it is preferable that the thickness t_d2 is 0.25λ2 or less. Specifically, in the first embodiment, the layer in the second dielectric film 8B covering the second IDT electrode 7B is the first layer 8c. Therefore, it is preferable that the thickness t_d2 of the first layer 8c is 0.25λ2 or less. As a result, higher-order modes can be suppressed in the second elastic wave resonator 1B. More preferably, the thickness t_d2 of the first layer 8c is 0.2λ2 or less. As a result, higher-order modes can be further suppressed in the second elastic wave resonator 1B.

[0141] When the elastic wave device 10 has multiple first elastic wave resonators 1A, in each first elastic wave resonator 1A, the thickness t_d1 of the first layer 8a in the first dielectric film 8A only needs to be calculated based on the wavelength λ1. In this case, it is preferable that the thickness t_d1 of the first layer 8a is 0.25λ1 or less in at least one first elastic wave resonator 1A, more preferably 0.2λ1 or less. This allows higher-order modes to be suppressed in at least one first elastic wave resonator 1A. More preferably, the thickness t_d1 of the first layer 8a is 0.25λ1 or less in all first elastic wave resonators 1A, even more preferably 0.2λ1 or less. This allows higher-order modes to be suppressed in all first elastic wave resonators 1A.

[0142] The same applies when the elastic wave device 10 has multiple second elastic wave resonators 1B. Specifically, in each second elastic wave resonator 1B, the thickness t_d2 of the first layer 8c in the second dielectric film 8B only needs to be calculated based on the wavelength λ2. In this case, it is preferable that the thickness t_d2 of the first layer 8c is 0.25λ2 or less in at least one second elastic wave resonator 1B, more preferably 0.2λ2 or less. This allows higher-order modes to be suppressed in at least one second elastic wave resonator 1B. More preferably, the thickness t_d2 of the first layer 8c is 0.25λ2 or less in all second elastic wave resonators 1B, even more preferably 0.2λ2 or less. This allows higher-order modes to be suppressed in all second elastic wave resonators 1B.

[0143] The following examples illustrate the materials of each layer of the support member 2, the first piezoelectric layer 6A, and the second piezoelectric layer 6B. In this specification, the term "main component" refers to a component that accounts for more than 50 wt% of the component. The material of the aforementioned main component may exist in any of the following states: single crystal, polycrystalline, and amorphous, or a mixture thereof.

[0144] As the material for the support substrate 3, for example, aluminum nitride, lithium tantalate, lithium niobate, piezoelectric materials such as quartz, bauxite, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, forsterite, spinel, siliconium, ceramics such as siliconium oxide, alumina, silicon oxynitride, DLC (diamond-like carbon), diamond, dielectrics such as diamond, or semiconductors such as silicon, or materials with the above materials as the main component can also be used. The spinel contains an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of the spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4. The same applies to the spinels listed later as examples of materials for the first intermediate layer 4. In the first embodiment, the support substrate 3 is a silicon support substrate.

[0145] In the first embodiment, the first intermediate layer 4 is a hypersonic film. A hypersonic film is a film in which the speed of sound propagating from a bulk wave is relatively high. More specifically, the speed of sound propagating from a hypersonic film is higher than the speed of sound propagating from an elastic wave propagating from the first piezoelectric layer 6A and the second piezoelectric layer 6B. Materials used for the hypersonic film (i.e., the first intermediate layer 4) include, for example, ceramics such as aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, forsterite, spinel, siliconium, alumina, silicon oxynitride, DLC (diamond-like carbon), diamond, or semiconductors such as silicon, or materials primarily composed of the above materials. In the first embodiment, the first intermediate layer 4 is a silicon nitride layer.

[0146] On the other hand, the second intermediate layer 5 is a low-velocity sound film. A low-velocity sound film is a film in which the speed of sound propagating from a bulk wave is relatively low. More specifically, the speed of sound propagating from a low-velocity sound film is lower than the speed of sound propagating from the first piezoelectric layer 6A and the second piezoelectric layer 6B. As the material for the low-velocity sound film (i.e., the second intermediate layer 5), for example, dielectric materials such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds of silicon oxide with added fluorine, carbon, or boron, or materials mainly composed of the above materials, can be used. In the first embodiment, the second intermediate layer 5 is a silicon oxide layer.

[0147] For example, lithium tantalate or lithium niobate can be used as the materials for the first piezoelectric layer 6A and the second piezoelectric layer 6B. In the first embodiment, both the first piezoelectric layer 6A and the second piezoelectric layer 6B are lithium niobate layers. Moreover, the polarization directions of the first piezoelectric layer 6A and the second piezoelectric layer 6B are different from each other.

