Elastic wave device

Abstract

To reduce the spurs of Rayleigh mode generated in a frequency band on a lower frequency side than an excitation mode used to obtain a characteristic, and the spurs of a high-order mode generated in a frequency band on a higher frequency side than the excitation mode. An elastic wave device (1) includes a support substrate (2), a laminate (3), and an IDT electrode (6). The laminate (3) includes a lithium tantalate piezoelectric layer and a lithium niobate piezoelectric layer that are laminated, and is provided on the support substrate (2). The IDT electrode (6) is provided on the laminate (3) and includes a plurality of electrode fingers (63). When a wavelength of an elastic wave determined by a pitch (P1) of the plurality of electrode fingers (63) is λ, a thickness of the laminate (3) is 0.66λ or less.

Description

Technical Field

[0001] This invention generally relates to elastic wave devices, and more specifically, to elastic wave devices having IDT (Interdigital Transducer) electrodes. Background Technology

[0002] Patent Document 1 describes a conventional elastic wave device. The elastic wave device described in Patent Document 1 includes a high-velocity acoustic support substrate (support substrate), a piezoelectric film (piezoelectric layer), and an IDT electrode. In the elastic wave device described in Patent Document 1, the IDT electrode is formed on one surface of the piezoelectric film.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2012 / 086639 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, in the conventional elastic wave device described in Patent Document 1, the following problem exists: Rayleigh mode spurious signals may occur in frequency bands lower than the excitation mode used to obtain the desired characteristics, and higher-order mode spurious signals may occur in frequency bands higher than the excitation mode. As a result, the characteristics of the device deteriorate.

[0008] The present invention was made in view of the above aspects. The object of the present invention is to provide an elastic wave device capable of reducing Rayleigh mode spurious emissions generated in a frequency band lower than the excitation mode used to obtain the characteristics, and higher-order mode spurious emissions generated in a frequency band higher than the excitation mode.

[0009] means for solving problems

[0010] An elastic wave device according to one aspect of the present invention includes a support substrate, a laminate, and an IDT electrode. The laminate comprises a stacked lithium tantalate piezoelectric layer and a lithium niobate piezoelectric layer, and is disposed on the support substrate. The IDT electrode is disposed on the laminate and has a plurality of electrode fingers. When the wavelength of the elastic wave, determined by the spacing of the plurality of electrode fingers, is defined as λ, the thickness of the laminate is 0.66λ or less.

[0011] Invention Effects

[0012] According to the elastic wave device of the present invention, Rayleigh mode spurious signals generated in a frequency band lower than the excitation mode used to obtain the characteristics, and higher-order mode spurious signals generated in a frequency band higher than the excitation mode, can be reduced. Attached Figure Description

[0013] Figure 1 This is a front view of the elastic wave device according to Embodiment 1.

[0014] Figure 2 It is the elastic wave device mentioned above. Figure 1 Sectional view along line X1-X1.

[0015] Figure 3 This is a coordinate graph showing the phase characteristics of the higher-order modes of the aforementioned elastic wave device.

[0016] Figure 4A This is a coordinate graph showing the phase characteristics of the aforementioned elastic wave device. Figure 4B This is a coordinate graph showing the phase characteristics of the Rayleigh mode of the aforementioned elastic wave device. Figure 4C This is a coordinate graph showing the phase characteristics of the main mode of the aforementioned elastic wave device.

[0017] Figures 5A-5C This is a contour plot showing the characteristics of the electromechanical coupling coefficient in the elastic wave device of Embodiment 2.

[0018] Figures 6A to 6C This is a contour plot showing the characteristics of TCF in the elastic wave device of Embodiment 3.

[0019] Figure 7 This is a cross-sectional view of the elastic wave device according to embodiment 4.

[0020] Figure 8A This is a coordinate graph showing the phase characteristics of the aforementioned elastic wave device. Figure 8B This is a coordinate graph showing the phase characteristics of the Rayleigh mode of the aforementioned elastic wave device. Figure 8C This is a coordinate graph showing the phase characteristics of the main mode of the aforementioned elastic wave device.

[0021] Figures 9A to 9C This is a contour plot showing the characteristics of the electromechanical coupling coefficient in the elastic wave device of Embodiment 5.

[0022] Figures 10A to 10C This is a contour plot showing the characteristics of TCF in the elastic wave device of Embodiment 6.

[0023] Figure 11 This is a cross-sectional view of the elastic wave device according to embodiment 7.

[0024] Figure 12This is a cross-sectional view of the elastic wave device according to embodiment 8.

[0025] Figure 13 It is a cross-sectional view of an elastic wave device with an intermediate layer inserted. Detailed Implementation

[0026] Hereinafter, the elastic wave device according to embodiments 1 to 8 will be described with reference to the accompanying drawings. The embodiments referred to in the following description, etc., are... Figure 1 , Figure 2 , Figure 7 , Figure 11 , Figure 12 and Figure 13 This is a schematic diagram. The size and thickness ratios of the components in the diagram may not necessarily reflect the actual size ratios.

[0027] (Implementation Method 1)

[0028] (1) Elastic wave device

[0029] The overall structure of the elastic wave device 1 of Embodiment 1 will be described with reference to the accompanying drawings.

[0030] like Figure 1 and Figure 2 As shown, the elastic wave device 1 of Embodiment 1 includes a support substrate 2, a laminate 3, a low-velocity diaphragm 4, a high-velocity diaphragm 5, and an IDT (Interdigital Transducer) electrode 6. Additionally, the elastic wave device 1 also includes two reflectors 7, a wiring section 8, and a protective film (not shown).

[0031] (2) Components of an elastic wave device

[0032] Hereinafter, the constituent elements of the elastic wave device 1 of Embodiment 1 will be described with reference to the accompanying drawings.

[0033] (2.1) Support base plate

[0034] like Figure 2 As shown, the support substrate 2 has a first main surface 21 and a second main surface 22 facing each other. The first main surface 21 and the second main surface 22 are facing each other in the thickness direction (first direction D1) of the support substrate 2. When viewed from above in the thickness direction (first direction D1) of the support substrate 2, the support substrate 2 is, for example, rectangular in shape. It should be noted that the support substrate 2 is not limited to a rectangular shape, and may also be square, for example.

[0035] In the support substrate 2, the sound speed of the bulk wave propagating in the support substrate 2 is higher than the sound speed of the elastic wave propagating in the first piezoelectric layer 3A and the second piezoelectric layer 3B. Here, the bulk wave propagating in the support substrate 2 is the bulk wave with the lowest sound speed among the multiple bulk waves propagating in the support substrate 2.

[0036] The support substrate 2 is, for example, a silicon substrate. The thickness of the support substrate 2 is preferably 10λ (λ: the wavelength of the elastic wave determined by the electrode finger spacing P1 described later) or more and 180 μm or less, for example, 120 μm. When the support substrate 2 is a silicon substrate, the orientation of the first main surface 21 of the support substrate 2 is, for example, the (100) surface, but is not limited thereto, for example, the (110) surface, the (111) surface, etc. The propagation orientation of the elastic wave can be set without being restricted by the orientation of the first main surface 21 of the support substrate 2.

[0037] The material of the support substrate 2 is not limited to silicon. The support substrate 2 may comprise at least one material selected from the group consisting of silicon, aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, sapphire, lithium tantalate, lithium niobate, quartz, bauxite, zirconium oxide, cordierite, mullite, block talc, forsterite, magnesium oxide, and diamond.

[0038] (2.2) Laminated body

[0039] like Figure 2 As shown, the laminate 3 includes a first piezoelectric layer 3A and a second piezoelectric layer 3B. Furthermore, the laminate 3 has a first main surface 31 and a second main surface 32. The first main surface 31 and the second main surface 32 are opposite each other in the thickness direction (first direction D1) of the supporting substrate 2. Here, the thickness of the laminate 3 is the thickness between the first main surface 31 and the second main surface 32. The first main surface 31 is the surface on the side of the IDT electrode 6 of the piezoelectric layer in the laminate 3, and the second main surface 32 is the surface on the side of the supporting substrate 2 of the piezoelectric layer in the laminate 3.

