Elastic wave apparatus

Abstract

To provide an elastic wave apparatus capable of suppressing unwanted waves in multiple elastic wave resonators. [Solution] The elastic wave apparatus 10 of the present invention comprises at least one first elastic wave resonator 1A having a first piezoelectric layer 6A, a second piezoelectric layer 6B, a first IDT electrode 7A, and a first dielectric film 8A, and at least one second elastic wave resonator 1B sharing the first piezoelectric layer 6A with the first elastic wave resonator 1A, and having a second IDT electrode 7B and a second dielectric film 8B. The distance between the first piezoelectric layer 6A and the first IDT electrode 7A is different from the distance between the first piezoelectric layer 6A and the second IDT electrode 7B. The polarization direction of the first piezoelectric layer 6A is different from the polarization direction of the second piezoelectric layer 6B. 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.

Description

Technical Field

[0001] The present invention relates to an elastic wave device.

Background Art

[0002] Conventionally, elastic wave devices have been widely used in filters for mobile phones and the like. In the following Patent Document 1, a plurality of examples of elastic wave devices are disclosed. 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 the laminate. In the elastic wave device cited as a comparative example, a single piezoelectric film is provided on a support member. An IDT electrode is provided on the piezoelectric film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present inventor has found that an elastic wave resonator including a single piezoelectric film and an elastic wave resonator including two piezoelectric films can be used in the same filter device. However, the present inventor has further found that since the cut angles of the piezoelectric films capable of suppressing unnecessary waves are different from each other in both elastic wave resonators, it is difficult to suppress unnecessary waves when both elastic wave resonators are used in one filter device. The present inventor has found that even when the thicknesses of the piezoelectric films are made different from each other among a plurality of elastic wave resonators including two piezoelectric films, the cut angles of the piezoelectric films capable of suppressing unnecessary waves are different from each other among the plurality of elastic wave resonators. Therefore, it is also difficult to suppress unnecessary waves when the plurality of elastic wave resonators are used in one filter device.

[0005] The object of the present invention is to provide an elastic wave apparatus that can suppress unwanted waves in multiple elastic wave resonators. [Means for solving the problem]

[0006] The elastic wave apparatus according to the present invention comprises at least one first elastic wave resonator having a first piezoelectric layer, a second piezoelectric layer provided on the first piezoelectric layer, a first IDT electrode provided on the second piezoelectric layer and having a plurality of electrode fingers, and a first dielectric film provided on the second piezoelectric layer so as to cover the first IDT electrode, and at least one elastic wave resonator sharing the first elastic wave resonator and the first piezoelectric layer, the second IDT electrode being provided directly or indirectly on the first piezoelectric layer and having a plurality of electrode fingers The device comprises at least one second elastic wave resonator having a T electrode and a second dielectric film provided directly or indirectly on the first piezoelectric layer so as to cover the second IDT electrode, wherein 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 polarization direction of the first piezoelectric layer is different from the polarization direction of the second piezoelectric layer, the first IDT electrode is embedded in the first dielectric film, and the second IDT electrode is embedded in the second dielectric film. [Effects of the Invention]

[0007] According to the elastic wave apparatus of the present invention, unwanted waves in multiple elastic wave resonators can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic plan view of an elastic wave apparatus according to the first embodiment of the present invention. [Figure 2] This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of a first elastic wave resonator and the vicinity of a pair of electrode fingers of a second elastic wave resonator in a first embodiment of the present invention. [Figure 3]This is a schematic front cross-sectional view showing the vicinity of one pair of electrode fingers of a comparative example elastic wave resonator. [Figure 4] This figure shows 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 comparative example elastic wave resonator. [Figure 5] This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of an elastic wave resonator having a configuration similar to that of the first and second elastic wave resonators in the first embodiment of the present invention. [Figure 6] This figure shows 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 a configuration similar to the first and second elastic wave resonators of the first embodiment of the present invention. [Figure 7] This figure shows the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the specific bandwidth in an elastic wave resonator having a configuration similar to the first and second elastic wave resonators of the first embodiment of the present invention. [Figure 8] This figure shows the relationship between the thickness of the portion of the first layer located on the first IDT electrode and the phase of the higher-order mode in the first dielectric film of the first embodiment of the present invention. [Figure 9] This is a schematic front cross-sectional view showing the vicinity of a pair of electrode fingers of a first elastic wave resonator and the vicinity of a pair of electrode fingers of a second elastic wave resonator in a second embodiment of the present invention. [Figure 10] This figure shows 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 according to a second embodiment of the present invention. [Figure 11] This is a magnified view of a portion of Figure 10. [Modes for carrying out the invention]

[0009] The present invention will be clarified below by describing specific embodiments of the present invention with reference to the drawings.

[0010] It should be noted that the embodiments described herein are illustrative, and that partial substitution or combination of configurations is possible between different embodiments.

[0011] Figure 1 is a schematic plan view of an elastic wave apparatus according to the first embodiment of the present invention. In Figure 1, the first dielectric film and the second dielectric film, which will be described later, are omitted.

[0012] The elastic wave device 10 is used as part of a filter device. The elastic wave device 10 has a plurality of elastic wave resonators. However, the elastic wave device according to the present invention may be a filter device. The configuration of the elastic wave device 10 will be described below.

[0013] The elastic wave apparatus 10 has one first elastic wave resonator 1A and one second elastic wave resonator 1B. However, the elastic wave apparatus 10 only needs to have at least one first elastic wave resonator 1A and at least one second elastic wave resonator 1B.

