Elastic wave device

Abstract

An elastic wave device (1) comprises: a piezoelectric substrate (30) having main surfaces (30a, 30b) facing each other; an IDT electrode (11) disposed on the main surface (30a); and an IDT electrode (12) disposed on the main surface (30b). The piezoelectric substrate (30) includes a piezoelectric region (31) including the main surface (30a) and a piezoelectric region (32) including the main surface (30b). When the second Euler angle of the piezoelectric region (31) is θ1 and the second Euler angle of the piezoelectric region (32) is θ2, θ1 is [(0° to 75°) + 180° × n (n is an integer)] or [(155° to 180°) + 180° × n], and θ2 is (θ1 + 170°) to (θ1 + 190°).

Description

Elastic Wave Device

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

[0002] Patent Documents 1 and 2 disclose an elastic wave resonator that can be driven at a high-order mode resonance frequency and has a structure in which a first IDT (InterDigital Transducer) electrode, a first piezoelectric layer, a conductive layer, a second piezoelectric layer, and a second IDT electrode are stacked in this order.

[0003] JP 2007-312164 A JP 2008-516490 A

[0004] As the capacity of mobile communications increases, acoustic wave devices that meet the requirements of higher frequencies, wider bandwidths, and lower spurious emissions are in demand.

[0005] SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an acoustic wave device that satisfies the requirements of higher frequency, wider bandwidth, and lower spurious.

[0006] In order to achieve the above object, an elastic wave device according to one embodiment of the present invention includes a piezoelectric substrate having a first principal surface and a second principal surface opposing each other, a first IDT electrode arranged on the first principal surface, and a second IDT electrode arranged on the second principal surface, wherein the piezoelectric substrate includes a first piezoelectric region including the first principal surface and a second piezoelectric region including the second principal surface, and wherein, when a second Euler angle of the first piezoelectric region is θ1 and a second Euler angle of the second piezoelectric region is θ2, θ1 is [(0° or more and 75° or less) + 180° × n (n is an integer)] or [(155° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

[0007] According to the present invention, it is possible to provide an acoustic wave device that satisfies the requirements of higher frequency, wider bandwidth, and lower spurious.

[0008] FIG. 1 is a plan view and a cross-sectional view of an elastic wave device according to an embodiment. FIG. 2 is a cross-sectional view showing the polarization direction of a piezoelectric substrate according to an embodiment. FIG. 3A is a cross-sectional view of an elastic wave device according to Comparative Example 1. FIG. 3B is a cross-sectional view of an elastic wave device according to Comparative Example 2. FIG. 3C is a cross-sectional view of an elastic wave device according to Comparative Example 3. FIG. 3D is a cross-sectional view of an elastic wave device according to Example 1. FIG. 4 is a graph showing the resonance characteristics of the elastic wave device according to Example 1. FIG. 5 is a diagram illustrating elastic wave propagation modes of an elastic wave device. FIG. 6A is a graph showing the sound speed and electromechanical coupling coefficient in each mode of the elastic wave device according to Comparative Example 1. FIG. 6B is a graph showing the sound speed and electromechanical coupling coefficient in each mode of the elastic wave device according to Comparative Example 2. FIG. 6C is a graph showing the sound speed and electromechanical coupling coefficient in each mode of the elastic wave device according to Comparative Example 3. FIG. 6D is a graph showing the sound speed and electromechanical coupling coefficient in each mode of the elastic wave device according to Example 1. FIG. 7A is a graph showing a first range of the second Euler angles when the S2 mode is the principal mode in the elastic wave device according to Example 1. FIG. 7B is a graph showing a second range of the second Euler angles when the S2 mode is the principal mode in the elastic wave device according to Example 1. FIG. 7C is a graph showing a third range of the second Euler angles when the S2 mode is the principal mode in the elastic wave device according to Example 1. FIG. 8A is a cross-sectional view of an elastic wave device according to Example 2. FIG. 8B is a cross-sectional view of an elastic wave device according to Example 3. FIG. 8C is a cross-sectional view of an elastic wave device according to Example 4. FIG. 9 is a graph showing the relationship between the thickness of the piezoelectric substrate and the acoustic velocity in an elastic wave device according to an embodiment. FIG. 10 is a graph showing the relationship between the film thickness ratio of the piezoelectric region and the fractional bandwidth in an elastic wave device according to an embodiment. FIG. 11 is a graph showing the relationship between the IDT electrode film thickness and the fractional bandwidth in an elastic wave device according to an embodiment. FIG. 12A is a graph showing a first range of the IDT electrode finger duty in which the fractional resonance bandwidth of an elastic wave device according to an embodiment is 10% or more. FIG. 12B is a graph showing a second range of the IDT electrode finger duty in which the fractional resonance bandwidth of an elastic wave device according to an embodiment is 11% or more. 13A to 13C are diagrams illustrating a method for manufacturing a piezoelectric substrate of an elastic wave device according to an embodiment of the present invention. FIG. 14 is a cross-sectional view of an elastic wave device in accordance with Example 5.FIG. 15 is a plan view of an elastic wave device in accordance with a sixth embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0010] It should be noted that the drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present invention, and are not necessarily strictly illustrated, and may differ from the actual shapes, positional relationships, and proportions. In the drawings, the same reference numerals are used to denote substantially the same components, and redundant explanations may be omitted or simplified.

[0011] Furthermore, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not only represent strict meanings, but also include substantially equivalent ranges, for example, including an error of a few percent.

[0012] In addition, in the present disclosure, the passband of an acoustic wave device or an acoustic wave filter is defined as the frequency band between two frequencies that are 3 dB higher than the minimum insertion loss value within the passband.

[0013] Furthermore, in the resonance characteristics of the elastic wave device of the present disclosure, the resonance frequency and anti-resonance frequency are derived, for example, by contacting an RF probe with two input / output electrodes of the elastic wave device when the elastic wave device is not connected to other circuit elements, and measuring the reflection characteristics (impedance characteristics) using a network analyzer or the like.

[0014] In addition, in this disclosure, the term "major component of a material" refers to a component that accounts for more than 50% by weight of the material. The major component may be present in any one of single crystal, polycrystalline, and amorphous states, or in a mixture of these states.

[0015] In addition, in the present disclosure, two signals being in phase means that the phases are substantially the same, including a range in which the phases of the two signals differ by about 30%, for example.

[0016] Embodiments [1 Configuration of Elastic Wave Device 1 According to an Embodiment] FIG. 1 shows a plan view and a cross-sectional view of elastic wave device 1 according to an embodiment. FIG. 1A shows a plan view of main surface 30a of piezoelectric substrate 30 from the positive side of the z-axis. FIG. 1C shows a plan view (perspective) of main surface 30b of piezoelectric substrate 30 from the positive side of the z-axis. FIG. 1B shows a cross-sectional view taken along line Ib-Ib in FIGS. 1A and 1C. As shown in FIG. 1, elastic wave device 1 includes piezoelectric substrate 30, IDT electrodes 11 and 12, and reflecting electrodes 21 and 22. Note that the elastic wave device 1 shown in FIG. 1 is intended to illustrate a typical structure of an elastic wave resonator constituting elastic wave device 1. The number and lengths of electrode fingers constituting IDT electrodes 11 and 12 and reflecting electrodes 21 and 22 are not limited thereto.

[0017] The piezoelectric substrate 30 has a main surface 30a (first main surface) and a main surface 30b (second main surface), and includes piezoelectric regions 31 and 32. The piezoelectric substrate 30 is made of, for example, lithium niobate (LiNbO ３ ). That is, the piezoelectric substrate 30 can be made of, for example, lithium niobate or a material containing lithium niobate as a main component. The piezoelectric region 31 is an example of a first piezoelectric region and includes a main surface 30a and a main surface 30c (third main surface) opposite to the main surface 30a. The piezoelectric region 32 is an example of a second piezoelectric region and includes a main surface 30b and a main surface 30d (fourth main surface) opposite to the main surface 30b. Note that the piezoelectric regions 31 and 32 may be in contact with each other, in which case the main surfaces 30c and 30d coincide with each other.

[0018] The piezoelectric region 31 is a crystalline body whose second Euler angle θ1 is [(0° or more and 75° or less) + 180° × n (n is an integer)] or [(155° or more and 180° or less) + 180° × n]. The piezoelectric region 32 is a crystalline body whose second Euler angle θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

[0019] The piezoelectric substrate 30 is made of, for example, lithium tantalate (LiTaO ３ ), or a material containing lithium tantalate as a main component may also be used.

[0020] 2 is a cross-sectional view showing the polarization direction of piezoelectric substrate 30 according to an embodiment. This figure illustrates the cross-sectional view, crystal orientation, and polarization direction of elastic wave device 1 according to an embodiment, with the region between piezoelectric regions 31 and 32 omitted. As shown in the figure, the crystal orientation (first Euler angle, second Euler angle θ1, third Euler angle) of piezoelectric region 31 is, for example, (0°, 30°, 0°), and the second Euler angle θ1 is 30°. Furthermore, the crystal orientation (first Euler angle, second Euler angle θ2, third Euler angle) of piezoelectric region 32 is, for example, (0°, 210°, 0°), and the second Euler angle θ2 is 210°.

[0021] The above-described crystal structure of the piezoelectric regions 31 and 32 allows the piezoelectric regions 31 and 32 to have opposite polarization directions. In this embodiment, the main surface 30a is a positive surface, the main surfaces 30c and 30d are negative surfaces, and the main surface 30b is a positive surface.