[0040] (2.3.1) First piezoelectric layer

[0041] like Figure 2 As shown, the first piezoelectric layer 3A is disposed on the support substrate 2 via the second piezoelectric layer 3B. More specifically, the first piezoelectric layer 3A is disposed on the first main surface 21 side of the support substrate 2 in the thickness direction (first direction D1) of the support substrate 2 via the second piezoelectric layer 3B, the low-velocity film 4 and the high-velocity film 5.

[0042] The first piezoelectric layer 3A is formed, for example, by Y-cutting X-propagating LiTaO3 piezoelectric single crystal. The Y-cutting X-propagating LiTaO3 piezoelectric single crystal is obtained by cutting a LiTaO3 single crystal along a plane with the Z-axis as the normal after rotating it θ1 [°] from the Y-axis to the Z-axis with the X-axis as the central axis, with the three crystal axes of the LiTaO3 piezoelectric single crystal set as the X-axis, Y-axis, and Z-axis. Furthermore, it is a single crystal in which surface acoustic waves propagate along the X-axis. Regarding the cutting angle of the first piezoelectric layer 3A, when the cutting angle is set to Γ1 [°] and the Euler angle of the first piezoelectric layer 3A is set to (… When θ1 and ψ1 are present, θ1 = Γ1 + 90°. Here, Γ1 is synonymous with Γ1 ± 180 × n. Here, n is a natural number. The first piezoelectric layer 3A is not limited to Y-cut X-propagated LiTaO3 piezoelectric single crystals; for example, it can also be Y-cut X-propagated LiTaO3 piezoelectric ceramics.

[0043] (2.3.2) Second piezoelectric layer

[0044] like Figure 2 As shown, the second piezoelectric layer 3B is disposed on the support substrate 2. "The second piezoelectric layer 3B is disposed on the support substrate 2" includes the case where the second piezoelectric layer 3B is disposed directly on the support substrate 2 without passing through other layers, and the case where the second piezoelectric layer 3B is disposed indirectly on the support substrate 2 through other layers.

[0045] exist Figure 2 In the example, the second piezoelectric layer 3B is indirectly disposed on the support substrate 2. More specifically, the second piezoelectric layer 3B is disposed on the first main surface 21 side of the support substrate 2 via a low-velocity film 4 and a high-velocity film 5 in the thickness direction (first direction D1) of the support substrate 2.

[0046] The second piezoelectric layer 3B is formed, for example, by Y-cutting X-propagating LiNbO3 piezoelectric single crystal. Y-cutting X-propagating LiNbO3 piezoelectric single crystal is obtained by cutting a LiNbO3 single crystal along a plane with the X-axis as the central axis and the Y-axis as the Z-axis, after rotating the LiNbO3 piezoelectric single crystal from the Y-axis to the Z-axis direction by θ2 [°]. Furthermore, it is a single crystal in which surface acoustic waves propagate along the X-axis direction. Regarding the cutting angle of the second piezoelectric layer 3B, when the cutting angle is set to Γ2 [°] and the Euler angle of the second piezoelectric layer 3B is set to (…),… When θ2 and ψ2 are present, θ2 = Γ2 + 90°. Here, Γ2 is synonymous with Γ2 ± 180 × n. Here, n is a natural number. The second piezoelectric layer 3B is not limited to Y-cut X-propagated LiNbO3 piezoelectric single crystals; for example, it can also be Y-cut X-propagated LiNbO3 piezoelectric ceramics.

[0047] (2.3.3) Total film thickness of the first piezoelectric layer and the second piezoelectric layer

[0048] The combined film thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is, for example, that of the electrode finger spacing P1 of the IDT electrode 6 (refer to...). Figure 1When the wavelength of the elastic wave is set to λ, it is 3.5λ or less. When the total thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 3.5λ or less, the Q value of the elastic wave device 1 becomes higher. Furthermore, by setting the total thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B to 2.5λ or less, the TCF (Temperature Coefficient of Frequency) can be reduced. Moreover, by setting the total thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B to 1.5λ or less, the adjustment of the sound velocity of the elastic wave becomes easier. For example, when the wavelength λ of the elastic wave is 2μm, the total thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 0.1λ (200nm). It should be noted that the total thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is not limited to 3.5λ or less, and can also be greater than 3.5λ.

[0049] However, although the Q value increases as described above when the combined thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 3.5λ or less, higher-order modes are generated. In the elastic wave device 1, a low-velocity film 4 and a high-velocity film 5 are provided, so that even when the combined thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 3.5λ or less, higher-order modes are reduced.

[0050] (2.3.4) Modes of elastic waves propagating in the first and second piezoelectric layers

[0051] In the elastic wave device 1, the modes of the elastic wave propagating in the first piezoelectric layer 3A include longitudinal waves, SH waves, or SV waves, or modes obtained by combining them. In the elastic wave device 1, the mode with SH waves as the main component is used as the main mode. Higher-order modes refer to stray modes generated at higher frequencies than the main mode of the elastic wave propagating in the first piezoelectric layer 3A. Regarding whether the mode of the elastic wave propagating in the first piezoelectric layer 3A is "the mode with SH waves as the main component is used as the main mode", for example, it can be confirmed by using parameters such as the first piezoelectric layer 3A (material, Euler angle, and thickness, etc.), the second piezoelectric layer 3B (material, Euler angle, and thickness, etc.), the IDT electrode 6 (material, thickness, and electrode finger spacing P1, etc.), the low-velocity membrane 4 (material, thickness, etc.), and the high-velocity membrane 5 (material, thickness, etc.), and by analyzing the displacement distribution and deformation using the finite element method. The Euler angle of the first piezoelectric layer 3A can be obtained through analysis.

[0052] In the elastic wave device 1, the modes of the elastic wave propagating in the second piezoelectric layer 3B include longitudinal waves, SH waves, or SV waves, or modes obtained by combining them. In the elastic wave device 1, the mode with SH waves as the main component is used as the main mode. Higher-order modes refer to stray modes generated at higher frequencies than the main mode of the elastic wave propagating in the second piezoelectric layer 3B. Regarding whether the mode of the elastic wave propagating in the second piezoelectric layer 3B is "the mode with SH waves as the main component is used as the main mode", for example, it can be confirmed by using parameters such as the first piezoelectric layer 3A (material, Euler angle, and thickness, etc.), the second piezoelectric layer 3B (material, Euler angle, and thickness, etc.), the IDT electrode 6 (material, thickness, and electrode finger spacing P1, etc.), the low-velocity membrane 4 (material, thickness, etc.), and the high-velocity membrane 5 (material, thickness, etc.), and by analyzing the displacement distribution and deformation using the finite element method. The Euler angles of the second piezoelectric layer 3B can be obtained through analysis.

[0053] It should be noted that in the elastic wave device 1, the mode with SH wave as the main component is not limited to being used as the main mode in both the first piezoelectric layer 3A and the second piezoelectric layer 3B. It is also possible that the mode with SH wave as the main component is used only in the first piezoelectric layer 3A, or only in the second piezoelectric layer 3B. In short, the mode with SH wave as the main component can be used as the main mode in at least one of the first piezoelectric layer 3A and the second piezoelectric layer 3B.

[0054] (2.4) Low-velocity membrane

[0055] like Figure 2 As shown, the low-velocity film 4 is disposed on the support substrate 2. "The low-velocity film 4 is disposed on the support substrate 2" includes the case where the low-velocity film 4 is disposed directly on the support substrate 2 without passing through other layers and the case where the low-velocity film 4 is disposed indirectly on the support substrate 2 through other layers.

[0056] exist Figure 2 In this example, the low-velocity sound film 4 is disposed between the support substrate 2 and the second piezoelectric layer 3B in the thickness direction (first direction D1) of the support substrate 2. More specifically, the low-velocity sound film 4 is formed on the first main surface 21 side of the support substrate 2 via the high-velocity sound film 5. The low-velocity sound film 4 is a film in which the velocity of the bulk wave propagating in the low-velocity sound film 4 is lower than the velocity of the bulk wave propagating in the first piezoelectric layer 3A and the second piezoelectric layer 3B.