[0014] 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. The pair of busbars are specifically a first busbar 16 and a second busbar 17. The first busbar 16 and the second busbar 17 face each other. The plurality of electrode fingers are specifically 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 interlocked with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials. Hereafter, the first electrode fingers 18 and the second electrode fingers 19 may be collectively referred to simply as electrode fingers.

[0015] The second elastic wave resonator 1B has a second IDT electrode 7B. Similar to the first IDT electrode 7A, the second IDT electrode 7B also has a pair of bus bars 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 direction in the first elastic wave resonator 1A and the electrode finger extension direction in the second elastic wave resonator 1B are parallel. However, the electrode finger extension direction in the first elastic wave resonator 1A and the electrode finger extension direction in the second elastic wave resonator 1B do not necessarily have to be parallel.

[0016] FIG. 2 is a schematic front cross-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.

[0017] The first elastic wave resonator 1A includes a support member 2, a first piezoelectric layer 6A, a second piezoelectric layer 6B, the 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 provided on the support substrate 3. The second intermediate layer 5 is provided on the first intermediate layer 4. However, the configuration of the support member 2 is not limited to the above. For example, the support member 2 may consist only of the support substrate 3.

[0018] The first piezoelectric layer 6A is provided on the second intermediate layer 5 in the support member 2. The second piezoelectric layer 6B is provided on the first piezoelectric layer 6A. The first IDT electrode 7A is provided on the second piezoelectric layer 6B. The first dielectric film 8A is provided on the second piezoelectric layer 6B so as to cover the first IDT electrode 7A. The first IDT electrode 7A is embedded in the first dielectric film 8A. In this specification, when an IDT electrode provided on a piezoelectric layer is embedded in a dielectric film, it 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 so as to cover the IDT electrode. The thickness of the dielectric film here refers to the distance from the surface in contact with the piezoelectric layer to the surface facing the surface in the dielectric film.

[0019] 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. 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 provided on the second piezoelectric layer 6B. The second dielectric film 8B is provided on the second piezoelectric layer 6B so as to cover the second IDT electrode 7B. The second IDT electrode 7B is embedded in the second dielectric film 8B.

[0020] In the first elastic wave resonator 1A, elastic waves are excited by applying an AC voltage to the first IDT electrode 7A. In the second elastic wave resonator 1B, elastic waves are excited by applying an AC voltage to the second IDT electrode 7B. In this embodiment, Rayleigh waves are unwanted waves.

[0021] As shown in Figure 2, the first IDT electrode 7A and the second IDT electrode 7B and the first piezoelectric layer 6A face each other with the second piezoelectric layer 6B in between. The distance between the first piezoelectric layer 6A and the first IDT electrode 7A is the thickness of the portion of the second piezoelectric layer 6B where the first IDT electrode 7A is provided. The distance between the first piezoelectric layer 6A and the second IDT electrode 7B is the thickness of the portion of the second piezoelectric layer 6B where the second IDT electrode 7B is provided. In the second piezoelectric layer 6B, the thickness of the portion where the first IDT electrode 7A is provided and the thickness of the portion where the second IDT electrode 7B is provided are different. Therefore, the distance between the first piezoelectric layer 6A and the first IDT electrode 7A is different from the distance between the first piezoelectric layer 6A and the second IDT electrode 7B.

[0022] In this embodiment, the second IDT electrode 7B and the second dielectric film 8B are indirectly provided on the first piezoelectric layer 6A via the second piezoelectric layer 6B. Alternatively, the second IDT electrode 7B may be directly provided on the first piezoelectric layer 6A. The second dielectric film 8B may also be directly provided on the first piezoelectric layer 6A so as to cover the second IDT electrode 7B. In this invention, the second IDT electrode 7B and the second dielectric film 8B may be provided directly or indirectly on the first piezoelectric layer 6A.

[0023] In the elastic wave apparatus 10, when λ1 is the wavelength defined by the electrode finger pitch of the first IDT electrode 7A and λ2 is the wavelength defined by the electrode finger pitch of the second IDT electrode 7B, then λ1 = λ2. The electrode finger pitch is the distance between the centers of adjacent electrode fingers in the direction perpendicular to the electrode fingers. However, in the present invention, λ1 ≠ λ2. Alternatively, for example, if the elastic wave apparatus 10 has a plurality of first elastic wave resonators 1A, the wavelengths λ1 may differ among the plurality of first elastic wave resonators 1A. If the elastic wave apparatus 10 has a plurality of second elastic wave resonators 1B, the wavelengths λ2 may differ among the plurality of second elastic wave resonators 1B.

[0024] The first IDT electrode 7A and the second IDT electrode 7B each include multiple metal layers. The first IDT electrode 7A and the second IDT electrode 7B each include a main electrode layer. In this specification, the main electrode layer refers to a metal layer whose proportion in all metal layers exceeds 50 wt%, i.e., more than 50 wt%. Specifically, in the first IDT electrode 7A, a NiCr layer, a Pt layer, a Ti layer, an Al layer, and a Ti layer are stacked in this order from the second piezoelectric layer 6B side. The main electrode layer of the first IDT electrode 7A is a Pt layer. The stacking configuration and main electrode layer of the second IDT electrode 7B are the same as those of the first IDT electrode 7A.

[0025] The lamination configuration and main electrode layers of the first IDT electrode 7A and the second IDT electrode 7B are not limited to those described above. The first IDT electrode 7A and the second IDT electrode 7B each only need to include at least one metal layer.