[0022] The piezoelectric substrate 30 may be a single piezoelectric substrate 30, with the main surface 30a being a crystalline region having the second Euler angle θ1 and the main surface 30b being a crystalline region having the second Euler angle θ2. In this case, a crystalline region whose second Euler angle is neither θ1 nor θ2 may be disposed between the two crystalline regions. The piezoelectric substrate 30 may also have a structure in which two piezoelectric substrates are bonded together, with one piezoelectric substrate being a crystalline body having the second Euler angle θ1 and the other piezoelectric substrate being a crystalline body having the second Euler angle θ2.

[0023] The polarization of a piezoelectric region is determined by the degree of dipole orientation. The degree of dipole orientation is calculated by calculating the proportion of positive or negative polarization in the direction of polarization of the piezoelectric region. A dipole orientation of 50% in a piezoelectric region indicates that the piezoelectric region has equal amounts of positive and negative polarizations and does not have piezoelectricity. A dipole orientation of 100% indicates, for example, in the piezoelectric region 31, (1) all of the principal surfaces 30a are aligned in the positive direction and all of the principal surfaces 30c are aligned in the negative direction, or (2) all of the principal surfaces 30a are aligned in the negative direction and all of the principal surfaces 30c are aligned in the positive direction. A dipole orientation of less than 50% indicates, for example, that in the piezoelectric region 31, the principal surfaces 30a are biased toward one of the positive and negative directions and the principal surfaces 30c are biased toward the other of the positive and negative directions, resulting in the piezoelectric region 31 having piezoelectricity. In other words, when the degree of dipole orientation is not 50%, for example, in the piezoelectric region 31, the main surface 30a is one of the positive and negative surfaces, and the main surface 30c is the other of the positive and negative surfaces, and the piezoelectric region 31 has piezoelectricity. Note that the degree of dipole orientation is not less than 50%.

[0024] The degree of dipole orientation can be measured by determining the polarity through analysis using scanning nonlinear dielectric microscopy (SNDM) or a piezoelectric response microscope (PRM). For example, the polarity of the piezoelectric regions 31 and 32 can be determined by analyzing the main surfaces 30a and 30b using SNDM or PRM. The polarity of the piezoelectric regions 31 and 32 can also be determined by analyzing cross sections of the piezoelectric regions 31 and 32 using SNDM or PRM.

[0025] The second Euler angles of the piezoelectric regions 31 and 32 can be determined by an X-ray diffraction method such as XRD.

[0026] Returning to FIG. 1, the IDT electrodes 11 and 12 and the reflective electrodes 21 and 22 will be described.

[0027] The IDT electrode 11 is an example of a first IDT electrode, and is disposed on the main surface 30a of the piezoelectric substrate 30. As shown in FIG. 1A, the IDT electrode 11 has electrode fingers 111a and 111b and busbar electrodes 112a and 112b.

[0028] The plurality of electrode fingers 111a are an example of a plurality of first electrode fingers and are arranged parallel to one another. The plurality of electrode fingers 111b are an example of a plurality of second electrode fingers and are arranged parallel to one another. The plurality of electrode fingers 111a and the plurality of electrode fingers 111b are arranged parallel to one another so as to be interdigitated with one another.

[0029] The busbar electrode 112a is arranged to connect one ends of the electrode fingers 111a to each other. The busbar electrode 112a extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 111a (y-axis direction in FIG. 1 ). The busbar electrode 112b is arranged to connect one ends of the electrode fingers 111b to each other. The busbar electrode 112b extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 111b (y-axis direction in FIG. 1 ). The busbar electrode 112a and the busbar electrode 112b are arranged opposite each other, with the electrode fingers 111a and the electrode fingers 111b sandwiched between them. The other ends of the electrode fingers 111a face the busbar electrode 112b, and the other ends of the electrode fingers 111b face the busbar electrode 112a.

[0030] The reflecting electrodes 21 are arranged adjacent to the IDT electrode 11 on both sides of the IDT electrode 11 in a direction perpendicular to the extension direction of the electrode fingers 111a and 111b (the x-axis direction). The reflecting electrodes 21 can confine a predetermined acoustic wave excited by the IDT electrode 11 within the IDT electrode 11. Note that the acoustic wave device 1 does not necessarily have to include the reflecting electrodes 21.

[0031] The IDT electrode 12 is an example of a second IDT electrode, and is disposed on the main surface 30b of the piezoelectric substrate 30. As shown in FIG. 1C, the IDT electrode 12 has electrode fingers 121a and 121b and busbar electrodes 122a and 122b.

[0032] The plurality of electrode fingers 121a are an example of a plurality of third electrode fingers and are arranged parallel to one another. The plurality of electrode fingers 121b are an example of a plurality of fourth electrode fingers and are arranged parallel to one another. The plurality of electrode fingers 121a and the plurality of electrode fingers 121b are arranged parallel to one another so as to be interdigitated with one another.

[0033] The busbar electrode 122a is arranged to connect one ends of the electrode fingers 121a to each other. The busbar electrode 122a extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 121a (y-axis direction in FIG. 1 ). The busbar electrode 122b is arranged to connect one ends of the electrode fingers 121b to each other. The busbar electrode 122b extends in a direction (x-axis direction) intersecting the extension direction of the electrode fingers 121b (y-axis direction in FIG. 1 ). The busbar electrode 122a and the busbar electrode 122b are arranged opposite each other, with the electrode fingers 121a and the electrode fingers 121b sandwiched between them. The other ends of the electrode fingers 121a face the busbar electrode 122b, and the other ends of the electrode fingers 121b face the busbar electrode 122a.

[0034] The reflecting electrodes 22 are arranged on both sides of the IDT electrode 12 so as to be adjacent to the IDT electrode 12 in a direction perpendicular to the extension direction of the electrode fingers 121 a and 121 b (the x-axis direction). The reflecting electrodes 22 can confine a predetermined acoustic wave excited by the IDT electrode 12 within the IDT electrode 12. Note that the acoustic wave device 1 does not necessarily have to include the reflecting electrodes 22.

[0035] Here, a description will be given of the electrode parameters of the IDT electrodes 11 and 12. Note that although the electrode parameters of the IDT electrode 11 will be described below, the electrode parameters of the IDT electrode 12 are also defined in the same way.

[0036] The wavelength λ of the IDT electrode 11 is a unit of length defined by the repetition period of the electrode fingers 111a or 111b. The electrode finger duty D1 of the IDT electrode 11 is the line width occupancy rate of the electrode fingers 111a and 111b, and is the ratio of the line width L to the sum of the line width L and the space width S, and is defined as L / (L+S). In FIG. 1 , the thickness of the IDT electrode 11 is T11, the thickness of the IDT electrode 12 is T12, the thickness of the piezoelectric region 31 is T31, and the thickness of the piezoelectric region 32 is T32.

[0037] In the IDT electrode 11, when the interval between adjacent electrode fingers is not constant, the wavelength λ of the IDT electrode 11 is the average wavelength λ of the IDT electrode 11. ＡＶＥ The mean wavelength λ of the IDT electrode 11 is defined as follows: ＡＶＥ is defined as 2×Di / (Ni-1), where Ni is the total number of electrode fingers 111a and 111b included in the IDT electrode 11, and Di is the center-to-center distance between the electrode finger located at one end of the IDT electrode 11 and the electrode finger located at the other end in the elastic wave propagation direction.

[0038] When the IDT electrode 11 includes a so-called withdrawal electrode, the average wavelength λ ＡＶＥ In calculating the total number of electrode fingers Ni, the number of withdrawal electrodes is excluded from the total number of electrode fingers Ni, and the line width L of the withdrawal electrode and one of the two spaces (space width S) adjacent to the withdrawal electrode are excluded from the center-to-center distance Di.

[0039] The withdrawal electrodes include floating withdrawal electrodes, polarity-reversed electrodes, and solid electrodes. A floating withdrawal electrode is an electrode finger that is not connected to either of the two opposing busbar electrodes and is arranged parallel to the electrode fingers connected to one of the two busbar electrodes. A polarity-reversed electrode is an electrode finger that is connected to the same busbar electrode as the busbar electrodes to which the adjacent electrode fingers are connected and is arranged parallel to the adjacent electrode fingers. A solid electrode is an electrode finger that has an electrode finger width that is at least twice the average electrode finger width of the electrode fingers excluding the solid electrodes and is arranged parallel to the electrode fingers excluding the solid electrodes.

[0040] In addition, when the electrode finger duty D1 of the IDT electrode 11 is not constant, the electrode finger duty D1 of the IDT electrode 11 is equal to the average electrode finger duty D1 of the IDT electrode 11. ＡＶＥ The average electrode finger duty D1 of the IDT electrode 11 is defined as follows: ＡＶＥ The total number of electrode fingers 111a and 111b included in the IDT electrode 11 is Ni, and the total line width obtained by adding the line width L of (Ni-1) electrode fingers is L. ＡＬＬ The total space width obtained by adding up the (Ni-1) space widths S included in the IDT electrode 11 is S ＡＬＬ In this case, L ＡＬＬ / (L ＡＬＬ +S ＡＬＬ ) is defined as

[0041] In addition, when the IDT electrode 11 includes a so-called withdrawal electrode, the average electrode finger duty D1 ＡＶＥ When calculating the total line width L ＡＬＬ The line width L of the withdrawal electrode is excluded, and the total space width S ＡＬＬ One of the two spaces (space width S) adjacent to the withdrawal electrode is excluded.