[0057] By placing a low-velocity sound membrane 4 between the support substrate 2 and the second piezoelectric layer 3B, the sound velocity of the elastic wave is reduced. Elastic waves inherently possess the property of concentrating energy in a low-velocity medium. Therefore, the energy of the elastic wave can be effectively contained within the second piezoelectric layer 3B and within the IDT electrode 6 where the elastic wave is excited. As a result, compared to the case without the low-velocity sound membrane 4, losses can be reduced and the Q value of the elastic wave device 1 can be increased.

[0058] The material of the low-velocity membrane 4 is, for example, silicon oxide. It should be noted that the material of the low-velocity membrane 4 is not limited to silicon oxide, and may also be glass, silicon oxynitride, tantalum oxide, a compound obtained by adding fluorine, carbon or boron to silicon oxide, or a material with the above-mentioned materials as the main components.

[0059] When the low-velocity film 4 is made of silicon oxide, the temperature characteristics can be improved. Lithium tantalate has a negative temperature constant, while silicon oxide has a positive temperature constant. Therefore, in the elastic wave device 1, the absolute value of TCF can be reduced.

[0060] When the wavelength of the elastic wave, determined by the electrode finger spacing P1, is set to λ, the thickness of the low-velocity film 4 is preferably 2.0λ or less. For example, when the wavelength λ of the elastic wave is 2 μm, the thickness of the low-velocity film 4 is 0.2λ (400 nm). By setting the thickness of the low-velocity film 4 to 2.0λ or less, film stress can be reduced. As a result, warpage of the silicon wafer that forms the basis of the supporting substrate 2 during the manufacture of the elastic wave device 1 can be reduced, thereby improving the yield and stabilizing the characteristics.

[0061] Furthermore, the elastic wave device 1 may include, for example, a bonding layer sandwiched between the low-velocity membrane 4 and the second piezoelectric layer 3B. This improves the adhesion between the low-velocity membrane 4 and the second piezoelectric layer 3B. The bonding layer may be made of, for example, resin (epoxy resin, polyimide resin, etc.), metal, etc. Alternatively, the elastic wave device 1 is not limited to a bonding layer; a dielectric film may also be disposed between the low-velocity membrane 4 and the second piezoelectric layer 3B, on the second piezoelectric layer 3B, or under the low-velocity membrane 4.

[0062] (2.5) High-speed sound membrane

[0063] like Figure 2 As shown, the hypersonic membrane 5 is disposed on the support substrate 2. "The hypersonic membrane 5 is disposed on the support substrate 2" includes the case where the hypersonic membrane 5 is disposed directly on the support substrate 2 without passing through other layers and the case where the hypersonic membrane 5 is disposed indirectly on the support substrate 2 through other layers.

[0064] exist Figure 2In this example, the high-velocity acoustic film 5 is disposed between the support substrate 2 and the low-velocity acoustic film 4 in the thickness direction (first direction D1) of the support substrate 2. More specifically, the high-velocity acoustic film 5 is formed on the first main surface 21 side of the support substrate 2. The high-velocity acoustic film 5 is a film in which the velocity of the bulk wave propagating in the high-velocity acoustic film 5 is higher than the velocity of the elastic wave propagating in the first piezoelectric layer 3A and the second piezoelectric layer 3B.

[0065] The thickness of the hypersonic membrane 5 is, for example, 200 nm, 300 nm, 400 nm, or 600 nm. For example, when the wavelength λ of the elastic wave is 2 μm, the thickness of the hypersonic membrane 5 is 0.3λ (600 nm). Regarding the thickness of the hypersonic membrane 5, since the hypersonic membrane 5 has the function of confining the elastic wave to the first piezoelectric layer 3A, the second piezoelectric layer 3B, and the low-velocity membrane 4, the thicker the hypersonic membrane 5, the better.

[0066] The function of the hypersonic membrane 5 is to suppress the leakage of energy of the main mode elastic wave to structures lower than the hypersonic membrane 5. In the elastic wave device 1, when the thickness of the hypersonic membrane 5 is sufficiently thick, the energy of the main mode elastic wave is distributed throughout the first piezoelectric layer 3A, the second piezoelectric layer 3B, and the low-velocity membrane 4, and also a portion on the low-velocity membrane 4 side of the hypersonic membrane 5, but not on the supporting substrate 2. The mechanism by which the hypersonic membrane 5 blocks the elastic wave is the same as that for non-leaking SH waves, i.e., Love wave type surface waves, as described, for example, in the literature "Introduction to Simulation Technology of Surface Acoustic Wave Devices", Kenya Hashimoto, Realize Co., Ltd., pp. 26-28. This mechanism differs from the mechanism of blocking elastic waves using a Bragg reflector based on an acoustic multilayer membrane.

[0067] The material of the hypersonic membrane 5 is, for example, silicon nitride. It should be noted that the material of the hypersonic membrane 5 is not limited to silicon nitride, and may also be at least one material selected from the group consisting of diamond-like carbon, aluminum nitride, aluminum oxide, silicon carbide, silicon, sapphire, piezoelectric materials (lithium tantalate, lithium niobate, or quartz), bauxite, zirconium oxide, cordierite, mullite, block talc, forsterite, magnesium oxide, and diamond. The material of the hypersonic membrane 5 may also be a material with any of the above-mentioned materials as its main component, or a material with a mixture of any of the above-mentioned materials as its main component.

[0068] (2.6) IDT electrode

[0069] like Figure 1 and Figure 2 As shown, the IDT electrode 6 is disposed on the first piezoelectric layer 3A. More specifically, the IDT electrode 6 is formed on the first main surface 31 of the laminate 3 in the thickness direction (first direction D1) of the support substrate 2.

[0070] like Figure 1As shown, the IDT electrode 6 has two electrodes 61. In other words, the IDT electrode 6 has two busbars 62 and two sets of electrode fingers 63. More specifically, the IDT electrode 6 has a first electrode 61A and a second electrode 61B. The first electrode 61A and the second electrode 61B are both conductive. The first electrode 61A and the second electrode 61B are separated from each other and electrically insulated from each other.

[0071] The first electrode 61A is comb-shaped when viewed from the thickness direction (first direction D1) of the support substrate 2. The first electrode 61A has a first busbar 62A and a plurality of first electrode fingers 63A. The first busbar 62A is a conductor portion for making the plurality of first electrode fingers 63A have the same potential (equipotential).

[0072] The second electrode 61B is comb-shaped when viewed from the thickness direction (first direction D1) of the support substrate 2. The second electrode 61B has a second busbar 62B and a plurality of second electrode fingers 63B. The second busbar 62B is a conductor portion used to make the plurality of second electrode fingers 63B have the same potential (equipotential). In the IDT electrode 6, in the third direction D3, the first busbar 62A and the second busbar 62B are opposite each other.

[0073] Multiple first electrode fingers 63A are connected to the first busbar 62A and extend toward the second busbar 62B. The multiple first electrode fingers 63A are integrally formed with the first busbar 62A and are separate from the second busbar 62B.

[0074] Multiple second electrode fingers 63B are connected to the second busbar 62B and extend toward the first busbar 62A. The multiple second electrode fingers 63B are integrally formed with the second busbar 62B and are separate from the first busbar 62A.

[0075] IDT electrode 6 is, for example, a standard type of IDT electrode. The IDT electrode 6 will be described in more detail below.

[0076] The first busbar 62A and the second busbar 62B of the IDT electrode 6 are elongated strips with the second direction D2 defined as the long side direction. In the IDT electrode 6, the first busbar 62A and the second busbar 62B are opposite each other in the third direction D3. The second direction D2 is orthogonal to the thickness direction (first direction D1) of the support substrate 2. The third direction D3 is orthogonal to both the thickness direction (first direction D1) and the second direction D2 of the support substrate 2.