[0026] Returning to Figure 1, when viewed from the direction perpendicular to the electrode fingers, the region where adjacent electrode fingers of the first IDT electrode 7A overlap is the crossover region A of the first elastic wave resonator 1A. This crossover region A is defined based on the configuration of the first IDT electrode 7A and comprises the regions of the first piezoelectric layer 6A and the second piezoelectric layer 6B. On the other hand, when viewed from the direction perpendicular to the electrode fingers, the region where adjacent electrode fingers of the second IDT electrode 7B overlap is the crossover region of the second elastic wave resonator 1B. This crossover region is defined based on the configuration of the second IDT electrode 7B and comprises the regions of the first piezoelectric layer 6A and the second piezoelectric layer 6B.

[0027] When the dimension along the electrode finger extension direction in the intersection region is defined as the intersection width, the intersection width in the first elastic wave resonator 1A and the intersection width in the second elastic wave resonator 1B are the same. However, the intersection widths may differ among the multiple elastic wave resonators of the elastic wave device 10.

[0028] The first elastic wave resonator 1A has a pair of reflectors. Specifically, the pair of reflectors of the first elastic wave resonator 1A are reflector 9A and reflector 9B. Reflectors 9A and 9B face each other with the first IDT electrode 7A in between. Similarly, the second elastic wave resonator 1B has a pair of reflectors. Specifically, the pair of reflectors of the second elastic wave resonator 1B are reflector 9C and reflector 9D. Reflectors 9C and 9D face each other with the second IDT electrode 7B in between. Each reflector is provided on the second piezoelectric layer 6B.

[0029] Reflector 9A has a pair of reflector busbars and a plurality of reflector electrode fingers. The pair of reflector busbars face each other. One end of each of the plurality of reflector electrode fingers is connected to one reflector busbar. The other end of each of the plurality of reflector electrode fingers is connected to the other reflector busbar. Reflectors 9B, 9C, and 9D are configured similarly to reflector 9A.

[0030] As shown in Figure 2, in this embodiment, the first dielectric film 8A and the second dielectric film 8B are each multilayer films. Specifically, the first dielectric film 8A includes a first layer 8a and a second layer 8b. The first layer 8a is provided on the second piezoelectric layer 6B. The second layer 8b is provided 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 provided on the second piezoelectric layer 6B. The second layer 8d is provided on the first layer 8c. The second IDT electrode 7B is embedded in the first layer 8c.

[0031] The first dielectric film 8A and the second dielectric film 8B are integrally formed from 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 from 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 integrally formed from the same material.

[0032] 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 those described above. Alternatively, the first dielectric film 8A and the second dielectric film 8B may each be single-layer dielectric films.

[0033] In a dielectric film formed by integrating the first dielectric film 8A and the second dielectric film 8B, the portion covering the first IDT electrode 7A is the first dielectric film 8A. In the dielectric film described above, the portion covering the second dielectric film 8B is the second dielectric film 8B. Note that the first dielectric film 8A and the second dielectric film 8B may be provided separately.

[0034] In this embodiment, the material combination of the support substrate 3 / first intermediate layer 4 / second intermediate layer 5 / first piezoelectric layer 6A / second piezoelectric layer 6B as a laminate is silicon / silicon nitride / silicon oxide / lithium niobate / lithium niobate. However, the materials of the support substrate 3, first intermediate layer 4, second intermediate layer 5, first piezoelectric layer 6A, and second piezoelectric layer 6B are not limited to the above.

[0035] The polarization direction of the first piezoelectric layer 6A and the polarization direction of the second piezoelectric layer 6B are different from each other. More specifically, in this embodiment, the polarization direction of the first piezoelectric layer 6A and the polarization direction of the second piezoelectric layer 6B are inversely related.

[0036] Here, at 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, it is said that the polarization directions are reversed in two piezoelectric layers that the difference between the second Euler angles θ in the two piezoelectric layers is within the range of 180° ± 5°. Hereafter, the Euler angle of the first piezoelectric layer 6A will be (φ1, θ1, ψ1), and the Euler angle of the second piezoelectric layer 6B will be (φ2, θ2, ψ2). The difference between angle θ1, which is the second Euler angle at the Euler angle (φ1, θ1, ψ1) of the first piezoelectric layer 6A, and angle θ2, which is the second Euler angle at the Euler angle (φ2, θ2, ψ2) of the second piezoelectric layer 6B, is within the range of 180° ± 5°. Note that the difference between the second Euler angle θ1 and the second Euler angle θ2 is not limited to the above.

[0037] The features of this embodiment are as follows: 1) The distance between the first piezoelectric layer 6A and the first IDT electrode 7A is different from the distance between the first piezoelectric layer 6A and the second IDT electrode 7B. 2) The polarization direction of the first piezoelectric layer 6A is different from the polarization direction of the second piezoelectric layer 6B. 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. This makes it possible to suppress unwanted waves in the first elastic wave resonator 1A and the second elastic wave resonator 1B, which function as multiple elastic wave resonators. The details of this will be explained below with reference to the elastic wave resonator of the comparative example.

[0038] As shown in Figure 3, the comparative example elastic wave resonator 101 differs from the first elastic wave resonator 1A in the first embodiment in that the IDT electrode 107 is not embedded in the dielectric film 108. The comparative example elastic wave resonator 101 also differs from the first elastic wave resonator 1A in the first embodiment in that the dielectric film 108 is a single-layer dielectric film.