[0042] The wavelength λ and electrode finger duty D1 of the IDT electrode 11 can be measured by using a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), or a transmission electron microscope (TEM) to view the main surface of the piezoelectric substrate 30 on which the IDT electrode 11 is formed in a plan view and / or to view a cross section perpendicular to the extension direction of the electrode fingers 111 a and 111 b, thereby measuring the line width L and the space width S.

[0043] In addition, in the elastic wave device 1 according to this embodiment, a dielectric film may be disposed at least between the main surface 30 a of the piezoelectric substrate 30 and the IDT electrode 11, between the main surface 30 b and the IDT electrode 12, and between the piezoelectric region 31 and the piezoelectric region 32.

[0044] 2. Configuration and Propagation Characteristics of Elastic Wave Device 1A in Accordance with First Example Next, the configuration and propagation characteristics of elastic wave device 1A in accordance with first example will be described in comparison with elastic wave devices in accordance with first to third comparative examples.

[0045] Fig. 3A is a cross-sectional view of an elastic wave device 500 in accordance with Comparative Example 1. Fig. 3B is a cross-sectional view of an elastic wave device 600 in accordance with Comparative Example 2. Fig. 3C is a cross-sectional view of an elastic wave device 700 in accordance with Comparative Example 3. Fig. 3D is a cross-sectional view of an elastic wave device 1A in accordance with Example 1.

[0046] 3D , elastic wave device 1A in accordance with Example 1 includes piezoelectric substrate 30 and IDT electrodes 11 and 12. Elastic wave device 1A in accordance with Example 1 differs from elastic wave device 1 in accordance with the embodiment in that the material, thickness, and polarization direction of the piezoelectric substrate, as well as the electrode finger arrangement of IDT electrodes 11 and 12, are specifically defined. Therefore, the following description of the configuration of elastic wave device 1A in accordance with Example 1 will omit a description of the same configuration as that of elastic wave device 1 in accordance with the embodiment, and will focus on the different configuration.

[0047] The piezoelectric substrate 30 includes piezoelectric regions 31 and 32. Each of the piezoelectric regions 31 and 32 is made of lithium niobate (LiNbO ３ The piezoelectric substrate 30 is a crystal of LiNbO ３ This configuration allows for high coupling of the secondary S-wave mode used as the main mode. The piezoelectric regions 31 and 32 have opposite polarization directions, with the main surface 30a of the piezoelectric region 31 and the main surface 30b of the piezoelectric region 32 being plus surfaces, and the main surfaces 30c and 30d being minus surfaces. In other words, with respect to the second Euler angle θ1 of the piezoelectric region 31, the second Euler angle θ2 of the piezoelectric region 32 is greater than or equal to [(θ1 + 170°) and less than or equal to (θ1 + 190°)].

[0048] The wavelength λ is 1.00 μm. The thickness of each of the piezoelectric regions 31 and 32 is 0.15×λ. The film thickness T11 of each of the electrode fingers 111a and 111b and the film thickness T12 of each of the electrode fingers 121a and 121b are 0.01×λ. The electrode finger duty D of the IDT electrodes 11 and 12 is 0.5. When the main surfaces 30a and 30b are viewed in plan, the electrode fingers 111a and 121a overlap, and the electrode fingers 111b and 121b overlap, so that the electrode fingers 111a and 121a are excited in phase, and the electrode fingers 111b and 121b are excited in phase.

[0049] 3A , elastic wave device 500 in accordance with Comparative Example 1 includes a piezoelectric substrate including piezoelectric region 31 and IDT electrode 11. Elastic wave device 500 in accordance with Comparative Example 1 is different from elastic wave device 1A in accordance with Example 1 in that it does not include IDT electrode 12, does not include piezoelectric region 32, and has a different thickness of piezoelectric region 31. Therefore, the following description of the configuration of elastic wave device 500 in accordance with Comparative Example 1 will omit a description of the same configuration as elastic wave device 1A in accordance with Example 1 and will focus on the different configuration.

[0050] The piezoelectric substrate includes a piezoelectric region 31. The piezoelectric region 31 is made of lithium niobate (LiNbO ３ ) crystal. The piezoelectric region 31 is polarized, with the principal surface of the piezoelectric region 31 on which the IDT electrode 11 is arranged being the positive surface, and the principal surface on which the IDT electrode 11 is not arranged being the negative surface. The thickness of the piezoelectric region 31 is 0.30×λ. The film thickness T11 of each of the electrode fingers 111a and 111b is 0.01×λ. The electrode finger duty D1 of the IDT electrode 11 is 0.5.

[0051] 3B , elastic wave device 600 in accordance with Comparative Example 2 includes a piezoelectric substrate including piezoelectric region 31 and IDT electrodes 11 and 12. Elastic wave device 600 in accordance with Comparative Example 2 differs from elastic wave device 1A in accordance with Example 1 in that it does not include piezoelectric region 32 and that piezoelectric region 31 has a different thickness. Therefore, the following description of the configuration of elastic wave device 600 in accordance with Comparative Example 2 will omit a description of the same configuration as elastic wave device 1A in accordance with Example 1 and will focus on the different configuration.

[0052] The piezoelectric substrate includes a piezoelectric region 31. The piezoelectric region 31 is made of lithium niobate (LiNbO ３ ) crystal. The piezoelectric region 31 is polarized, with the principal surface of the piezoelectric region 31 on which the IDT electrode 11 is arranged being the positive side, and the principal surface on which the IDT electrode 12 is arranged being the negative side. The thickness of the piezoelectric region 31 is 0.30×λ. The film thickness T11 of each of the electrode fingers 111a and 111b and the film thickness T12 of each of the electrode fingers 121a and 121b are 0.01×λ. The electrode finger duty D of the IDT electrodes 11 and 12 is 0.5.

[0053] 3C , elastic wave device 700 in accordance with Comparative Example 3 includes piezoelectric substrate 30 and IDT electrode 11. Elastic wave device 700 in accordance with Comparative Example 3 differs from elastic wave device 1A in accordance with Example 1 in that it does not include IDT electrode 12. Therefore, the following description of the configuration of elastic wave device 700 in accordance with Comparative Example 3 will focus on the different configuration and omit a description of the same configuration as elastic wave device 1A in accordance with Example 1. IDT electrode 12 is not provided on main surface 30b of piezoelectric substrate 30.

[0054] FIG. 4 is a graph showing the resonance characteristics of the elastic wave device 1A according to Example 1. As shown in the figure, in the elastic wave device 1A according to Example 1, resonance in a second-order S-wave mode (hereinafter referred to as S2 mode) occurs between 14 and 17 GHz. The S2 mode has an antiresonance frequency fa at which impedance is maximized and a resonance frequency fr at which impedance is minimized. The sound velocity in the S2 mode resonance is high, at 15,000 m / s or greater. Furthermore, the resonance fractional bandwidth (the value obtained by dividing the difference frequency between the antiresonance frequency and the resonance frequency by the resonance frequency) is 11.6%, which is a wide bandwidth. Furthermore, spurious signals (SP1, SP2, and SP3 in FIG. 4 ) occurring in a band outside the S2 mode resonance are suppressed compared to the S2 mode resonance. That is, by inverting the polarization of the piezoelectric regions 31 and 32 and arranging the IDT electrodes 11 and 12, which are driven in phase, on both the main surfaces 30a and 30b of the piezoelectric substrate 30, it is possible to efficiently excite the S2 mode, which has a high acoustic velocity, and by setting the wavelength λ to about 1 μm, it becomes possible to drive at a frequency of 10 GHz or more. Furthermore, by configuring the IDT electrodes 11 and 12 and the piezoelectric substrate 30 to be symmetrical in the thickness direction of the piezoelectric substrate 30, it is possible to suppress out-of-band spurious emissions.

[0055] The elastic wave modes are explained in FIG. 5 . FIG. 5 is a diagram illustrating the elastic wave propagation modes of an elastic wave device. As shown in the figure, the elastic wave propagation modes are classified into S, A, and SH modes based on vibration in the x-axis direction, z-axis direction, and y-axis direction relative to the propagation direction of the elastic wave (positive x-axis direction). These modes are further classified into zeroth, first, and second order modes. Among these modes, by using the S2 mode (second-order S wave), whose main component is a longitudinal wave (vibration in the x-axis direction), as the elastic wave, it is possible to obtain propagation characteristics of high sound speed, wide bandwidth, and spurious suppression.

[0056] FIG. 6A shows the acoustic velocity and electromechanical coupling coefficient k in each mode of the elastic wave device 500 in accordance with Comparative Example 1. ２ 10 is a graph showing the acoustic velocity (left graph) and the electromechanical coupling coefficient k when the second Euler angle θ1 of the piezoelectric region 31 is changed from 0° to 180°. ２As shown in the right diagram of FIG. 6A, the electromechanical coupling coefficient k in the SH0 mode (zeroth-order SH wave) is larger than that in other modes. ２ However, as shown in the left figure, the sound velocity in the SH0 mode is 5000 m / s or less, which is a low sound velocity.

[0057] FIG. 6B shows the acoustic velocity and electromechanical coupling coefficient k in each mode of the elastic wave device 600 in accordance with Comparative Example 2. ２ 10 is a graph showing the acoustic velocity (left graph) and the electromechanical coupling coefficient k when the second Euler angle θ1 of the piezoelectric region 31 is changed from 0° to 180°. ２ As shown in the right diagram of FIG. 6B, the electromechanical coupling coefficient k in the SH0 mode (zeroth-order SH wave) is larger than that in other modes. ２ However, as shown in the left figure, the sound velocity in the SH0 mode is 5000 m / s or less, which is a low sound velocity.