[0077] Multiple first electrode fingers 63A are connected to a first busbar 62A and extend toward a second busbar 62B. Here, the multiple first electrode fingers 63A extend from the first busbar 62A along a third direction toward D3. The leading ends of the multiple first electrode fingers 63A are separated from the second busbar 62B. For example, the multiple first electrode fingers 63A are of the same length.

[0078] Multiple second electrode fingers 63B are connected to a second busbar 62B and extend toward a first busbar 62A. Here, the multiple second electrode fingers 63B extend from the second busbar 62B along a third direction toward D3. The leading ends of the multiple second electrode fingers 63B are separated from the first busbar 62A. For example, the multiple second electrode fingers 63B are of the same length. Figure 1 In the example, the lengths of the multiple second electrode fingers 63B are the same as the lengths of the multiple first electrode fingers 63A.

[0079] In the IDT electrode 6, multiple first electrode fingers 63A and multiple second electrode fingers 63B are arranged alternately, one by one, in the second direction D2. Therefore, adjacent first electrode fingers 63A and second electrode fingers 63B are separated by a distance S1. A group of electrode fingers 63 comprising multiple first electrode fingers 63A and multiple second electrode fingers 63B can be a structure in which the multiple first electrode fingers 63A and multiple second electrode fingers 63B are arranged alternately in the second direction D2, or it can be a structure in which the multiple first electrode fingers 63A and multiple second electrode fingers 63B are not arranged alternately. For example, regions where the first electrode fingers 63A and second electrode fingers 63B are arranged alternately and regions where two of the first electrode fingers 63A or second electrode fingers 63B are arranged in the second direction D2 can also be mixed.

[0080] Multiple first electrode fingers 63A and multiple second electrode fingers 63B are alternately inserted. Furthermore, when viewed from the direction of elastic wave propagation, the length of overlap between the first electrode fingers 63A and the second electrode fingers 63B is called the cross width W1. That is, the IDT electrode 6 has a cross region defined by the multiple first electrode fingers 63A and the multiple second electrode fingers 63B. The cross region is the area between the envelope of the leading edge of the multiple first electrode fingers 63A and the envelope of the leading edge of the multiple second electrode fingers 63B. The IDT electrode 6 excites elastic waves in the first piezoelectric layer 3A and the second piezoelectric layer 3B within the cross region.

[0081] It should be noted that the IDT electrode 6 is not limited to a standard IDT electrode; for example, it can also be an IDT electrode with apodization weighting or a tilted IDT electrode. In the IDT electrode with apodization weighting, the cross width increases as it approaches the center from one end in the direction of elastic wave propagation, and decreases as it approaches the other end from the center in the direction of elastic wave propagation.

[0082] like Figure 1 As shown, the electrode finger spacing P1 of the IDT electrode 6 is defined by the distance between the center lines of two adjacent first electrode fingers 63A among a plurality of first electrode fingers 63A, or the distance between the center lines of two adjacent second electrode fingers 63B among a plurality of second electrode fingers 63B. The distance between the center lines of two adjacent second electrode fingers 63B is the same as the distance between the center lines of two adjacent first electrode fingers 63A.

[0083] In the IDT electrode 6 of the elastic wave device 1 in Embodiment 1, as an example, the number of first electrode fingers 63A and second electrode fingers 63B is 100. That is, as an example, the IDT electrode 6 has 100 first electrode fingers 63A and 100 second electrode fingers 63B.

[0084] The material of the IDT electrode 6 is aluminum (Al), copper (Cu), platinum (Pt), gold (Au), silver (Ag), titanium (Ti), nickel (Ni), chromium (Cr), molybdenum (Mo), or tungsten (W), or an alloy of any of these metals as the main component, or a suitable metallic material. Alternatively, the IDT electrode 6 may also have a structure consisting of multiple metal films made of these metals or alloys stacked together.

[0085] (2.7) Reflector

[0086] like Figure 1 As shown, two reflectors 7 are disposed on the first piezoelectric layer 3A. More specifically, the two reflectors 7 are formed on the first main surface 31 of the first piezoelectric layer 3A in the thickness direction (first direction D1) of the supporting substrate 2. The two reflectors 7 are conductive.

[0087] Two reflectors 7 are respectively disposed on one side and the other side of the IDT electrode 6 in the direction (second direction D2) along the propagation direction of the elastic wave of the elastic wave device 1. In other words, in the second direction D2, the IDT electrode 6 is located between the two reflectors 7. Each reflector 7 is, for example, a short-circuit grating. Each reflector 7 reflects the elastic wave.

[0088] Each of the two reflectors 7 has a plurality of electrode fingers 71, one end of which is short-circuited to the other and the other end of which is short-circuited to the other. In each of the two reflectors 7, for example, the number of electrode fingers is 20.

[0089] Each reflector 7 is made of a suitable metallic material, such as aluminum (Al), copper (Cu), platinum (Pt), gold (Au), silver (Ag), titanium (Ti), nickel (Ni), chromium (Cr), molybdenum (Mo), or tungsten (W), or an alloy of any of these metals as the main component. Alternatively, each reflector 7 may have a structure consisting of multiple metal films made of these metals or alloys stacked together.

[0090] In the elastic wave device 1, if each reflector 7 and IDT electrode 6 are made of the same material and have the same thickness, each reflector 7 and IDT electrode 6 can be formed by the same process during the manufacture of the elastic wave device 1.

[0091] It should be noted that in the elastic wave device 1 of embodiment 1, each reflector 7 is a short-circuit grating, but each reflector 7 is not limited to a short-circuit grating. For example, it can also be an open grating, a positive and negative reflection type grating, or a grating obtained by combining a short-circuit grating and an open grating.

[0092] (2.8) Wiring Department

[0093] like Figure 1 As shown, the wiring portion 8 is disposed in the first piezoelectric layer 3A. More specifically, the wiring portion 8 is formed on the first main surface 31 of the laminate 3 in the thickness direction (first direction D1) of the support substrate 2. The wiring portion 8 is conductive.

[0094] The wiring section 8 includes a first wiring section 81 and a second wiring section 82. The first wiring section 81 is connected to the first busbar 62A of the IDT electrode 6. The second wiring section 82 is connected to the second busbar 62B of the IDT electrode 6. The first wiring section 81 and the second wiring section 82 are separate from each other and electrically insulated from each other.

[0095] The first wiring portion 81 extends from the first busbar 62A to the side opposite to the side of the plurality of first electrode fingers 63A. The first wiring portion 81 may be formed to repeat a portion of the first busbar 62A in the thickness direction (first direction D1) of the support substrate 2, or it may be formed integrally with the first busbar 62A using the same material and the same thickness as the first busbar 62A.

[0096] The second wiring portion 82 extends from the second busbar 62B to the side opposite to the side of the plurality of second electrode fingers 63B. The second wiring portion 82 may be formed to repeat a portion of the second busbar 62B in the thickness direction (first direction D1) of the support substrate 2, or it may be formed integrally with the second busbar 62B using the same material and the same thickness as the second busbar 62B.

[0097] The wiring section 8 is made of a suitable metallic material, such as aluminum (Al), copper (Cu), platinum (Pt), gold (Au), silver (Ag), titanium (Ti), nickel (Ni), chromium (Cr), molybdenum (Mo), or tungsten (W), or an alloy of any of these metals as the main component. Alternatively, the wiring section 8 may have a structure in which multiple metal films composed of these metals or alloys are stacked.

[0098] (2.9) Protective film

[0099] A protective film (not shown) is formed on the first piezoelectric layer 3A. The protective film covers the IDT electrode 6, each reflector 7 and wiring portion 8 on the first main surface 31 of the laminate 3, as well as a portion of the first main surface 31 of the laminate 3.

[0100] The protective film is made of materials such as silicon oxide. It should be noted that the material of the protective film is not limited to silicon oxide; it can also be silicon nitride, for example. The protective film is not limited to a single-layer structure; it can also be a multi-layer structure with two or more layers.

[0101] (3) Characteristics of elastic wave devices

[0102] Hereinafter, the characteristics of the elastic wave device 1 of Embodiment 1 will be described in comparison with the elastic wave device of the comparative example, with reference to the accompanying drawings.