[0148] In the elastic wave device 10, a first intermediate layer 4 serving as a high-velocity sound membrane, a second intermediate layer 5 serving as a low-velocity sound membrane, a first piezoelectric layer 6A, and a second piezoelectric layer 6B are sequentially stacked. This effectively confines the energy of the elastic wave to the sides of the first piezoelectric layer 6A and the second piezoelectric layer 6B. Furthermore, the support member 2 does not necessarily need to include the first intermediate layer 4 and the second intermediate layer 5.

[0149] In the first embodiment, all the elastic wave resonators in the elastic wave device 10 share the second piezoelectric layer 6B. Alternatively, some of the elastic wave resonators in the elastic wave device 10 may not have the second piezoelectric layer 6B. This example is shown in the second embodiment.

[0150] Figure 9 This is a schematic front sectional view showing the vicinity of a pair of electrode fingers of the first elastic wave resonator and the vicinity of a pair of electrode fingers of the second elastic wave resonator in the second embodiment.

[0151] The difference between this embodiment and the first embodiment is that the second elastic wave resonator 21B does not have a second piezoelectric layer 6B. Apart from the aspects described above, the elastic wave device 20 of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0152] The second elastic wave resonator 21B shares the support member 2 and the first piezoelectric layer 6A with the first elastic wave resonator 1A. However, the second elastic wave resonator 21B does not share the second piezoelectric layer 6B with the first elastic wave resonator 1A. Furthermore, the second elastic wave resonator 21B has a second IDT electrode 7B and a second dielectric film 8B. In the second elastic wave resonator 21B, the second IDT electrode 7B is directly disposed on the first piezoelectric layer 6A. The second dielectric film 8B is directly disposed on the first piezoelectric layer 6A, covering the second IDT electrode 7B. The second IDT electrode 7B is embedded in the second dielectric film 8B.

[0153] In the second elastic wave resonator 21B, the distance between the second IDT electrode 7B and the first piezoelectric layer 6A is 0. On the other hand, in the first elastic wave resonator 1A, the first IDT electrode 7A is indirectly disposed on the first piezoelectric layer 6A, separated by the second piezoelectric layer 6B. Therefore, the value of the distance between the first IDT electrode 7A and the first piezoelectric layer 6A is the same as the value of the thickness of the second piezoelectric layer 6B. Thus, the distance between the first piezoelectric layer 6A and the first IDT electrode 7A and the distance between the first piezoelectric layer 6A and the second IDT electrode 7B are different from each other.

[0154] In this embodiment, the plurality of elastic wave resonators in the elastic wave device 20 includes a first elastic wave resonator 1A having a second piezoelectric layer 6B and a second elastic wave resonator 21B not having a second piezoelectric layer 6B. In this case, Rayleigh waves, which are unwanted waves, can also be suppressed in the plurality of elastic wave resonators of the elastic wave device 20. This case is illustrated below.

[0155] In the first elastic wave resonator 1A, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the phase of the Rayleigh wave was derived through simulation when the thickness of the second piezoelectric layer 6B was varied. Similarly, in the second elastic wave resonator 21B, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the phase of the Rayleigh wave was also derived through simulation. The design parameters of the first elastic wave resonator 1A are as follows.

[0156] Support substrate: material is Si, thickness is 100μm, azimuth angle is (111), Euler angles (φ, θ, ψ) are (-45°, -54.7°, 73°)

[0157] First intermediate layer: made of SiN, with a thickness of 50nm.

[0158] Second intermediate layer: material is SiO2, thickness is 400nm

[0159] The first piezoelectric layer is made of LiNbO3 with a thickness of 300 nm and Euler angles (φ1, θ1, ψ1) of (0°, θ1, 0°). The second Euler angle θ1 is varied in steps of 0.5° within a range of 90° to 160°.

[0160] The second piezoelectric layer is made of LiNbO3. Its thickness is varied in 10nm increments within a range of 10nm to 60nm. The Euler angles (φ2, θ2, ψ2) are (0°, θ2, 0°). The second Euler angle θ2 is set to θ1-180° and varied in 0.5° increments within a range of -90° to -20°.

[0161] The first IDT electrode: the material from the second piezoelectric layer side is NiCr / Pt / Ti / Al / Ti, the thickness from the second piezoelectric layer side is 10nm / 30nm / 30nm / 150nm / 10nm, the duty cycle is 0.5, and the number of electrode pairs is 100.

[0162] Wavelength λ1: 1.3μm

[0163] Cross width: 20λ1

[0164] The first layer of the first dielectric film: the material is SiO2, and the thickness is 330 nm.

[0165] The second layer in the first dielectric film: the material is SiN, and the thickness is 30nm.

[0166] The design parameters of the second elastic wave resonator 21B are set to be the same as those of the first elastic wave resonator 1A, except that the thickness of the second piezoelectric layer 6B is 0 (i.e., the second piezoelectric layer 6B is not provided).