[0058] FIG. 6C shows the acoustic velocity and electromechanical coupling coefficient k in each mode of the elastic wave device 700 in accordance with Comparative Example 3. ２ 10 is a graph showing the acoustic velocity (left graph) and the electromechanical coupling coefficient k when the second Euler angle θ1 of the piezoelectric region 31 is changed from 0° to 180°. ２ As shown in the left diagram of FIG. 6C, the sound velocity is 15,000 m / s or more in the S2 mode and the A2 mode, but as shown in the right diagram, the electromechanical coupling coefficient k ２ It is not possible to secure a large amount of bandwidth and achieve wide bandwidth.

[0059] FIG. 6D shows the acoustic velocity and electromechanical coupling coefficient k in each mode of the elastic wave device 1A in accordance with Example 1. ２ 10 is a graph showing the acoustic velocity (left graph) and the electromechanical coupling coefficient k when the second Euler angle θ1 of the piezoelectric region 31 is changed from 0° to 180°. ２ As shown in the left diagram of FIG. 6D, the sound velocity in the S2 mode is 15,000 m / s or more, and as shown in the right diagram, the electromechanical coupling coefficient k ２ Therefore, the range of the second Euler angle θ1 can be determined so that the above-mentioned condition can be largely ensured.

[0060] 7A is a graph showing a first range of the second Euler angle θ1 when the S2 mode is the principal mode in the elastic wave device 1A in accordance with Example 1. The graph shows the relationship between the electromechanical coupling coefficient k and the second Euler angle θ1 of the piezoelectric region 31 when the second Euler angle θ1 is changed from 0° to 180°. ２ From the figure, in the S2 mode where the sound velocity is 15,000 m / s or more, the electromechanical coupling coefficient k ２ It can be seen that the range of the second Euler angle θ1 that can ensure a value of 10 or more is [(0° or more and 75° or less) + 180° × n (n is an integer)] or [(155° or more and 180° or less) + 180° × n]. In addition, by setting the range of θ1 as described above, the electromechanical coupling coefficient k ２ It is possible to reduce the value to approximately 10 or less.

[0061] 7B is a graph showing a second range of the second Euler angle θ1 when the S2 mode is the principal mode in the elastic wave device 1A in accordance with Example 1. The graph shows the relationship between the electromechanical coupling coefficient k ２ From the figure, the electromechanical coupling coefficient k of the S2 mode where the sound velocity is 15,000 m / s or more is ２ can be secured to 10 or more, and the electromechanical coupling coefficient k ２ The range of the second Euler angle θ1 that makes θ1 equal to or less than 4 is [(0° or more and 50° or less) + 180° × n (n is an integer)] or [(165° or more and 180° or less) + 180° × n].

[0062] This makes it possible to reduce spurious emissions due to the SH1 mode in the attenuation band of elastic wave device 1A to a level that does not affect the attenuation characteristics of elastic wave device 1A.

[0063] 7C is a graph showing a third range of the second Euler angle θ1 when the S2 mode is the principal mode in the elastic wave device 1A in accordance with Example 1. The graph shows the relationship between the electromechanical coupling coefficient k ２ From the figure, the electromechanical coupling coefficient k of the S2 mode where the sound velocity is 15,000 m / s or more is２ can be secured to 10 or more, and the electromechanical coupling coefficient k ２ The range of the second Euler angle θ1 for which is 2 or less is [(12.5° or more and 45° or less) + 180° × n (n is an integer)].

[0064] This makes it possible to reduce spurious emissions due to the SH1 mode in the attenuation band of elastic wave device 1A to a level that does not affect the attenuation characteristics of elastic wave device 1A.

[0065] 8A is a cross-sectional view of elastic wave device 1B according to Example 2. As shown in the figure, elastic wave device 1B includes piezoelectric substrate 30, IDT electrodes 11 and 12, a frame 41, and a support substrate 40. Elastic wave device 1B according to Example 2 differs from elastic wave device 1A according to Example 1 in that it includes frame 41 and support substrate 40. Therefore, the following description of the configuration of elastic wave device 1B according to Example 2 will omit a description of the same components as elastic wave device 1A according to Example 1 and will focus on the different components.

[0066] When the main surface 30b is viewed from above, the frame 41 is disposed in the outer edge region of the main surface 30b so as to surround the IDT electrode 12, and is configured to secure a hollow space above the main surface 30b so that the IDT electrode 12 does not come into contact with any member other than the main surface 30b. The frame 41 may be made of a conductor such as metal, silicon, or a resin member.

[0067] The support substrate 40 is bonded to the frame 41 and configured to support the piezoelectric substrate 30 and the IDT electrodes 11 and 12. The support substrate 40 can be made of, for example, a piezoelectric material such as silicon, aluminum nitride, lithium tantalate, lithium niobate, or quartz; a ceramic material such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite; a dielectric material such as diamond or glass; a semiconductor material such as gallium nitride; a resin; or a material primarily composed of any of the above materials. Including silicon in the support substrate 40 increases the thermal conductivity of the support substrate 40, thereby improving the heat dissipation and power durability of the acoustic wave device 1B. Furthermore, the processing precision of the support substrate 40 is improved.

[0068] According to the above configuration, it is possible to prevent the acoustic waves propagating through the piezoelectric substrate 30 from leaking to the support substrate 40, and therefore it is possible to excite the acoustic waves in the main mode with low loss.

[0069] 8B is a cross-sectional view of elastic wave device 1C according to Example 3. As shown in the figure, elastic wave device 1C includes piezoelectric substrate 30, IDT electrodes 11 and 12, and a frame 42. Elastic wave device 1C according to Example 3 differs from elastic wave device 1B according to Example 2 in that it does not include support substrate 40. Therefore, the following description of the configuration of elastic wave device 1C according to Example 3 will focus on the differences and omit a description of the same components as elastic wave device 1B according to Example 2.

[0070] When the main surface 30b is viewed from above, the frame 42 is disposed in the outer edge region of the main surface 30b so as to surround the IDT electrode 12, and is configured to secure a hollow space above the main surface 30b so that the IDT electrode 12 does not come into contact with any member other than the main surface 30b. The frame 42 may be made of a conductor such as metal, silicon, or a resin member.

[0071] According to the above configuration, it is possible to excite the main mode of the acoustic waves propagating through the piezoelectric substrate 30 with low loss.

[0072] 8C is a cross-sectional view of an elastic wave device 1D according to Example 4. As shown in the figure, the elastic wave device 1D includes a piezoelectric substrate 30, IDT electrodes 11 and 12, a dielectric layer 50, a low acoustic impedance layer 61, a high acoustic impedance layer 62, and a support substrate 40. The elastic wave device 1D according to Example 4 differs from the elastic wave device 1A according to Example 1 in that it includes a dielectric layer 50, a low acoustic impedance layer 61, a high acoustic impedance layer 62, and a support substrate 40. Therefore, the following description of the configuration of the elastic wave device 1D according to Example 4 will focus on the differences and omit a description of the same components as those of the elastic wave device 1A according to Example 1.

[0073] The dielectric layer 50 is disposed so as to cover the main surface 30b and the IDT electrode 12. The dielectric layer 50 is made of, for example, silicon dioxide (SiO ２ ) is the main component.

[0074] The low acoustic impedance layer 61 is bonded to the high acoustic impedance layer 62 and has an acoustic impedance lower than that of the high acoustic impedance layer 62. The high acoustic impedance layer 62 is bonded to the low acoustic impedance layer 61. The low acoustic impedance layer 61 and the high acoustic impedance layer 62 constitute an energy trapping layer, and are arranged between the dielectric layer 50 and the support substrate 40 in the following order: low acoustic impedance layer 61, high acoustic impedance layer 62, low acoustic impedance layer 61, and high acoustic impedance layer 62. The energy trapping layer needs to have at least one low acoustic impedance layer 61 and one high acoustic impedance layer 62, and may have three or more low acoustic impedance layers 61 and three or more high acoustic impedance layers 62.

[0075] The low acoustic impedance layer 61 may be a layer in which the sound velocity of the bulk waves propagating through the low acoustic impedance layer 61 is slower than that of the bulk waves propagating through the piezoelectric substrate 30, and may be, for example, a dielectric such as silicon oxide, glass, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or a material containing any of the above materials as a main component.

[0076] The high acoustic impedance layer 62 may be a layer in which the bulk wave acoustic velocity propagating through the high acoustic impedance layer 62 is faster than the acoustic velocity of the elastic wave propagating through the piezoelectric substrate 30, and examples of materials that can be used include piezoelectric materials such as silicon nitride, aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectrics such as diamond and glass; semiconductors such as silicon and gallium nitride; metals such as tungsten; or resins, or materials containing any of the above materials as their main components.

[0077] According to the above configuration, the dielectric layer 50, the energy trapping layer, and the support substrate 40 that support the piezoelectric substrate 30 are not membrane-shaped, which increases the mechanical strength of the elastic wave device 1D. Furthermore, because the piezoelectric substrate 30 is in contact with the support substrate 40 via the dielectric layer 50 and the energy trapping layer rather than via air, the heat dissipation path has high thermal conductivity, allowing heat generated in the IDT electrodes 11 and 12 to be efficiently dissipated to the support substrate 40.