[0039] Specifically, in the comparative example elastic wave resonator 101, the support member 2, the first piezoelectric layer 6A, and the second piezoelectric layer 6B are laminated, similar to the first embodiment. On the other hand, in the comparative example, unlike the first embodiment, the thickness of the dielectric film 108 is thinner than the thickness of the IDT electrode 107. The dielectric film 108 is provided on the second piezoelectric layer 6B so as to cover the IDT electrode 107. That is, the IDT electrode 107 is covered by the dielectric film 108, but is not embedded in the dielectric film 108.

[0040] In the comparative example elastic wave resonator 101, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the phase of the unwanted Rayleigh wave was derived by simulation for each different thickness of the second piezoelectric layer 6B. 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.

[0041] Figure 4 shows 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 comparative example elastic wave resonator.

[0042] As shown in Figure 4, in the comparative example, the relationship between the second Euler angle θ1 and the phase of the Rayleigh wave differs significantly for every 20 nm difference in the thickness of the second piezoelectric layer 6B. Therefore, for example, in an elastic wave apparatus, if multiple elastic wave resonators 101 of the comparative example, each with different thicknesses of the second piezoelectric layer 6B, are provided, it is difficult to suppress Rayleigh waves in all of the elastic wave resonators 101.

[0043] In contrast, in the first embodiment, Rayleigh waves, which are unwanted waves, can be suppressed in both the first elastic wave resonator 1A and the second elastic wave resonator 1B, in which the thickness of the second piezoelectric layer 6B is different from that of the first elastic wave resonator 1A and the second elastic wave resonator 1B shown in Figure 2.

[0044] Specifically, in the elastic wave resonator 1 shown in Figure 5, 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 stacked in this order. An IDT electrode 7 is provided on the second piezoelectric layer 6B. A dielectric film 8 is provided on the second piezoelectric layer 6B so as to cover the IDT electrode 7. The dielectric film 8 is a laminate of the first layer 8e and the second layer 8f. The IDT electrode 7 is embedded in the first layer 8e. The second layer 8f is provided on the first layer 8e.

[0045] 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 by simulation for each variation in the thickness of the second piezoelectric layer 6B. 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 pitch is denoted as λ. In this specification, unless otherwise specified, the thickness of the first layer in the dielectric film refers to the total thickness of the first layer. As will be discussed later, in some cases, the thickness of a portion of the first layer may be used as a parameter.

[0046] Support substrate: Material...Si, Thickness...100μm, Azimuth angle...(111), Euler angles (φ,θ,ψ)...(-45°,-54.7°,73°) First intermediate layer: Material...SiN, Thickness...50nm Second intermediate layer: Material...SiO2, Thickness...400nm First piezoelectric layer: Material…LiNbO3, Thickness…300nm, Euler angle (φ1,θ1,ψ1)…(0°,θ1,0°), Second Euler angle θ1…Varied in 0.5° increments within the range of 90° or more and 160° or less. Second piezoelectric layer: Material…LiNbO3, thickness…Varied in 10nm increments within the range of 10nm or more and 60nm or less. Euler angle (φ2,θ2,ψ2)…(0°,θ2,0°), second Euler angle θ2…θ1-180°, varied in 0.5° increments within the range of -90° or more and -20° or less. IDT electrodes: Material...NiCr / Pt / Ti / Al / Ti from the second piezoelectric layer side, Thickness...10nm / 30nm / 30nm / 150nm / 10nm from the second piezoelectric layer side, Duty cycle...0.5, Number of electrode fingers...100 pairs Wavelength λ: 1.5μm Cross width: 20λ First layer in dielectric film: Material...SiO2, Thickness...330nm Second layer in dielectric film: Material…SiN, thickness 30nm

[0047] Figure 6 shows 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 a configuration similar to that of the first and second elastic wave resonators in the first embodiment.

[0048] As shown in Figure 6, even if the thickness of the second piezoelectric layer 6B changes, the second Euler angle θ1 of the first piezoelectric layer 6A, where the phase of the Rayleigh wave is minimized, remains around 105° to 106°, showing almost no change. More precisely, as the thickness of the second piezoelectric layer 6B increases, the second Euler angle θ1 of the first piezoelectric layer 6A, where the phase of the Rayleigh wave is minimized, becomes slightly smaller. However, the change in the second Euler angle θ1 is less than 1°. Therefore, when an elastic wave device has multiple elastic wave resonators 1 with different thicknesses of the second piezoelectric layer 6B, the unwanted Rayleigh wave can be suppressed in any of the elastic wave resonators 1.

[0049] 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. Thus, in the elastic wave device 10, the first elastic wave resonator 1A and the second elastic wave resonator 1B, which are multiple elastic wave resonators, can suppress unwanted Rayleigh waves.

[0050] Incidentally, the resonant frequency of the first elastic wave resonator 1A can be adjusted by adjusting the thickness of the first dielectric film 8A. Similarly, the resonant frequency of the second elastic wave resonator 1B can be adjusted by adjusting the thickness of the second dielectric film 8B. The thicknesses of the first dielectric film 8A and the second dielectric film 8B may be different from each other. In this case, the resonant frequencies of the first elastic wave resonator 1A and the second elastic wave resonator 1B can be adjusted, respectively.