[0103] First, in the elastic wave device of the comparative example, the combined film thickness ratio of the first piezoelectric layer 3A to the second piezoelectric layer 3B is 0.66λ, therefore, as Figure 3 As shown, higher-order modes have larger phase characteristics.

[0104] On the other hand, in the elastic wave device 1 of Embodiment 1, the combined film thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 0.66λ or less. Therefore, as Figure 3 As shown, the phase characteristics of higher-order modes become smaller.

[0105] It should be noted that, to obtain Figure 3 The conditions for the elastic wave device 1 with the following characteristics are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon. The second Euler angle θ1 of the first piezoelectric layer 3A is 130°, and the second Euler angle θ2 of the second piezoelectric layer 3B is 50°. With the ratio (T1 / T2) of the thickness T1 of the first piezoelectric layer 3A to the thickness T2 of the second piezoelectric layer 3B fixed at 3, the total film thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is varied.

[0106] However, as Figure 3 As shown, the combined thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is preferably 0.33λ or less. This allows for a further reduction in the phase characteristics of higher-order modes.

[0107] Furthermore, the combined thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is more preferably 0.2λ or less. This allows for a further reduction in the phase characteristics of higher-order modes.

[0108] It should be noted that it is also possible to do as follows: Figure 13 As shown in the elastic wave device 1c, an intermediate layer 3C comprising silicon oxide or silicon nitride is inserted between the first piezoelectric layer 3A and the second piezoelectric layer 3B. The thickness of the intermediate layer is, for example, 1 to 30 nm. In particular, when the intermediate layer is silicon oxide, the frequency-temperature characteristics can be improved.

[0109] Figures 4A to 4C The phase characteristics A1 of the elastic wave device 1 of Embodiment 1 and the phase characteristics A2 and A3 of the elastic wave devices of Comparative Examples 1 and 2 are shown. Figure 4B yes Figure 4A A magnified view of the low-frequency band (Rayleigh spurs) in the image. Figure 4C yes Figure 4A An enlarged view of the main mode in the image.

[0110] In the elastic wave device 1 of Embodiment 1, the first piezoelectric layer 3A is a lithium tantalate piezoelectric layer, and the second piezoelectric layer 3B is a lithium niobate piezoelectric layer. In the elastic wave device of Comparative Example 1, the piezoelectric layer is solely a lithium tantalate piezoelectric layer. In the elastic wave device of Comparative Example 2, the piezoelectric layer is solely a lithium niobate piezoelectric layer. When the Euler angles of the first piezoelectric layer 3A are set to (0, θ1, 0), and the Euler angles of the second piezoelectric layer 3B are set to (0, θ2, 0), Figures 4A to 4C Phase characteristic A1 in the elastic wave device 1 of Embodiment 1 is the phase characteristic when the second Euler angle θ1 is 0° and the second Euler angle θ2 is -70°. Phase characteristic A2 in the elastic wave device of Comparative Example 1 is the phase characteristic when the second Euler angle θ1 is 0°. Phase characteristic A3 in the elastic wave device of Comparative Example 2 is the phase characteristic when the second Euler angle θ2 is -70°.

[0111] like Figure 4A As shown, the phase characteristic A1 of the elastic wave device 1 in Embodiment 1 is improved compared with the phase characteristics A2 and A3 of the elastic wave devices in Comparative Examples 1 and 2 in frequency bands other than the main mode frequency band.

[0112] Especially Figure 4B As shown, at a frequency lower than the main mode's frequency band, the elastic wave device 1 of Embodiment 1, compared to the elastic wave devices of Comparative Examples 1 and 2, can reduce Rayleigh mode spurious emissions. On the other hand, as Figure 4C As shown, in the elastic wave device 1 of Embodiment 1, the main mode characteristics are also obtained to the same extent as those of the elastic wave devices of Comparative Examples 1 and 2.

[0113] It should be noted that, to obtain Figures 4A to 4CThe conditions for the elastic wave device 1 with phase characteristic A1 are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the first piezoelectric layer 3A is 0.05λ, the thickness of the second piezoelectric layer 3B is 0.15λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon. In the elastic wave device of Comparative Example 1, the thickness of the IDT electrode is 0.05λ, the thickness of the first piezoelectric layer is 0.2λ, the thickness of the low-velocity film is 0.15λ, and the thickness of the high-velocity film is 0.15λ. The material of the IDT electrode is aluminum, the material of the low-velocity film is silicon oxide, the material of the high-velocity film is silicon nitride, and the material of the support substrate is silicon. In the elastic wave device of Comparative Example 2, the thickness of the IDT electrode is 0.05λ, the thickness of the second piezoelectric layer is 0.2λ, the thickness of the low-velocity film is 0.15λ, and the thickness of the high-velocity film is 0.15λ. The material of the IDT electrode is aluminum, the material of the low-velocity film is silicon oxide, the material of the high-velocity film is silicon nitride, and the material of the support substrate is silicon.

[0114] (4) Effect

[0115] In the elastic wave device 1 of Embodiment 1, the thickness of the stack 3, which includes a first piezoelectric layer 3A (lithium tantalate piezoelectric layer) and a second piezoelectric layer 3B (lithium niobate piezoelectric layer), is 0.66λ or less. Here, the thickness of the stack 3 refers to the thickness between the first main surface 31 and the second main surface 32. The first main surface 31 is the surface on the side of the IDT electrode 6 of the piezoelectric layer in the stack 3, and the second main surface 32 is the surface on the side of the support substrate 2 of the piezoelectric layer in the stack 3. As a result, Rayleigh mode spurious emissions generated in a frequency band lower than the excitation mode used to obtain the characteristics, and higher-order mode spurious emissions generated in a frequency band higher than the excitation mode, can be reduced. In addition, when the elastic wave device 1 is used as a filter, Rayleigh mode spurious emissions generated in the low-frequency band of the filter's passband, and higher-order mode spurious emissions generated in the high-frequency band of the filter's passband, can be reduced.

[0116] In the elastic wave device 1 of Embodiment 1, a first piezoelectric layer 3A (lithium tantalate piezoelectric layer) is stacked on the side of the IDT electrode 6, and a second piezoelectric layer 3B (lithium niobate piezoelectric layer) is stacked on the side of the support substrate 2. This improves the temperature characteristics.

[0117] In the elastic wave device 1 of Embodiment 1, at least one of the first piezoelectric layer 3A (lithium tantalate piezoelectric layer) and the second piezoelectric layer 3B (lithium niobate piezoelectric layer) is rotated Y-cut. This allows for more efficient excitation of SH waves and is easier to use.

[0118] In the elastic wave device 1 of Embodiment 1, the first piezoelectric layer 3A (lithium tantalate piezoelectric layer) and the second piezoelectric layer 3B (lithium niobate piezoelectric layer) are rotated Y-cut. As a result, SH waves can be excited more efficiently.

[0119] In the elastic wave device 1 of Embodiment 1, a low-velocity sound membrane 4 is provided between the support substrate 2 and the laminate 3 in the thickness direction (first direction D1) of the support substrate 2. As a result, the Q value of the elastic wave device 1 can be improved.

[0120] In the elastic wave device 1 of Embodiment 1, a high-velocity sound membrane 5 is provided between the support substrate 2 and the low-velocity sound membrane 4 in the thickness direction (first direction D1) of the support substrate 2. This allows for a further improvement in the Q value of the elastic wave device 1.

[0121] (5) Variations

[0122] Hereinafter, a variation of Implementation 1 will be described.

[0123] In the elastic wave device 1, other films besides the high-velocity membrane 5, the low-velocity membrane 4, the first piezoelectric layer 3A, and the second piezoelectric layer 3B may also include a bonding layer, a dielectric membrane, etc.

[0124] In the modified elastic wave device 1 described above, it also achieves the same effect as the elastic wave device 1 in Embodiment 1.