[0078] 6. Thickness of Piezoelectric Region and IDT Electrode of Acoustic Wave Device 1 Next, suitable ranges for the thickness of piezoelectric substrate 30 and the film thicknesses of IDT electrodes 11 and 12 of acoustic wave device 1 according to this embodiment will be described.

[0079] FIG. 9 is a graph showing the relationship between the thickness of the piezoelectric substrate 30 and the sound velocity in the elastic wave device 1 according to this embodiment.

[0080] In the elastic wave device 1 from which the characteristics shown in FIG. 9 were obtained, piezoelectric regions 31 and 32 were each made of lithium niobate crystal. Piezoelectric regions 31 and 32 had opposite polarization directions, and principal surfaces 30a and 30b were positive surfaces. Wavelength λ was 1.00 μm. Film thicknesses T11 and T12 of IDT electrodes 11 and 12 were each 0.01×λ. Electrode finger duty D of IDT electrodes 11 and 12 was 0.5. When principal surfaces 30a and 30b were viewed from above, electrode fingers 111a and 121a overlapped, and electrode fingers 111b and 121b overlapped. Electrode fingers 111a and 121a were excited in phase, and electrode fingers 111b and 121b were excited in phase.

[0081] 9 , the sound velocity in the S2 mode, which is the main mode, increases as the total thickness (T31 + T32) of the piezoelectric region 31 and the piezoelectric region 32 decreases. When the total thickness (T31 + T32) is 0.6 × λ or less, the sound velocity in the S2 mode is 10,000 m / s or greater, and by setting the wavelength λ to approximately 1.0 μm, elastic wave device 1 can be driven at 10 GHz or greater.

[0082] FIG. 10 is a graph showing the relationship between the film thickness ratio of piezoelectric regions 31 and 32 and the relative resonance bandwidth of elastic wave device 1 according to this embodiment.

[0083] In the elastic wave device 1 for which the characteristics shown in FIG. 10 were obtained, piezoelectric regions 31 and 32 were each made of lithium niobate crystal. Piezoelectric regions 31 and 32 had opposite polarization directions, and principal surfaces 30a and 30b were positive surfaces. Wavelength λ was 1.00 μm. Film thicknesses T11 and T12 of IDT electrodes 11 and 12 were each 0.01×λ. Electrode finger duty D of IDT electrodes 11 and 12 was 0.5. When principal surfaces 30a and 30b were viewed from above, electrode fingers 111a and 121a overlapped, and electrode fingers 111b and 121b overlapped. Electrode fingers 111a and 121a were excited in phase, and electrode fingers 111b and 121b were excited in phase.

[0084] 10 , as the ratio of thickness T31 of piezoelectric region 31 to thickness T32 of piezoelectric region 32 (piezoelectric region film thickness ratio) approaches 1.0, the relative resonance bandwidth of the dominant S2 mode becomes larger. When the piezoelectric region film thickness ratio is 0.5 or more and 2.0 or less, the relative resonance bandwidth of the S2 mode becomes 6% or more, and elastic wave device 1 having a wide passband can be provided.

[0085] FIG. 11 is a graph showing the relationship between the IDT electrode film thickness and the relative resonance bandwidth of elastic wave device 1 according to this embodiment.

[0086] In the elastic wave device 1 from which the characteristics shown in FIG. 11 were obtained, piezoelectric regions 31 and 32 were each made of lithium niobate crystal. Piezoelectric regions 31 and 32 had opposite polarization directions, and principal surfaces 30a and 30b were positive surfaces. The wavelength λ was 1.00 μm. The thickness T31 of piezoelectric region 31 and the thickness T32 of piezoelectric region 32 were each 0.15×λ. The electrode finger duty D of IDT electrodes 11 and 12 was 0.5. When principal surfaces 30a and 30b were viewed from above, electrode fingers 111a and 121a overlapped, and electrode fingers 111b and 121b overlapped. Electrode fingers 111a and 121a were excited in phase, and electrode fingers 111b and 121b were excited in phase.

[0087] 11 , the smaller the thickness T11 of IDT electrode 11 and the thickness T12 of IDT electrode 12 (IDT electrode film thickness), the larger the relative resonance bandwidth of the S2 mode, which is the dominant mode. When the IDT electrode film thickness is 0.06 mm or less, the relative resonance bandwidth of the S2 mode is 7% or more, making it possible to provide an acoustic wave device 1 with a wide passband.

[0088] In the characteristic results shown in FIG. 11, the thickness T11 of the IDT electrode 11 and the thickness T12 of the IDT electrode 12 are the same, but the thickness T11 and the thickness T12 may be different.

[0089] 7. Electrode Finger Duty of Acoustic Wave Device 1 Next, a suitable range of the electrode finger duty of IDT electrodes 11 and 12 in acoustic wave device 1 according to this embodiment will be described.

[0090] 12A is a graph showing a first range of electrode finger duties in which the resonance ratio band of elastic wave device 1 according to this embodiment is 10% or more, and FIG. 12B is a graph showing a second range of electrode finger duties in which the resonance ratio band of elastic wave device 1 according to this embodiment is 11% or more.

[0091] In the elastic wave device 1 from which the characteristics shown in FIGS. 12A and 12B were obtained, piezoelectric regions 31 and 32 were each made of lithium niobate crystals. Piezoelectric regions 31 and 32 had opposite polarization directions, and principal surfaces 30a and 30b were positive surfaces. The wavelength λ was 1.00 μm. The thickness T31 of piezoelectric region 31 and the thickness T32 of piezoelectric region 32 were each 0.15×λ. The thickness T11 of IDT electrode 11 and the thickness T12 of IDT electrode 12 were each 0.01×λ. When principal surfaces 30a and 30b were viewed from above, electrode fingers 111a and 121a overlapped, and electrode fingers 111b and 121b overlapped. Electrode fingers 111a and 121a were excited in phase, and electrode fingers 111b and 121b were excited in phase.

[0092] As shown in FIG. 12A , when the electrode finger duty D1 of the IDT electrode 11 and the electrode finger duty D2 of the IDT electrode 12 are included in region A (within the thick solid line), the resonance ratio band of the S2 mode is 10% or more, and an elastic wave device 1 having a wide passband can be provided. Specifically, region A is defined as follows: (1) 0.15≦D1≦0.20 and 0.35≦D2≦0.60, (2) 0.20≦D1≦0.25 and 0.25≦D2≦0.65, (3) 0.25≦D1≦0.35 and 0.20≦D2≦0.70, (4) 0.35≦D1≦0.40 and 0.15≦D2≦0.70, (5) 0.40≦D1≦0.60 and 0.15≦D2≦0.75, (6) 0.60≦D1≦0.65 and 0.20≦D2≦0.75, (7) 0.65≦D1≦0.70 and 0.25≦D2≦0.70, and (8) 0.70≦D1≦0.75 and 0.35≦D2≦0.65.

[0093] 12B , when electrode finger duty D1 of IDT electrode 11 and electrode finger duty D2 of IDT electrode 12 are included in region B (enclosed by a thick solid line), the resonance ratio band of the S2 mode is 11% or more, thereby providing an acoustic wave device 1 having a wide passband. Region B specifically includes: (1) 0.30≦D1≦0.35 and 0.40≦D2≦0.55, (2) 0.35≦D1≦0.40 and 0.35≦D2≦0.60, (3) 0.40≦D1≦0.55 and 0.30≦D2≦0.65, (4) 0.55≦D1≦0.60 and 0.35≦D2≦0.60, and (5) 0.60≦D1≦0.65 and 0.40≦D2≦0.55.

[0094] 8. Polarization Direction of Elastic Wave Device Next, the polarization direction of the piezoelectric substrate of an elastic wave device according to the present invention will be described. In elastic wave device 1 according to the embodiment (and elastic wave device 1A according to Example 1), as shown in FIG. 2 , main surface 30a of piezoelectric region 31 is the positive side, main surface 30c of piezoelectric region 31 is the negative side, main surface 30b of piezoelectric region 32 is the positive side, and main surface 30d of piezoelectric region 32 is the negative side. In other words, main surfaces 30a and 30b in contact with IDT electrodes 11 and 12 are the positive sides.

[0095] 13 is a diagram illustrating a method for manufacturing piezoelectric substrate 30 of elastic wave device 1 according to an embodiment. When polarization inversion is generated by performing polarization processing on a single piezoelectric substrate, a substrate with polarization inversion can be easily manufactured by designating the main surface on which the IDT electrodes are formed as the positive surface.

[0096] First, as shown in FIG. 13A, a piezoelectric substrate 30p is prepared. At this time, the main surface of the piezoelectric substrate 30p facing the support substrate is a positive surface. Next, as shown in FIG. 13B, a polarization inversion process is performed on the main surface facing the element surface. Finally, as shown in FIG. 13C, a piezoelectric substrate 30 is fabricated in which the main surface facing the element surface and the main surface facing the support substrate are both positive surfaces.

[0097] It is possible to fabricate an elastic wave device 1E in which the polarization direction is opposite to that of elastic wave device 1 according to the embodiment and elastic wave device 1A according to Example 1. FIG. 14 is a cross-sectional view of elastic wave device 1E according to Example 5. Elastic wave device 1E shown in FIG. 14 includes piezoelectric substrate 30D and IDT electrodes 11 and 12. Elastic wave device 1E according to Example 5 has a different polarization direction of piezoelectric substrate 30D than elastic wave device 1A according to Example 1. Therefore, the following description of the configuration of elastic wave device 1E according to Example 5 will omit a description of the same components as elastic wave device 1A according to Example 1 and will focus on the different components.