[0051] 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 bandwidths differ between the first elastic wave resonator 1A and the second elastic wave resonator 1B. The relative bandwidth is expressed as (|fa-fr| / fr)×100[%], where fr is the resonant frequency and fa is the anti-resonant frequency. For example, when the elastic wave device 10 is used as a filter device, the relative bandwidth can be adjusted by adjusting the thickness of the second piezoelectric layer 6B according to the resonant frequency or anti-resonant frequency of the first elastic wave resonator 1A. The same applies to the second elastic wave resonator 1B. The ability to adjust the relative bandwidth in the first elastic wave resonator 1A and the second elastic wave resonator 1B is demonstrated by referring to the elastic wave resonator 1 shown in Figure 5.

[0052] In the elastic wave resonator 1, the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A and the specific bandwidth was derived by simulation for each variation in the thickness of the second piezoelectric layer 6B. The design parameters of the elastic wave resonator 1 were the same as those used in the study shown in Figure 6.

[0053] Figure 7 shows the relationship between the thickness of the second piezoelectric layer, the second Euler angle of the first piezoelectric layer, and the specific bandwidth in an elastic wave resonator having a configuration similar to that of the first and second elastic wave resonators in the first embodiment.

[0054] As shown in Figure 7, the value of the relative bandwidth decreases as the thickness of the second piezoelectric layer 6B increases. Therefore, the relative bandwidth of the elastic wave resonator 1 can be adjusted by adjusting the thickness of the second piezoelectric layer 6B in the elastic wave resonator 1. On the other hand, even if the second Euler angle θ1 of the first piezoelectric layer 6A changes, the value of the relative bandwidth remains almost unchanged.

[0055] In the first elastic wave resonator 1A and the second elastic wave resonator 1B, which have a similar configuration to the elastic wave resonator 1, the relative bandwidth can be adjusted by adjusting the thickness of the second piezoelectric layer 6B, in each case.

[0056] 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 edge of the passband of the filter device, the relative bandwidth of the first elastic wave resonator 1A may be narrowed. In this case, the steepness can be increased. In this specification, high steepness means that, near the edge of the passband, the change in frequency is small for a given change in attenuation.

[0057] On the other hand, if the resonant frequency or anti-resonant frequency of the second elastic wave resonator 1B is far from the frequency at the edge of the passband of the filter device, the relative bandwidth of the second elastic wave resonator 1B may be widened. This makes it easier to reduce the insertion loss in the passband. In this way, the filter characteristics of the filter device using the elastic wave device 10 can be improved. Moreover, unwanted waves can be suppressed in 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.

[0058] As in the first embodiment, it is preferable that silicon oxide is used as the material for the first layer 8a and the first layer 8c in 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 in which silicon oxide is used as the material. This makes it possible to reduce the absolute value of the frequency temperature coefficient (TCF) in the first elastic wave resonator 1A and the second elastic wave resonator 1B. As a result, the frequency temperature characteristics of the first elastic wave resonator 1A and the second elastic wave resonator 1B can be improved.

[0059] It is preferable that silicon nitride is 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 makes it possible to increase the moisture resistance of the elastic wave device 10.

[0060] The inventors have found that the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, can be calculated from 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 a simulation was performed. As a result, Equation 1 below was derived, which is the relationship between the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, and the thickness of the second piezoelectric layer 6B and the thickness of the main electrode layer in the first IDT electrode 7A.

[0061] Support substrate: Material...Si, Thickness...100μm, Azimuth angle...(111), Euler angles (φ,θ,ψ)...(-45°,-54.7°,73°) First intermediate layer: Material...SiN, Thickness...50nm Second intermediate layer: Material...SiO2, Thickness...400nm First piezoelectric layer: Material…LiNbO3, Thickness…300nm, Euler angle (φ1,θ1,ψ1)…(0°,θ1,0°), Second Euler angle θ1…Varied within the range of 90° or more and 110° or less. The second piezoelectric layer consisted of LiNbO3 material, with a thickness of 10 nm, 30 nm, or 50 nm, an Euler angle (φ2, θ2, ψ2) of (0°, θ2, 0°), and a second Euler angle θ2 of θ1-180°, which was varied within the range of -90° to -70°. First IDT electrode: Material...NiCr / Pt / Ti / Al / Ti from the second piezoelectric layer side, Thickness...10nm / 10nm, 30nm or 50nm / 30nm / 150nm / 10nm from the second piezoelectric layer side, Duty cycle...0.5, Number of electrode fingers...100 pairs Wavelength λ1: 1μm Cross width: 20λ1 First layer in the first dielectric film: Material...SiO2, Thickness...330nm Second layer in the first dielectric film: Material…SiN, thickness 30nm

[0062] In Equation 1 below, the thickness of the main electrode layer in the first IDT electrode 7A is denoted as t_IDT [μm], and the thickness of the portion of the second piezoelectric layer 6B in which the first IDT electrode 7A is provided is denoted as t_piezo [μm]. The angle Theta [°] expressed in Equation 1 is the second Euler angle θ1 of the first piezoelectric layer 6A in which Rayleigh waves are suppressed.

[0063]

number

[0064] When the Euler angle (φ1, θ1, ψ1) in the first piezoelectric layer 6A is (0°, θ1, 0°), the second Euler angle θ1 is the angle Theta in Equation 1, thereby effectively suppressing Rayleigh waves in the first elastic wave resonator 1A.