[0167] Figure 10 This is a diagram showing the relationship between the thickness of the second piezoelectric layer in the first elastic wave resonator and the second elastic wave resonator in the second embodiment, the second Euler angle of the first piezoelectric layer, and the phase of the Rayleigh wave. Figure 11 It is Figure 10 A portion of the image is shown in enlarged form.

[0168] like Figure 10 as well as Figure 11 As shown, regardless of whether the thickness of the second piezoelectric layer 6B is not zero or the thickness of the second piezoelectric layer 6B is zero, the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, remains almost unchanged. Therefore, between the first elastic wave resonator 1A with the second piezoelectric layer 6B and the second elastic wave resonator 21B without the second piezoelectric layer 6B, the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, remains almost unchanged. Therefore, Rayleigh waves, which are unwanted waves, can be suppressed in the first elastic wave resonator 1A and the second elastic wave resonator 21B, which are multiple elastic wave resonators in the elastic wave device 20.

Claims

1. An elastic wave device, wherein, It has at least one first elastic wave resonator and at least one second elastic wave resonator. The first elastic wave resonator has: First piezoelectric layer; A second piezoelectric layer is disposed on the first piezoelectric layer; The first IDT electrode is disposed on the second piezoelectric layer and has multiple electrode fingers; as well as A first dielectric film is disposed on the second piezoelectric layer, thereby covering the first IDT electrode. The second elastic wave resonator is an elastic wave resonator that shares the first piezoelectric layer with the first elastic wave resonator, and has the following characteristics: The second IDT electrode is disposed directly or indirectly on the first piezoelectric layer and has multiple electrode fingers; and A second dielectric film is disposed directly or indirectly on the first piezoelectric layer, thereby covering the second IDT electrode. The distance between the first piezoelectric layer and the first IDT electrode and the distance between the first piezoelectric layer and the second IDT electrode are different from each other. The polarization directions of the first piezoelectric layer and the second piezoelectric layer are different from each other. The first IDT electrode is embedded in the first dielectric film, and the second IDT electrode is embedded in the second dielectric film.

2. The elastic wave device according to claim 1, wherein, The second elastic wave resonator shares the second piezoelectric layer with the first elastic wave resonator. The second IDT electrode and the second dielectric film are disposed on the second piezoelectric layer. In the second piezoelectric layer, the thickness of the portion where the first IDT electrode is disposed is different from the thickness of the portion where the second IDT electrode is disposed.

3. The elastic wave device according to claim 1, wherein, The second IDT electrode is directly disposed on the first piezoelectric layer. The second dielectric film is directly disposed on the first piezoelectric layer, thereby covering the second IDT electrode.

4. The elastic wave device according to any one of claims 1 to 3, wherein, When the Euler angles of the first piezoelectric layer are set to (φ1, θ1, ψ1) and the Euler angles of the second piezoelectric layer are set to (φ2, θ2, ψ2), the difference between angle θ1 in the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer and angle θ2 in the Euler angles (φ2, θ2, ψ2) of the second piezoelectric layer is within the range of 180°±5°.

5. The elastic wave device according to any one of claims 1 to 4, wherein, Lithium niobate or lithium tantalate was used as the material for the first piezoelectric layer.

6. The elastic wave device according to claim 5, wherein, The first IDT electrode has at least one metal layer, and the first IDT electrode comprises more than 50 wt% of the main electrode layer in all of the metal layers. When the Euler angle of the first piezoelectric layer is set to (φ1, θ1, ψ1), the Euler angle (φ1, θ1, ψ1) of the first piezoelectric layer is (within the range of 0°±5°, and θ1 is within the range of 0°±5°). When the thickness of the main electrode layer in the first IDT electrode is set as t_IDT[μm], the thickness of the portion of the second piezoelectric layer in which the first IDT electrode is disposed is set as t_piezo[μm], and the angle represented by Equation 1 below is set as Theta[°], the angle θ1 in the Euler angles of the first piezoelectric layer (within the range of 0°±5°, θ1 within the range of 0°±5°) is within the range of Theta±10°. [Mathematical Expression 1] …Formula 1.

7. The elastic wave device according to any one of claims 1 to 6, wherein, When the wavelength defined by the electrode finger spacing in the first IDT electrode is set to λ1, the thickness of the portion of the layer in the first dielectric film covering the first IDT electrode located on the first IDT electrode is 0.25λ1 or less.

8. The elastic wave device according to any one of claims 1 to 7, wherein, The first dielectric film includes a layer using silicon oxide as the material, into which the first IDT electrode is embedded.

9. The elastic wave device according to any one of claims 1 to 8, wherein, The first dielectric film and the second dielectric film are integrally formed using the same material.

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