[0098] 14 , in elastic wave device 1E in accordance with Example 5, principal surface 30a on which IDT electrode 11 of piezoelectric region 31D is arranged and principal surface 30b on which IDT electrode 12 of piezoelectric region 32D is arranged are negative surfaces, and the bonding surface between piezoelectric region 31D and piezoelectric region 32D is a positive surface. In other words, the principal surface in contact with IDT electrodes 11 and 12 is a negative surface.

[0099] According to the above configuration, the main surface on which IDT electrodes 11 and 12 are formed is the negative side, which can prevent unintended polarization inversion from occurring due to charges generated during the manufacturing process of elastic wave device 1E.

[0100] 15 is a plan view of an elastic wave device 1F according to a sixth embodiment. As shown in the figure, the elastic wave device 1F includes a piezoelectric substrate 30, IDT electrodes 11F and 12 (not shown), a reflecting electrode 21, and mass adding films 71 and 72. The IDT electrode 11F is disposed on the principal surface 30a, and the IDT electrode 12 is disposed on the principal surface 30b. The elastic wave device 1F according to the sixth embodiment differs from the elastic wave device 1A according to the first embodiment in that it includes mass adding films 71 and 72. Therefore, the following description of the configuration of the elastic wave device 1F according to the sixth embodiment will focus on the differences and omit a description of the same components as those of the elastic wave device 1A according to the first embodiment.

[0101] The busbar electrode 112a connects one ends of the plurality of electrode fingers 111a together, and the busbar electrode 112b connects one ends of the plurality of electrode fingers 111b together.

[0102] The mass adding film 71 is disposed across the other ends of the electrode fingers 111 b so as to extend in a direction intersecting the extension direction of the electrode fingers 111 a and the electrode fingers 111 b. The mass adding film 72 is disposed across the other ends of the electrode fingers 111 a so as to extend in a direction intersecting the extension direction. The mass adding films 71 and 72 are made of, for example, a dielectric material.

[0103] According to this, the IDT electrode 11F has a so-called 3D piston structure, and the acoustic waves propagating through the other ends of the plurality of electrode fingers 111 a and the other ends of the plurality of electrode fingers 111 b have a lower acoustic velocity than the acoustic waves propagating through the region between the other ends of the plurality of electrode fingers 111 a and the other ends of the plurality of electrode fingers 111 b, thereby suppressing spurious responses in the transverse mode.

[0104] In the acoustic wave device 1F, the above-described mass-adding film may be formed on at least one of the IDT electrodes 11F and 12F.

[0105] In addition, in the elastic wave device 1F, the tips of the electrode fingers may be irregularly shaped instead of the mass addition films 71 and 72. Specifically, the electrode fingers 111a may have irregularly shaped portions at one end of the electrode fingers 111a that are wider than the electrode fingers 111a at the other end of the electrode fingers 111a. The electrode fingers 111b may have irregularly shaped portions at the other end of the electrode fingers 111b that are wider than the electrode fingers 111b at the one end of the electrode fingers 111b.

[0106] Alternatively, the electrode fingers 111a may have an irregular portion at one end thereof that is thicker than the electrode fingers 111a at the other end thereof, and the electrode fingers 111b may have an irregular portion at the other end thereof that is thicker than the electrode fingers 111b at the one end thereof.

[0107] According to this, the IDT electrode 11F has a so-called 2D piston structure, and the acoustic waves propagating through the other ends of the plurality of electrode fingers 111 a and the other ends of the plurality of electrode fingers 111 b have a lower acoustic velocity than the acoustic waves propagating through the region between the other ends of the plurality of electrode fingers 111 a and the other ends of the plurality of electrode fingers 111 b, thereby suppressing spurious responses in the transverse mode.

[0108] It is sufficient that at least one of IDT electrodes 11F and 12F of elastic wave device 1F has the irregular-shaped portion.

[0109] [10 Effects, etc.] As described above, elastic wave device 1 according to the embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6) includes piezoelectric substrate 30 having principal surfaces 30a and 30b facing each other, IDT electrode 11 arranged on principal surface 30a, and IDT electrode 12 arranged on principal surface 30b. Piezoelectric substrate 30 includes piezoelectric region 31 including principal surface 30a and piezoelectric region 32 including principal surface 30b. When the second Euler angle of piezoelectric region 31 is θ1 and the second Euler angle of piezoelectric region 32 is θ2, θ1 is [(0° or more and 75° or less) + 180° × n (n is an integer)] or [(155° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or less (θ1 + 190°).

[0110] According to this, in the S2 mode where the sound velocity is 15,000 m / s or more, the electromechanical coupling coefficient k ２ can be secured to 10 or more, and the electromechanical coupling coefficient k ２ It is possible to reduce the ratio of the S2 mode resonance frequency to approximately 10 or less. In other words, the S2 mode resonance, which has a high acoustic velocity and a large resonance band ratio, can be used as the main mode resonance. Furthermore, spurious signals occurring in bands other than the S2 mode resonance band can be efficiently suppressed. This makes it possible to provide an elastic wave device 1 that satisfies the requirements of high frequency, wide bandwidth, and low spurious signals.

[0111] Furthermore, for example, in elastic wave device 1 according to the present embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6), piezoelectric substrate 30 is made of lithium niobate.

[0112] This allows the electromechanical coupling coefficient in the main mode to be increased, and acoustic wave devices 1A to 1F with wide bandwidth and low loss can be provided.

[0113] For example, in the elastic wave device 1 according to the embodiment (and the elastic wave devices 1A to 1F according to Examples 1 to 6), θ1 is [(0° or more and 50° or less) + 180° × n] or [(165° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

[0114] According to this, in the S2 mode where the sound velocity is 15,000 m / s or more, the electromechanical coupling coefficient k ２ can be secured to 10 or more, and the electromechanical coupling coefficient k of the mode other than the S2 mode ２ It is therefore possible to provide an acoustic wave device 1 that satisfies the requirements of higher frequency, wider bandwidth, and lower spurious emissions.

[0115] For example, in the elastic wave device 1 according to the embodiment (and the elastic wave devices 1A to 1F according to Examples 1 to 6), θ1 is [(12.5° or more and 45° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

[0116] According to this, in the S2 mode where the sound velocity is 15,000 m / s or more, the electromechanical coupling coefficient k ２ can be secured to 10 or more, and the electromechanical coupling coefficient k of the mode other than the S2 mode ２ It is therefore possible to provide an acoustic wave device 1 that satisfies the requirements of higher frequency, wider bandwidth, and lower spurious emissions.

[0117] Furthermore, for example, in elastic wave device 1 according to the embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6), IDT electrode 11 includes a plurality of electrode fingers 111a and a plurality of electrode fingers 111b arranged parallel to each other, busbar electrode 112a configured to connect one ends of electrode fingers 111a to each other, and busbar electrode 112b configured to connect one ends of electrode fingers 111b to each other and arranged opposite busbar electrode 112a across electrode fingers 111a and 111b. IDT electrode 12 includes a plurality of electrode fingers 121a and a plurality of electrode fingers 121b arranged parallel to each other, busbar electrode 122a configured to connect one ends of electrode fingers 121a to each other, and busbar electrode 122b configured to connect one ends of electrode fingers 121b to each other and arranged opposite busbar electrode 122a across electrode fingers 121a and 121b.

[0118] Furthermore, for example, in the elastic wave device 1 according to the embodiment (and the elastic wave devices 1A to 1F according to Examples 1 to 6), when the main surfaces 30a and 30b are viewed in a plane, the plurality of electrode fingers 111a overlaps the plurality of electrode fingers 121a, the plurality of electrode fingers 111b overlaps the plurality of electrode fingers 121b, the plurality of electrode fingers 111a and the plurality of electrode fingers 121a are excited in phase, and the plurality of electrode fingers 111b and the plurality of electrode fingers 121b are excited in phase.

[0119] This makes it possible to efficiently excite the S2 mode having a high acoustic velocity, and also to efficiently suppress out-of-band spurious emissions.

[0120] Furthermore, for example, in the elastic wave device 1 according to the embodiment (and the elastic wave devices 1A to 1F according to Examples 1 to 6), when the repeating period of the multiple electrode fingers 111a is the wavelength λ, the thickness T11 of the IDT electrode 11 and the thickness T12 of the IDT electrode 12 are each 0.06 × λ or less.

[0121] This allows the S2 mode resonance band ratio to be 7% or more, making it possible to provide an elastic wave device 1 having a wide passband.

[0122] Furthermore, for example, in the elastic wave device 1 according to the embodiment (and the elastic wave devices 1A to 1F according to Examples 1 to 6), when the repeating period of the multiple electrode fingers 111a is the wavelength λ, the sum of the thickness of the piezoelectric region 31 in the direction perpendicular to the main surface 30a and the thickness of the piezoelectric region 32 in the direction perpendicular to the main surface 30b is 0.6 × λ or less.

[0123] This allows the acoustic velocity in the S2 mode to be 10,000 m / s or higher, making it possible to drive the acoustic wave device 1 at 10 GHz or higher.

[0124] For example, in the elastic wave device 1 according to the embodiment (and the elastic wave devices 1A to 1F according to Examples 1 to 6), the ratio of the thickness of the piezoelectric region 31 in a direction perpendicular to the main surface 30a to the thickness of the piezoelectric region 32 in a direction perpendicular to the main surface 30b is 0.5 or more and 2.0 or less.