[0125] (Implementation Method 2)

[0126] The elastic wave device 1 of Embodiment 2 differs from the elastic wave device 1 of Embodiment 1 in that its electromechanical coupling coefficient is 4.0% or higher. It should be noted that, regarding the elastic wave device 1 of Embodiment 2, the same reference numerals are used for the same constituent elements as those in the elastic wave device 1 of Embodiment 1, and descriptions are omitted.

[0127] (1) Structure

[0128] In Embodiment 2, the elastic wave device 1 sets the Euler angles of the first piezoelectric layer 3A and the second piezoelectric layer 3B to an electromechanical coupling coefficient of 4.0% or more. When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is 0° or more and less than 180°, the electromechanical coupling coefficient is expressed by the following equation (1). When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is -180° or more and less than 0°, the electromechanical coupling coefficient is expressed by the following equation (2). Equations (1) and (2) represent formulas that make the electromechanical coupling coefficient 100 times. The second Euler angle θ1 satisfies θ1=θ1+180°×n (n=0, ±1, ±2). It should be noted that, regarding the first piezoelectric layer 3A and the second piezoelectric layer 3B of Embodiment 2, the description of the same structure and function as that of the first piezoelectric layer 3A and the second piezoelectric layer 3B of Embodiment 1 is omitted.

[0129] [Formula 1]

[0130]

[0131] [Formula 2]

[0132]

[0133] (2) Characteristics of elastic wave devices

[0134] Figures 5A-5C The characteristics of the electromechanical coupling coefficient are shown when the ratio (T1 / T2) of the thickness T1 of the first piezoelectric layer 3A to the thickness T2 of the second piezoelectric layer 3B is changed. Figures 5A-5C In each diagram, the "Euler angles of the first layer" is the second Euler angle θ1 in the Euler angles (0, θ1, 0) of the first piezoelectric layer 3A, and the "Euler angles of the second layer" is the second Euler angle θ2 in the Euler angles (0, θ2, 0) of the second piezoelectric layer 3B. This yields... Figures 5A-5C The conditions for the elastic wave device 1 with electromechanical coupling coefficient characteristics are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon.

[0135] Figure 5AThe characteristics of the electromechanical coupling coefficient are shown when the ratio (T1 / T2) is 0.33. For example, the thickness T1 of the first piezoelectric layer 3A is 0.05λ, and the thickness T2 of the second piezoelectric layer 3B is 0.15λ. By selecting a combination of the second Euler angles θ1 and θ2 such that the electromechanical coupling coefficient is 4.0% or higher, good characteristics can be obtained.

[0136] Figure 5B The characteristics of the electromechanical coupling coefficient are shown when the ratio (T1 / T2) is 1. For example, the thickness T1 of the first piezoelectric layer 3A and the thickness T2 of the second piezoelectric layer 3B are both 0.10λ. Similar to the case where the ratio (T1 / T2) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the electromechanical coupling coefficient is 4.0% or higher.

[0137] Figure 5C The characteristics of the electromechanical coupling coefficient are shown when the ratio (T1 / T2) is 3. For example, the thickness T1 of the first piezoelectric layer 3A is 0.15λ, and the thickness T2 of the second piezoelectric layer 3B is 0.05λ. Similar to the case where the ratio (T1 / T2) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the electromechanical coupling coefficient is 4.0% or higher.

[0138] (3) Effect

[0139] In the elastic wave device 1 of Embodiment 2, the electromechanical coupling coefficient is 4.0% or higher. This allows for efficient excitation of the main mode, which is dominated by SH waves, resulting in excellent characteristics. It should be noted that, as described above, equations (1) and (2) express the calculation formulas for the electromechanical coupling coefficient as percentages. Therefore, the second Euler angle θ1 and the second Euler angle θ2 are values ​​where the electromechanical coupling coefficient expressed by equations (1) and (2) is 4.0% or higher.

[0140] (Implementation Method 3)

[0141] The elastic wave device 1 of Embodiment 3 differs from the elastic wave device 1 of Embodiment 1 in that the absolute value of TCF is below 20 ppm / ℃. It should be noted that, regarding the elastic wave device 1 of Embodiment 3, the same reference numerals are used for the same components as those in the elastic wave device 1 of Embodiment 1, and descriptions are omitted.

[0142] (1) Structure

[0143] In Embodiment 3, the elastic wave device 1 sets the Euler angles of the first piezoelectric layer 3A and the second piezoelectric layer 3B such that the absolute value of the TCF is 20 ppm / ℃ or less. When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is 0° or more and less than 180°, the TCF is expressed by the following equation (5). When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is -180° or more and less than 0°, the TCF is expressed by the following equation (6). It should be noted that the description of the same structure and function as the first piezoelectric layer 3A and the second piezoelectric layer 3B in Embodiment 3 is omitted for the purposes of Embodiment 1.

[0144] [Formula 3]

[0145]

[0146] [Formula 4]

[0147]

[0148] (2) Characteristics of elastic wave devices

[0149] Figures 6A to 6C The characteristics of the TCF are shown when the ratio (T1 / T2) of the thickness T1 of the first piezoelectric layer 3A to the thickness T2 of the second piezoelectric layer 3B is changed. Figures 6A to 6C In each diagram, the "Euler angles of the first layer" is the second Euler angle θ1 in the Euler angles (0, θ1, 0) of the first piezoelectric layer 3A, and the "Euler angles of the second layer" is the second Euler angle θ2 in the Euler angles (0, θ2, 0) of the second piezoelectric layer 3B. This yields... Figures 6A to 6C The conditions for the elastic wave device 1 with TCF characteristics are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon.

[0150] Figure 6AThe characteristics of the TCF are shown when the ratio (T1 / T2) is 0.33. For example, the thickness T1 of the first piezoelectric layer 3A is 0.05λ, and the thickness T2 of the second piezoelectric layer 3B is 0.15λ. By selecting a combination of the second Euler angles θ1 and θ2 such that the TCF falls within the range of -20 ppm / ℃ to 20 ppm / ℃, good characteristics can be obtained. More preferably, a combination of the second Euler angles θ1 and θ2 is selected such that the TCF falls within the range of -10 ppm / ℃ to 10 ppm / ℃. This results in even better characteristics.

[0151] Figure 6B The characteristics of the TCF are shown when the ratio (T1 / T2) is 1. For example, the thickness T1 of the first piezoelectric layer 3A and the thickness T2 of the second piezoelectric layer 3B are both 0.10λ. Similar to the case where the ratio (T1 / T2) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the TCF is in the range of -20 ppm / ℃ or higher and 20 ppm / ℃ or lower. More preferably, a combination of the second Euler angles θ1 and θ2 is selected such that the TCF is in the range of -10 ppm / ℃ or higher and 10 ppm / ℃ or lower. Thus, even better characteristics can be obtained.

[0152] Figure 6C The characteristics of the TCF are shown when the ratio (T1 / T2) is 3. For example, the thickness T1 of the first piezoelectric layer 3A is 0.15λ, and the thickness T2 of the second piezoelectric layer 3B is 0.05λ. Similar to the case where the ratio (T1 / T2) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the TCF falls within the range of -20 ppm / ℃ to 20 ppm / ℃. More preferably, a combination of the second Euler angles θ1 and θ2 is selected such that the TCF falls within the range of -10 ppm / ℃ to 10 ppm / ℃. This results in even better characteristics.

[0153] (3) Effect

[0154] In the elastic wave device 1 of Embodiment 3, the absolute value of TCF is in the range of 20 ppm / ℃ or less. Therefore, a good TCF can be achieved.

[0155] In the elastic wave device 1 of Embodiment 3, the absolute value of TCF is in the range of 10 ppm / ℃ or less. Therefore, a better TCF can be achieved.

[0156] (Implementation Method 4)

[0157] like Figure 7As shown, the elastic wave device 1 of Embodiment 4 differs from the elastic wave device 1 of Embodiment 1 in that the first piezoelectric layer 3A and the second piezoelectric layer 3B are interchanged (see Figure 1). Figure 2 (Different.) It should be noted that, regarding the elastic wave device 1 of Embodiment 4, the same markings are used for the same constituent elements as those of the elastic wave device 1 of Embodiment 1, and the descriptions are omitted.