[0065] In Equation 1, the angle Theta depends on the thickness of the second piezoelectric layer 6B. The thickness of the second piezoelectric layer 6B differs between the first elastic wave resonator 1A and the second elastic wave resonator 1B. However, the angle Theta does not change significantly even when the thickness of the second piezoelectric layer 6B changes. This is evident from Figures 6 and 7, which show that the second Euler angle θ1, at which Rayleigh waves are suppressed, does not change significantly even when the second piezoelectric layer 6B changes. Therefore, because the Euler angle (φ1,θ1,ψ1) of the first piezoelectric layer 6A is (0°,θ1,0°) and the second Euler angle θ1 is the angle Theta, Rayleigh waves can be effectively suppressed in the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0066] Further investigation revealed that if the first Euler angle φ1 is within the range of 0°±5°, the third Euler angle ψ1 is within the range of 0°±5°, and the second Euler angle θ1 is within the range of Theta±10°, the same effect as described above can be obtained. Therefore, it is preferable that the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A are (within the range of 0°±5°, θ1 is within the range of 0°±5°), and the second Euler angle θ1 is within the range of Theta±10°. This allows for effective suppression of Rayleigh waves in the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0067] In the first embodiment, lithium niobate is used as the material for the first piezoelectric layer 6A and the second piezoelectric layer 6B. However, even when lithium tantalate is used as the material for the first piezoelectric layer 6A and the second piezoelectric layer 6B, it is preferable that the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A are within the above range. That is, it is preferable that the Euler angles (φ1, θ1, ψ1) of the first piezoelectric layer 6A are within the range of 0°±5°, θ1 is within the range of 0°±5°, and the second Euler angle θ1 is within the range of Theta±10°. In this case as well, Rayleigh waves can be effectively suppressed in the first elastic wave resonator 1A and the second elastic wave resonator 1B.

[0068] In the following, as shown in Figure 2, t_d1 is defined as the thickness of the portion of the layer covering the first IDT electrode 7A in the first dielectric film 8A that is located on the first IDT electrode 7A. In the first embodiment, the layer covering the first IDT electrode 7A in the first dielectric film 8A is the first layer 8a. It is preferable that the thickness t_d1 of the first layer 8a is 0.25λ1 or less. This makes it possible to suppress higher-order modes in the first elastic wave resonator 1A. The details are shown below.

[0069] The design parameters for the first elastic wave resonator 1A were set as follows, and a simulation was performed. This allowed us to derive the range of thickness t_d1 of the first layer 8a in the first dielectric film 8A that can suppress higher-order modes.

[0070] Support substrate: Material...Si, Thickness...100μm, Azimuth angle...(111), Euler angles (φ,θ,ψ)...(-45°,-54.7°,73°) First intermediate layer: Material...SiN, Thickness...50nm Second intermediate layer: Material...SiO2, Thickness...400nm First piezoelectric layer: Material…LiNbO3, Thickness…300nm, Euler angles (φ1,θ1,ψ1)…(0°,105°,0°) Second piezoelectric layer: Material…LiNbO3, Thickness…10nm, Euler angles (φ2,θ2,ψ2)…(0°,-75°,0°) First IDT electrode: Material...NiCr / Pt / Ti / Al / Ti from the second piezoelectric layer side, Thickness...10nm / 30nm / 30nm / 150nm / 10nm from the second piezoelectric layer side, Duty cycle...0.5, Number of electrode fingers...100 pairs Wavelength λ1: 1.5μm Cross width: 20λ1 The first layer in the first dielectric film: Material...SiO2, Thickness t_d1...Varied in 100nm increments within the range of 100nm or more and 1000nm or less. Converted to wavelength λ1, it was varied in 0.067λ1 increments within the range of 0.067λ1 or more and 0.667λ1 or less. The overall thickness...Varied in 100nm increments within the range of 330nm or more and 1230nm or less. Second layer in the first dielectric film: Material…SiN, thickness 30nm

[0071] Figure 8 shows the relationship between the thickness of the portion of the first layer located on the first IDT electrode and the phase of the higher-order mode in the first dielectric film of the first embodiment.

[0072] As shown in Figure 8, when the thickness t_d1 of the first layer 8a in the first dielectric film 8A is greater than 0.25λ1, the suppression of higher-order modes in the first elastic wave resonator 1A is insufficient. In contrast, when the thickness t_d1 of the first layer 8a is 0.25λ1 or less, it can be seen that higher-order modes can be suppressed. Furthermore, it is even more preferable that the thickness t_d1 of the first layer 8a is 0.2λ1 or less. This allows for even greater suppression of higher-order modes in the first elastic wave resonator 1A.

[0073] Similarly, in the second elastic wave resonator 1B, it is preferable that the thickness t_d2 of the portion of the layer covering the second IDT electrode 7B in the second dielectric film 8B that is located on the second IDT electrode 7B is 0.25λ2 or less. Specifically, in the first embodiment, the layer covering the second IDT electrode 7B in the second dielectric film 8B is the first layer 8c. Therefore, it is preferable that the thickness t_d2 of the first layer 8c is 0.25λ2. This makes it possible to suppress higher-order modes in the second elastic wave resonator 1B. It is even more preferable that the thickness t_d2 of the first layer 8c is 0.2λ2 or less. This makes it possible to further suppress higher-order modes in the second elastic wave resonator 1B.

[0074] If the elastic wave device 10 has a plurality of first elastic wave resonators 1A, the thickness t_d1 of the first layer 8a in the first dielectric film 8A can be converted using the wavelength λ1 for each first elastic wave resonator 1A. In this case, it is preferable that the thickness t_d1 of the first layer 8a is 0.25λ1 or less, and more preferably 0.2λ1 or less, for at least one first elastic wave resonator 1A. This makes it possible to suppress higher-order modes in at least one first elastic wave resonator 1A. It is more preferable that the thickness t_d1 of the first layer 8a is 0.25λ1 or less, and even more preferable 0.2λ1 or less, for all first elastic wave resonators 1A. This makes it possible to suppress higher-order modes in all first elastic wave resonators 1A.