[0125] This allows the resonance frequency band of the S2 mode to be 6% or more, making it possible to provide an elastic wave device 1 having a wide passband.

[0126] Furthermore, for example, in elastic wave device 1 according to an embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6), electrode finger duty D1 of IDT electrode 11 and electrode finger duty D2 of IDT electrode 12 are within the range of region A shown in FIG. 12A.

[0127] This allows the fractional resonance band of the S2 mode to be 10% or more, making it possible to provide an elastic wave device 1 having a wide passband.

[0128] Furthermore, for example, in elastic wave device 1 according to an embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6), electrode finger duty D1 of IDT electrode 11 and electrode finger duty D2 of IDT electrode 12 are within the range of region B shown in FIG. 12B.

[0129] This allows the fractional resonance bandwidth of the S2 mode to be 11% or more, making it possible to provide an elastic wave device 1 having a wide passband.

[0130] For example, in the elastic wave device 1 according to the embodiment (and the elastic wave device 1A according to Example 1), the piezoelectric region 31 includes a main surface 30a and a main surface 30c opposite to the main surface 30a, the piezoelectric region 32 includes a main surface 30b and a main surface 30d opposite to the main surface 30b, the main surface 30a of the piezoelectric region 31 is the positive surface, the main surface 30c of the piezoelectric region 31 is the negative surface, the main surface 30b of the piezoelectric region 32 is the positive surface, and the main surface 30d of the piezoelectric region 32 is the negative surface.

[0131] According to this, since the main surfaces 30a and 30b on which the IDT electrodes are formed are positive surfaces, when polarization reversal is generated by performing a polarization process on a single piezoelectric substrate, a polarization-reversed piezoelectric substrate can be easily produced.

[0132] For example, in the elastic wave device 1E according to Example 5, the piezoelectric region 31 includes a main surface 30a and a main surface 30c opposite to the main surface 30a, the piezoelectric region 32 includes a main surface 30b and a main surface 30d opposite to the main surface 30b, the main surface 30a of the piezoelectric region 31 is the negative surface, the main surface 30c of the piezoelectric region 31 is the positive surface, the main surface 30b of the piezoelectric region 32 is the negative surface, and the main surface 30d of the piezoelectric region 32 is the positive surface.

[0133] In this way, the main surface on which IDT electrodes 11 and 12 are formed is the negative side, which can prevent unintended polarization inversion from occurring due to charges generated during the manufacturing process of elastic wave device 1E.

[0134] For example, in the elastic wave device 1F of Example 6, the elastic waves propagating through the other ends of the multiple electrode fingers 111a and the elastic waves propagating through the other ends of the multiple electrode fingers 111b have a slower acoustic velocity than the elastic waves propagating through the region between the other ends of the multiple electrode fingers 111a and the other ends of the multiple electrode fingers 111b.

[0135] This makes it possible to suppress spurious transverse modes.

[0136] For example, the elastic wave device 1B according to Example 2 (and the elastic wave device 1C according to Example 3) further includes a frame body 41 (42) arranged in the outer edge region of the main surface 30b so as to surround the IDT electrode 12 when the main surface 30b is viewed in a plane.

[0137] This allows a hollow space to be secured above the main surface 30b so that the IDT electrode 12 does not come into contact with any member other than the main surface 30b, making it possible to excite the main mode of the elastic wave propagating through the piezoelectric substrate 30 with low loss.

[0138] For example, the elastic wave device 1B in accordance with the second embodiment further includes a support substrate 40 that is bonded to the frame 41 and supports the piezoelectric substrate 30 and the IDT electrodes 11 and 12, and the support substrate 40 contains silicon.

[0139] This prevents acoustic waves propagating through piezoelectric substrate 30 from leaking to support substrate 40, enabling acoustic waves in the main mode to be excited with low loss. Furthermore, since support substrate 40 contains silicon, the thermal conductivity of support substrate 40 is increased, improving the heat dissipation and power durability of acoustic wave device 1B. Furthermore, the processing precision of support substrate 40 is improved.

[0140] For example, the elastic wave device 1D according to the fourth embodiment further includes a support substrate 40, a dielectric layer 50 arranged to cover the main surface 30b and the IDT electrode 12, and an energy trapping layer arranged between the support substrate 40 and the dielectric layer 50, and the energy trapping layer includes a low acoustic impedance layer 61 and a high acoustic impedance layer 62 joined to the low acoustic impedance layer 61 and having an acoustic impedance higher than that of the low acoustic impedance layer 61.

[0141] This configuration increases the mechanical strength of acoustic wave device 1D because dielectric layer 50, energy trapping layer, and support substrate 40 that support piezoelectric substrate 30 are not membrane-shaped. Furthermore, because piezoelectric substrate 30 is in contact with support substrate 40 via dielectric layer 50 and the energy trapping layer rather than via air, the heat dissipation path has high thermal conductivity, allowing heat generated in IDT electrodes 11 and 12 to be efficiently dissipated to support substrate 40.

[0142] Furthermore, for example, elastic wave device 1 according to the present embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6) utilizes longitudinal waves as the main mode.

[0143] This makes it possible to simultaneously achieve higher frequencies, wider bandwidths, and lower spurious emissions.

[0144] Furthermore, for example, elastic wave device 1 according to the present embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6) utilizes secondary S waves as the main mode.

[0145] This makes it possible to simultaneously achieve higher frequencies, wider bandwidths, and lower spurious emissions.

[0146] Furthermore, for example, elastic wave device 1 according to the embodiment (and elastic wave devices 1A to 1F according to Examples 1 to 6) is driven at a frequency of 10 GHz or higher.

[0147] This makes it possible to meet the demands for higher frequencies.

[0148] While the elastic wave device according to the present invention has been described above with reference to embodiments and examples, the present invention is not limited to the above embodiments and examples. The present invention also includes other embodiments realized by combining any of the components in the above embodiments and examples, as well as modifications that are conceivable by those skilled in the art without departing from the spirit and scope of the present invention.

[0149] The features of the acoustic wave devices described based on the above embodiments and examples will be described below.

[0150] <1> An elastic wave device comprising: a piezoelectric substrate having first and second principal surfaces opposing each other; a first IDT electrode arranged on the first principal surface; and a second IDT electrode arranged on the second principal surface, wherein the piezoelectric substrate includes a first piezoelectric region including the first principal surface and a second piezoelectric region including the second principal surface, wherein, when a second Euler angle of the first piezoelectric region is θ1 and a second Euler angle of the second piezoelectric region is θ2, θ1 is [(0° or more and 75° or less) + 180° × n (n is an integer)] or [(155° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or less (θ1 + 190°).

[0151] <2> The acoustic wave device according to <1>, wherein the piezoelectric substrate is made of lithium niobate.

[0152] <3> The elastic wave device according to <1> or <2>, wherein θ1 is [(0° or more and 50° or less) + 180° × n] or [(165° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

[0153] <4> The elastic wave device according to any one of <1> to <3>, wherein θ1 is [(12.5° or more and 45° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

[0154] <5> The elastic wave device according to any one of <1> to <4>, wherein the first IDT electrode includes: a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel to each other; a first bus bar electrode configured to connect one ends of the first electrode fingers to each other; and a second bus bar electrode configured to connect one ends of the second electrode fingers to each other and disposed opposite the first bus bar electrode with the first electrode fingers and the second electrode fingers interposed therebetween; and the second IDT electrode includes: a plurality of third electrode fingers and a plurality of fourth electrode fingers arranged in parallel to each other; a third bus bar electrode configured to connect one ends of the third electrode fingers to each other; and a fourth bus bar electrode configured to connect one ends of the fourth electrode fingers to each other and disposed opposite the third bus bar electrode with the third electrode fingers and the fourth electrode fingers interposed therebetween.

[0155] <6> The elastic wave device according to <5>, wherein, when the first principal surface and the second principal surface are viewed in a plan view, the plurality of first electrode fingers overlap the plurality of third electrode fingers, the plurality of second electrode fingers overlap the plurality of fourth electrode fingers, the plurality of first electrode fingers and the plurality of third electrode fingers are excited in phase, and the plurality of second electrode fingers and the plurality of fourth electrode fingers are excited in phase.

[0156] <7> The acoustic wave device according to <5> or <6>, wherein, when a repetition period of the plurality of first electrode fingers is a wavelength λ, the film thickness of the first IDT electrode and the film thickness of the second IDT electrode are each 0.06×λ or less.

[0157] <8> The elastic wave device according to any one of <5> to <7>, wherein, when a repetition period of the plurality of first electrode fingers is a wavelength λ, the sum of a thickness of the first piezoelectric region in a direction perpendicular to the first main surface and a thickness of the second piezoelectric region in a direction perpendicular to the second main surface is 0.6×λ or less.

[0158] <9> The elastic wave device according to any one of <1> to <8>, wherein a ratio of a thickness of the first piezoelectric region in a direction perpendicular to the first main surface to a thickness of the second piezoelectric region in a direction perpendicular to the second main surface is 0.5 or more and 2.0 or less.

[0159] <10> The acoustic wave device according to any one of <1> to <9>, wherein the electrode finger duty of the first IDT electrode and the electrode finger duty of the second IDT electrode are within a range of region A shown in FIG. 12A .

[0160] <11> The acoustic wave device according to any one of <1> to <10>, wherein the electrode finger duty of the first IDT electrode and the electrode finger duty of the second IDT electrode are within a range of region B illustrated in FIG. 12B .