[0158] (1) Structure

[0159] In the elastic wave device 1 of embodiment 4, such as Figure 7 As shown, the first piezoelectric layer 3A and the second piezoelectric layer 3B have been interchanged. It should be noted that the elastic wave device 1 of Embodiment 4, like the elastic wave device 1 of Embodiment 1, includes a support substrate 2, a first piezoelectric layer 3A, a second piezoelectric layer 3B, a low-velocity film 4, a high-velocity film 5, an IDT electrode 6, two reflectors 7, and a wiring section 8.

[0160] (2) Characteristics of elastic wave devices

[0161] Hereinafter, the characteristics of the elastic wave device 1 of Embodiment 4 will be described with reference to the accompanying drawings in comparison with the elastic wave devices of Comparative Examples 1 and 2.

[0162] Figures 8A to 8C The phase characteristics B1 of the elastic wave device 1 of Embodiment 4 and the phase characteristics B2 and B3 of the elastic wave devices of Comparative Examples 1 and 2 are shown. Figure 8B yes Figure 8A A magnified view of the low-frequency band (Rayleigh spurs) in the image. Figure 8C yes Figure 8A An enlarged view of the main mode in the image.

[0163] In the elastic wave device 1 of Embodiment 4, the first piezoelectric layer 3A is a lithium tantalate piezoelectric layer, and the second piezoelectric layer 3B is a lithium niobate piezoelectric layer. The elastic wave device of Comparative Example 1 is an elastic wave device whose piezoelectric layer is solely a lithium tantalate piezoelectric layer. The elastic wave device of Comparative Example 2 is an elastic wave device whose piezoelectric layer is solely a lithium niobate piezoelectric layer. When the Euler angles of the first piezoelectric layer 3A are set to (0, θ1, 0), and the Euler angles of the second piezoelectric layer 3B are set to (0, θ2, 0), Figures 8A to 8C Phase characteristic B1 in the elastic wave device 1 of Embodiment 4 is the phase characteristic when the second Euler angle θ1 is 130° and the second Euler angle θ2 is 50°. Phase characteristic B2 in the elastic wave device of Comparative Example 1 is the phase characteristic when the second Euler angle θ1 is 130°. Phase characteristic B3 in the elastic wave device of Comparative Example 2 is the phase characteristic when the second Euler angle θ2 is 50°.

[0164] like Figure 8AAs shown, the phase characteristic B1 of the elastic wave device 1 in Embodiment 4 is improved compared with the phase characteristics B2 and B3 of the elastic wave devices in Comparative Examples 1 and 2 in frequency bands other than the main mode frequency band.

[0165] Especially Figure 8B As shown, at a frequency lower than the main mode's frequency band, the elastic wave device 1 of Embodiment 4, compared to the elastic wave devices of Comparative Examples 1 and 2, can reduce Rayleigh mode spurious signals. On the other hand, as... Figure 8C As shown, in the elastic wave device 1 of Embodiment 4, the main mode characteristics are obtained to the same extent as those of the elastic wave devices of Comparative Examples 1 and 2.

[0166] It should be noted that, to obtain Figures 8A to 8C The conditions for the elastic wave device 1 with phase characteristic B1 are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the first piezoelectric layer 3A is 0.05λ, the thickness of the second piezoelectric layer 3B is 0.15λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon. In the elastic wave device of Comparative Example 1, the thickness of the IDT electrode is 0.05λ, the thickness of the first piezoelectric layer is 0.2λ, the thickness of the low-velocity film is 0.15λ, and the thickness of the high-velocity film is 0.15λ. The material of the IDT electrode is aluminum, the material of the low-velocity film is silicon oxide, the material of the high-velocity film is silicon nitride, and the material of the support substrate is silicon. In the elastic wave device of Comparative Example 2, the thickness of the IDT electrode is 0.05λ, the thickness of the second piezoelectric layer is 0.2λ, the thickness of the low-velocity film is 0.15λ, and the thickness of the high-velocity film is 0.15λ. The material of the IDT electrode is aluminum, the material of the low-velocity film is silicon oxide, the material of the high-velocity film is silicon nitride, and the material of the support substrate is silicon.

[0167] (3) Effect

[0168] In the elastic wave device 1 of Embodiment 4, a first piezoelectric layer 3A (lithium tantalate piezoelectric layer) is stacked on the support substrate 2 side, and a second piezoelectric layer 3B (lithium niobate piezoelectric layer) is stacked on the IDT electrode 6 side. Therefore, compared to the case with only the first or second piezoelectric layer, it is easier to increase the fractional bandwidth.

[0169] (Implementation Method 5)

[0170] The electromechanical coupling coefficient of the elastic wave device 1 in Embodiment 5 is 4.0% or higher when the first piezoelectric layer 3A is on the side of the support substrate 2 and the second piezoelectric layer 3B is on the side of the IDT electrode 6, which differs from the elastic wave device 1 in Embodiment 4. It should be noted that, regarding the elastic wave device 1 in Embodiment 5, the same reference numerals are used for the same constituent elements as in the elastic wave device 1 in Embodiment 4, and descriptions are omitted.

[0171] (1) Structure

[0172] In the elastic wave device 1 of embodiment 5, the Euler angles of the first piezoelectric layer 3A and the second piezoelectric layer 3B are set such that the electromechanical coupling coefficient is 4.0% or more. When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is 0° or more and less than 180°, the electromechanical coupling coefficient is expressed by the following equation (3). When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is -180° or more and less than 0°, the electromechanical coupling coefficient is expressed by the following equation (4). Equations (3) and (4) represent formulas that make the electromechanical coupling coefficient 100 times. The second Euler angle θ1 satisfies θ1=θ1+180°×n (n=0, ±1, ±2). It should be noted that, regarding the first piezoelectric layer 3A and the second piezoelectric layer 3B in Embodiment 5, the description of the same structure and function as that in Embodiment 4 is omitted.

[0173] [Formula 5]

[0174]

[0175] [Formula 6]

[0176]

[0177] (2) Characteristics of elastic wave devices

[0178] Figures 9A to 9C The characteristics of the electromechanical coupling coefficient are shown when the ratio (T2 / T1) of the thickness T2 of the second piezoelectric layer 3B to the thickness T1 of the first piezoelectric layer 3A is changed. Figures 9A to 9C In each diagram, the "Euler angles of the first layer" is the second Euler angle θ1 in the Euler angles (0, θ1, 0) of the first piezoelectric layer 3A, and the "Euler angles of the second layer" is the second Euler angle θ2 in the Euler angles (0, θ2, 0) of the second piezoelectric layer 3B. This yields... Figures 9A to 9CThe conditions for the elastic wave device 1 with electromechanical coupling coefficient characteristics are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon.

[0179] Figure 9A The characteristics of the electromechanical coupling coefficient are shown when the ratio (T2 / T1) is 0.33. For example, the thickness T1 of the first piezoelectric layer 3A is 0.15λ, and the thickness T2 of the second piezoelectric layer 3B is 0.05λ. By selecting a combination of the second Euler angles θ1 and θ2 such that the electromechanical coupling coefficient is greater than 4.0%, good characteristics can be obtained.

[0180] Figure 9B The characteristics of the electromechanical coupling coefficient are shown when the ratio (T2 / T1) is 1. For example, the thickness T1 of the first piezoelectric layer 3A and the thickness T2 of the second piezoelectric layer 3B are both 0.10λ. Similar to the case where the ratio (T2 / T1) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the electromechanical coupling coefficient is 4.0% or higher.

[0181] Figure 9C The characteristics of the electromechanical coupling coefficient are shown when the ratio (T2 / T1) is 3. For example, the thickness T1 of the first piezoelectric layer 3A is 0.05λ, and the thickness T2 of the second piezoelectric layer 3B is 0.15λ. Similar to the case where the ratio (T2 / T1) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the electromechanical coupling coefficient is 4.0% or higher.