[0075] The same applies when the elastic wave device 10 has a plurality of second elastic wave resonators 1B. Specifically, for each second elastic wave resonator 1B, the thickness t_d2 of the first layer 8c in the second dielectric film 8B can be converted using the wavelength λ2. In this case, it is preferable that the thickness t_d2 of the first layer 8c in at least one second elastic wave resonator 1B is 0.25λ2 or less, and more preferably 0.2λ2 or less. This makes it possible to suppress higher-order modes in at least one second elastic wave resonator 1B. It is more preferable that the thickness t_d2 of the first layer 8c in all second elastic wave resonators 1B is 0.25λ2 or less, and even more preferably 0.2λ2 or less. This makes it possible to suppress higher-order modes in all second elastic wave resonators 1B.

[0076] Examples of materials for each layer of the support member 2, the first piezoelectric layer 6A and the second piezoelectric layer 6B, are shown below. In this specification, the main component refers to a component that accounts for more than 50 wt% of the member. The main component material may exist in one of the following states: single crystal, polycrystalline, or amorphous, or in a mixture thereof.

[0077] As the material for the support substrate 3, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; or semiconductors such as silicon; or materials mainly composed of the above materials can be used. The spinel mentioned above includes an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of the spinel mentioned above include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4. The same applies to the spinel mentioned later as an example of the material for the first intermediate layer 4. In the first embodiment, the support substrate 3 is a silicon support substrate.

[0078] In the first embodiment, the first intermediate layer 4 is a high-speed film. A high-speed film is a film in which the speed of sound of the propagating bulk wave is relatively high. More specifically, the speed of sound of the bulk wave propagating through the high-speed film is higher than the speed of sound of the elastic wave propagating through the first piezoelectric layer 6A and the second piezoelectric layer 6B. As the material for the first intermediate layer 4, which is a high-speed film, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; semiconductors such as silicon; or materials mainly composed of the above materials can be used. In the first embodiment, the first intermediate layer 4 is a silicon nitride layer.

[0079] On the other hand, the second intermediate layer 5 is a low-sound-velocity film. A low-sound-velocity film is a film in which the speed of sound of the propagating bulk wave is relatively low. More specifically, the speed of sound of the bulk wave propagating through the low-sound-velocity film is lower than the speed of sound of the bulk wave propagating through the first piezoelectric layer 6A and the second piezoelectric layer 6B. As the material for the second intermediate layer 5, which is a low-sound-velocity film, for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds of silicon oxide to which fluorine, carbon, or boron have been added, 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.

[0080] For example, lithium tantalate or lithium niobate can be used as the material 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. The polarization direction of the first piezoelectric layer 6A and the polarization direction of the second piezoelectric layer 6B are different from each other.

[0081] In the elastic wave apparatus 10, the first intermediate layer 4, which is a high-sound-velocity membrane, the second intermediate layer 5, which is a low-sound-velocity membrane, the first piezoelectric layer 6A, and the second piezoelectric layer 6B are stacked in this order. This allows the energy of the elastic waves to be effectively confined to the first piezoelectric layer 6A side and the second piezoelectric layer 6B side. Note that the support member 2 does not necessarily have to include the first intermediate layer 4 and the second intermediate layer 5.

[0082] In the first embodiment, all elastic wave resonators in the elastic wave apparatus 10 share the second piezoelectric layer 6B. However, some elastic wave resonators in the elastic wave apparatus 10 do not need to have the second piezoelectric layer 6B. This example is shown in the second embodiment.

[0083] Figure 9 is a schematic front cross-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.

[0084] This embodiment differs from the first embodiment in that the second elastic wave resonator 21B does not have a second piezoelectric layer 6B. Apart from the above, the elastic wave apparatus 20 of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment.

[0085] The second elastic wave resonator 21B shares the support member 2 and the first piezoelectric layer 6A with the first elastic wave resonator 1A. On the other hand, the second elastic wave resonator 21B does not share the second piezoelectric layer 6B with the first elastic wave resonator 1A. 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 provided directly on the first piezoelectric layer 6A. The second dielectric film 8B is provided directly on the first piezoelectric layer 6A so as to cover the second IDT electrode 7B. The second IDT electrode 7B is embedded in the second dielectric film 8B.

[0086] 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 provided on the first piezoelectric layer 6A via the second piezoelectric layer 6B. Therefore, the distance between the first IDT electrode 7A and the first piezoelectric layer 6A is the same as the thickness of the second piezoelectric layer 6B. Thus, the distance between the first piezoelectric layer 6A and the first IDT electrode 7A is different from the distance between the first piezoelectric layer 6A and the second IDT electrode 7B.

[0087] In this embodiment, the multiple elastic wave resonators in the elastic wave apparatus 20 include 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. Even in this case, unwanted Rayleigh waves can be suppressed in the multiple elastic wave resonators of the elastic wave apparatus 20. This is shown below.

[0088] 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 by simulation for each variation in the thickness of the second piezoelectric layer 6B. 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 derived by simulation. The design parameters for the first elastic wave resonator 1A are as follows.