[0161] <12> The elastic wave device according to any one of <1> to <11>, wherein the first piezoelectric region includes the first main surface and a third main surface opposite to the first main surface, the second piezoelectric region includes the second main surface and a fourth main surface opposite to the second main surface, the first main surface of the first piezoelectric region is a positive surface, the third main surface of the first piezoelectric region is a negative surface, the second main surface of the second piezoelectric region is a positive surface, and the fourth main surface of the second piezoelectric region is a negative surface.

[0162] <13> The elastic wave device according to any one of <1> to <11>, wherein the first piezoelectric region includes the first main surface and a third main surface opposite to the first main surface, the second piezoelectric region includes the second main surface and a fourth main surface opposite to the second main surface, the first main surface of the first piezoelectric region is a negative surface, the third main surface of the first piezoelectric region is a positive surface, the second main surface of the second piezoelectric region is a negative surface, and the fourth main surface of the second piezoelectric region is a positive surface.

[0163] <14> The elastic wave device according to any one of <5> to <8>, wherein the acoustic wave propagating through the other ends of the first electrode fingers and the acoustic wave propagating through the other ends of the second electrode fingers have a slower acoustic velocity than the acoustic wave propagating through the region between the other ends of the first electrode fingers and the other ends of the second electrode fingers.

[0164] <15> The elastic wave device according to any one of <1> to <14>, further including a frame body that is arranged in an outer edge region of the second main surface so as to surround the second IDT electrode when the second main surface is viewed in a plane.

[0165] <16> The acoustic wave device according to <15>, further comprising: a support substrate bonded to the frame body and supporting the piezoelectric substrate, the first IDT electrode, and the second IDT electrode, wherein the support substrate contains silicon.

[0166] <17> The elastic wave device according to any one of <1> to <14>, further comprising: a support substrate; a dielectric layer arranged to cover the second principal surface and the second IDT electrode; and an energy trapping layer arranged between the support substrate and the dielectric layer, wherein the energy trapping layer includes: a low acoustic impedance layer; and a high acoustic impedance layer joined to the low acoustic impedance layer and having an acoustic impedance higher than that of the low acoustic impedance layer.

[0167] <18> The acoustic wave device according to any one of <1> to <17>, wherein the acoustic wave device uses a longitudinal wave as a main mode.

[0168] <19> The elastic wave device according to any one of <1> to <18>, wherein the elastic wave device uses a second-order S wave as a main mode.

[0169] <20> The acoustic wave device according to any one of <1> to <19>, wherein the acoustic wave device is driven at a frequency of 10 GHz or higher.

[0170] INDUSTRIAL APPLICABILITY The present invention can be widely used as an acoustic wave device disposed in a front end portion of communication devices such as mobile phones.

[0171] 1, 1A, 1B, 1C, 1D, 1E, 1F, 500, 600, 700 Acoustic wave device 11, 11F, 12 IDT electrode 21, 22 Reflecting electrode 30, 30D, 30p Piezoelectric substrate 30a, 30b, 30c, 30d Main surface 31, 31D, 32, 32D Piezoelectric region 40 Support substrate 41, 42 Frame 50 Dielectric layer 61 Low acoustic impedance layer 62 High acoustic impedance layer 71, 72 Mass-adding film 111a, 111b, 121a, 121b Electrode fingers 112a, 112b, 122a, 122b Bus bar electrode T11, T12 Film thickness T31, T32 Thickness

Claims

1. An elastic wave device comprising: a piezoelectric substrate having first and second principal surfaces opposing each other; a first IDT (InterDigital Transducer) electrode disposed on the first principal surface; and a second IDT electrode disposed on the second principal surface, wherein the piezoelectric substrate includes a first piezoelectric region including the first principal surface and a second piezoelectric region including the second principal surface, wherein, when a second Euler angle of the first piezoelectric region is θ1 and a second Euler angle of the second piezoelectric region is θ2, θ1 is [(0° or more and 75° or less) + 180° × n (n is an integer)] or [(155° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

2. The acoustic wave device according to claim 1, wherein the piezoelectric substrate is made of lithium niobate.

3. The elastic wave device according to claim 1 or 2, wherein θ1 is [(0° or more and 50° or less) + 180° × n] or [(165° or more and 180° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

4. The elastic wave device according to any one of claims 1 to 3, wherein θ1 is [(12.5° or more and 45° or less) + 180° × n], and θ2 is (θ1 + 170°) or more and (θ1 + 190°) or less.

5. The elastic wave device according to any one of claims 1 to 4, wherein the first IDT electrode includes: a plurality of first electrode fingers and a plurality of second electrode fingers arranged in parallel to each other; a first bus bar electrode configured to connect one ends of the plurality of first electrode fingers together; and a second bus bar electrode configured to connect one ends of the plurality of second electrode fingers together and arranged opposite the first bus bar electrode with the plurality of first electrode fingers and the plurality of second electrode fingers between them; and the second IDT electrode includes: a plurality of third electrode fingers and a plurality of fourth electrode fingers arranged in parallel to each other; a third bus bar electrode configured to connect one ends of the plurality of third electrode fingers together; and a fourth bus bar electrode configured to connect one ends of the plurality of fourth electrode fingers together and arranged opposite the third bus bar electrode with the plurality of third electrode fingers and the plurality of fourth electrode fingers between them.

6. The elastic wave device according to claim 5, wherein, when the first principal surface and the second principal surface are viewed in a plan view, the plurality of first electrode fingers and the plurality of third electrode fingers overlap, the plurality of second electrode fingers and the plurality of fourth electrode fingers overlap, the plurality of first electrode fingers and the plurality of third electrode fingers are excited in phase, and the plurality of second electrode fingers and the plurality of fourth electrode fingers are excited in phase.

7. The acoustic wave device according to claim 5 or 6, wherein, when the repetition period of the plurality of first electrode fingers is wavelength λ, the film thickness of the first IDT electrode and the film thickness of the second IDT electrode are each 0.06×λ or less.

8. The elastic wave device according to any one of claims 5 to 7, wherein, when the repeating period of the plurality of first electrode fingers is defined as wavelength λ, the sum of the thickness of the first piezoelectric region in a direction perpendicular to the first main surface and the thickness of the second piezoelectric region in a direction perpendicular to the second main surface is 0.6 × λ or less.

9. The elastic wave device according to any one of claims 1 to 8, wherein the ratio of the thickness of the first piezoelectric region in the direction perpendicular to the first main surface to the thickness of the second piezoelectric region in the direction perpendicular to the second main surface is 0.5 or more and 2.0 or less.

10. The acoustic wave device according to any one of claims 1 to 9, wherein the electrode finger duty of the first IDT electrode and the electrode finger duty of the second IDT electrode are within the range of region A shown in Figure 12A.

11. The acoustic wave device according to any one of claims 1 to 10, wherein the electrode finger duty of the first IDT electrode and the electrode finger duty of the second IDT electrode are within the range of region B shown in Figure 12B.

12. The elastic wave device according to any one of claims 1 to 11, wherein the first piezoelectric region includes the first main surface and a third main surface opposite the first main surface, the second piezoelectric region includes the second main surface and a fourth main surface opposite the second main surface, the first main surface of the first piezoelectric region is a positive surface, the third main surface of the first piezoelectric region is a negative surface, the second main surface of the second piezoelectric region is a positive surface, and the fourth main surface of the second piezoelectric region is a negative surface.

13. The elastic wave device according to any one of claims 1 to 11, wherein the first piezoelectric region includes the first main surface and a third main surface opposite the first main surface, the second piezoelectric region includes the second main surface and a fourth main surface opposite the second main surface, the first main surface of the first piezoelectric region is a negative surface, the third main surface of the first piezoelectric region is a positive surface, the second main surface of the second piezoelectric region is a negative surface, and the fourth main surface of the second piezoelectric region is a positive surface.

14. The elastic wave device according to any one of claims 5 to 8, wherein the elastic waves propagating through the other ends of the plurality of first electrode fingers and the elastic waves propagating through the other ends of the plurality of second electrode fingers have a slower acoustic velocity than the elastic waves propagating through the region between the other ends of the plurality of first electrode fingers and the other ends of the plurality of second electrode fingers.

15. The elastic wave device according to any one of claims 1 to 14, further comprising a frame body arranged in an outer edge region of the second principal surface so as to surround the second IDT electrode when the second principal surface is viewed in plan.

16. The acoustic wave device according to claim 15, further comprising a support substrate bonded to the frame body and supporting the piezoelectric substrate, the first IDT electrode, and the second IDT electrode, wherein the support substrate contains silicon.

17. The elastic wave device according to any one of claims 1 to 14, further comprising: a support substrate; a dielectric layer arranged to cover the second principal surface and the second IDT electrode; and an energy trapping layer arranged between the support substrate and the dielectric layer, wherein the energy trapping layer includes a low acoustic impedance layer and a high acoustic impedance layer joined to the low acoustic impedance layer and having an acoustic impedance higher than that of the low acoustic impedance layer.

18. The elastic wave device according to any one of claims 1 to 17, wherein the elastic wave device utilizes longitudinal waves as a primary mode.

19. The elastic wave device according to any one of claims 1 to 18, wherein the elastic wave device utilizes a second-order S wave as a main mode.

20. The acoustic wave device according to any one of claims 1 to 19, wherein the acoustic wave device is driven at a frequency of 10 GHz or higher.

Images