[0089] Support substrate: Material...Si, Thickness...100μm, Azimuth angle...(111), Euler angles (φ,θ,ψ)...(-45°,-54.7°,73°) First intermediate layer: Material...SiN, Thickness...50nm Second intermediate layer: Material...SiO2, Thickness...400nm First piezoelectric layer: Material…LiNbO3, Thickness…300nm, Euler angle (φ1,θ1,ψ1)…(0°,θ1,0°), Second Euler angle θ1…Varied in 0.5° increments within the range of 90° or more and 160° or less. Second piezoelectric layer: Material…LiNbO3, thickness…Varied in 10nm increments within the range of 10nm or more and 60nm or less. Euler angle (φ2,θ2,ψ2)…(0°,θ2,0°), second Euler angle θ2…θ1-180°, varied in 0.5° increments within the range of -90° or more and -20° or less. First IDT electrode: Material...NiCr / Pt / Ti / Al / Ti from the second piezoelectric layer side, Thickness...10nm / 30nm / 30nm / 150nm / 10nm from the second piezoelectric layer side, Duty cycle...0.5, Number of electrode fingers...100 pairs Wavelength λ1: 1.3μm Cross width: 20λ1 First layer in the first dielectric film: Material...SiO2, Thickness...330nm Second layer in the first dielectric film: Material…SiN, thickness 30nm

[0090] The design parameters for the second elastic wave resonator 21B were the same as those for the first elastic wave resonator 1A, except that the thickness of the second piezoelectric layer 6B was 0, i.e., the second piezoelectric layer 6B was not provided.

[0091] Figure 10 shows 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 in the second embodiment. Figure 11 is an enlarged view of a portion of Figure 10.

[0092] As shown in Figures 10 and 11, the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, remains almost unchanged whether the thickness of the second piezoelectric layer 6B is not zero or zero. Therefore, between the first elastic wave resonator 1A having the second piezoelectric layer 6B and the second elastic wave resonator 21B not having the second piezoelectric layer 6B, the second Euler angle θ1 of the first piezoelectric layer 6A, which can suppress Rayleigh waves, remains almost unchanged. Consequently, 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, unwanted Rayleigh waves can be suppressed. [Explanation of Symbols]

[0093] 1… Elastic wave resonator 1A, 1B…First and second elastic wave resonators 2…Support member 3…Support substrate 4, 5…First and second intermediate layers 6A, 6B…First and second piezoelectric layers 7…IDT electrode 7A, 7B…First and second IDT electrodes 8…Dielectric film 8A, 8B…First and second dielectric films 8a, 8b... 1st and 2nd layers 8c, 8d... 1st and 2nd layers 8e, 8f... 1st and 2nd layers 9A~9D…Reflector 10... Elastic wave device 16, 17… 1st and 2nd bus bars 18, 19… First and second electrode fingers 20... Elastic wave device 21B...Second elastic wave resonator 101... Elastic wave resonator 107...IDT electrode 108…Dielectric film A...Cross area

Claims

1. A first elastic wave resonator comprising: a first piezoelectric layer; a second piezoelectric layer provided on the first piezoelectric layer; a first IDT electrode provided on the second piezoelectric layer and having a plurality of electrode fingers; and a first dielectric film provided on the second piezoelectric layer so as to cover the first IDT electrode; At least one elastic wave resonator sharing the first elastic wave resonator and the first piezoelectric layer, the at least one second elastic wave resonator comprising: a second IDT electrode directly or indirectly provided on the first piezoelectric layer and having a plurality of electrode fingers; and a second dielectric film directly or indirectly provided on the first piezoelectric layer so as to cover the second IDT electrode; Equipped with, 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 polarization direction of the first piezoelectric layer and the polarization direction of the second piezoelectric layer are different from each other. An elastic wave apparatus in which 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 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 provided on the second piezoelectric layer. The elastic wave apparatus according to claim 1, wherein in the second piezoelectric layer, the thickness of the portion where the first IDT electrode is provided and the thickness of the portion where the second IDT electrode is provided are different from each other.

3. The second IDT electrode is provided directly on the first piezoelectric layer, The elastic wave apparatus according to claim 1, wherein the second dielectric film is provided directly on the first piezoelectric layer so as to cover the second IDT electrode.

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

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

6. The first IDT electrode has at least one metal layer, and the first IDT electrode includes a main electrode layer whose proportion in all of the metal layers is more than 50 wt%, When the Euler angle of the first piezoelectric layer is (φ1, θ1, ψ1), the Euler angle of the first piezoelectric layer (φ1, θ1, ψ1) is (within the range of 0°±5°, θ1, within the range of 0°±5°), The elastic wave apparatus according to claim 5, wherein the thickness of the main electrode layer in the first IDT electrode is t_IDT [μm], the thickness of the portion of the second piezoelectric layer in which the first IDT electrode is provided is t_piezo [μm], and the angle represented by the following formula 1 is Theta [°], and the angle θ1 in the Euler angle (within the range of 0° ± 5°, θ1, within the range of 0° ± 5°) of the first piezoelectric layer is within the range of Theta ± 10°. [Math 1]

7. The wavelength defined by the electrode finger pitch in the first IDT electrode is λ １ In this case, the thickness of the portion of the layer covering the first IDT electrode in the first dielectric film that is located on the first IDT electrode is 0.25λ. １ The elastic wave apparatus according to any one of claims 1 to 6, which is as follows:

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

9. The acoustic wave apparatus according to any one of claims 1 to 8, wherein the first dielectric film and the second dielectric film are integrally provided from the same material.

Images