[0182] (3) Effect

[0183] In the elastic wave device 1 of embodiment 5, the electromechanical coupling coefficient is 4.0% or higher. This allows for efficient excitation of the main mode, which is dominated by SH waves, resulting in excellent characteristics. It should be noted that, as described above, equations (3) and (4) represent formulas for calculating the electromechanical coupling coefficient as a percentage. Therefore, the second Euler angle θ1 and the second Euler angle θ2 are values ​​where the electromechanical coupling coefficient expressed by equations (3) and (4) is 4.0% or higher.

[0184] (Implementation Method 6)

[0185] In Embodiment 6, the absolute value of the TCF in the elastic wave device 1, when the first piezoelectric layer 3A is on the support substrate 2 side and the second piezoelectric layer 3B is on the IDT electrode 6 side, differs from that in Embodiment 4. It should be noted that, regarding the elastic wave device 1 of Embodiment 6, the same reference numerals are used for the same constituent elements as in Embodiment 4, and descriptions are omitted.

[0186] (1) Structure

[0187] In Embodiment 6, the elastic wave device 1 sets the Euler angles of the first piezoelectric layer 3A and the second piezoelectric layer 3B such that the absolute value of the TCF is 20 ppm / ℃ or less. When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is 0° or more and less than 180°, the TCF is expressed by the following equation (7). When the second Euler angle θ1 of the first piezoelectric layer 3A is 0° or more and 180° or less, and the second Euler angle θ2 of the second piezoelectric layer 3B is -180° or more and less than 0°, the TCF is expressed by the following equation (8). It should be noted that, regarding the first piezoelectric layer 3A and the second piezoelectric layer 3B of Embodiment 6, descriptions of the same structure and function as those of the first piezoelectric layer 3A and the second piezoelectric layer 3B in Embodiment 4 are omitted.

[0188] [Formula 7]

[0189]

[0190] [Formula 8]

[0191]

[0192] (2) Characteristics of elastic wave devices

[0193] Figures 10A to 10C The characteristics of the TCF are shown when the ratio (T2 / T1) of the thickness T2 of the second piezoelectric layer 3B to the thickness T1 of the first piezoelectric layer 3A is changed. Figures 10A to 10C In each diagram, the "Euler angles of the first layer" is the second Euler angle θ1 in the Euler angles (0, θ1, 0) of the first piezoelectric layer 3A, and the "Euler angles of the second layer" is the second Euler angle θ2 in the Euler angles (0, θ2, 0) of the second piezoelectric layer 3B. This yields... Figures 10A to 10C The conditions for the elastic wave device 1 with TCF characteristics are as follows. The thickness of the IDT electrode 6 is 0.05λ, the thickness of the low-velocity film 4 is 0.15λ, and the thickness of the high-velocity film 5 is 0.15λ. The material of the IDT electrode 6 is aluminum, the material of the low-velocity film 4 is silicon oxide, the material of the high-velocity film 5 is silicon nitride, and the material of the support substrate 2 is silicon.

[0194] Figure 10A The characteristics of the TCF are shown when the ratio (T2 / T1) is 0.33. For example, the thickness T1 of the first piezoelectric layer 3A is 0.15λ, and the thickness T2 of the second piezoelectric layer 3B is 0.05λ. By selecting a combination of the second Euler angles θ1 and θ2 such that the TCF falls within the range of -20 ppm / ℃ to 20 ppm / ℃, good characteristics can be obtained. More preferably, a combination of the second Euler angles θ1 and θ2 is selected such that the TCF falls within the range of -10 ppm / ℃ to 10 ppm / ℃. This results in even better characteristics.

[0195] Figure 10B The characteristics of the TCF are shown when the ratio (T2 / T1) is 1. For example, the thickness T1 of the first piezoelectric layer 3A and the thickness T2 of the second piezoelectric layer 3B are both 0.10λ. Similar to the case where the ratio (T2 / T1) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the TCF is in the range of -20 ppm / ℃ or higher and 20 ppm / ℃ or lower. More preferably, a combination of the second Euler angles θ1 and θ2 is selected such that the TCF is in the range of -10 ppm / ℃ or higher and 10 ppm / ℃ or lower. This results in even better characteristics.

[0196] Figure 10C The characteristics of the TCF are shown when the ratio (T2 / T1) is 3. For example, the thickness T1 of the first piezoelectric layer 3A is 0.05λ, and the thickness T2 of the second piezoelectric layer 3B is 0.15λ. Similar to the case where the ratio (T2 / T1) is 0.33, good characteristics can be obtained by selecting a combination of the second Euler angles θ1 and θ2 such that the TCF falls within the range of -20 ppm / ℃ to 20 ppm / ℃. More preferably, a combination of the second Euler angles θ1 and θ2 is selected such that the TCF falls within the range of -10 ppm / ℃ to 10 ppm / ℃. This results in even better characteristics.

[0197] (3) Effect

[0198] In the elastic wave device 1 of Embodiment 6, the absolute value of TCF is in the range of 20 ppm / ℃ or less. Therefore, a good TCF can be achieved.

[0199] In the elastic wave device 1 of Embodiment 6, the absolute value of TCF is in the range of 10 ppm / ℃ or less. Therefore, a better TCF can be achieved.

[0200] (Implementation Method 7)

[0201] like Figure 11As shown, the elastic wave device 1b of Embodiment 7 is directly disposed on the second piezoelectric layer 3B on the support substrate 2, which is different from the elastic wave device 1 of Embodiment 1 (see Figure 1). Figure 2 (Different.) It should be noted that, regarding the elastic wave device 1b of Embodiment 7, the same markings are used for the same constituent elements as those of the elastic wave device 1 of Embodiment 1, and the descriptions are omitted.

[0202] (1) Structure

[0203] In the elastic wave device 1b of embodiment 7, as Figure 11 As shown, the second piezoelectric layer 3B is directly disposed on the support substrate 2. That is, the elastic wave device 1b does not have a low-velocity film 4 and a high-velocity film 5. On the other hand, the elastic wave device 1b, like the elastic wave device 1 of Embodiment 1, includes a support substrate 2, a first piezoelectric layer 3A and a second piezoelectric layer 3B, and an IDT electrode 6.

[0204] (2) Characteristics of elastic wave devices

[0205] In the elastic wave device 1b of Embodiment 7, similarly to the elastic wave device 1 of Embodiment 1, when the total film thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 0.66λ or less, the phase characteristics of the higher-order modes become smaller.

[0206] (3) Effect

[0207] In the elastic wave device 1b of Embodiment 7, similarly to the elastic wave device 1 of Embodiment 1, an elastic wave device is provided that can reduce Rayleigh mode spurious signals generated in a frequency band lower than the excitation mode used to obtain the characteristics, and higher-order mode spurious signals generated in a frequency band higher than the excitation mode. Furthermore, when the elastic wave device 1b is used as a filter, it can reduce Rayleigh mode spurious signals generated in the low-frequency band of the filter's passband, and higher-order mode spurious signals generated in the high-frequency band of the filter's passband.

[0208] (Implementation Method 8)

[0209] like Figure 12 As shown, the elastic wave device 1a of Embodiment 8 differs from the elastic wave device 1 of Embodiment 1 (see reference 1) in that it does not have a high-speed sound diaphragm 5. Figure 2 (Different.) It should be noted that, regarding the elastic wave device 1a of Embodiment 8, the same markings are used for the same constituent elements as those of the elastic wave device 1 of Embodiment 1, and the descriptions are omitted.

[0210] (1) Structure

[0211] In the elastic wave device 1a of embodiment 8, such as Figure 12As shown, the high-velocity sound membrane 5 is not present. That is, the low-velocity sound membrane 4 is directly disposed on the support substrate 2. On the other hand, the elastic wave device 1a, like the elastic wave device 1 of Embodiment 1, includes the support substrate 2, the first piezoelectric layer 3A and the second piezoelectric layer 3B, the low-velocity sound membrane 4, and the IDT electrode 6.

[0212] In the elastic wave device 1a of embodiment 8, the support substrate 2 is a high-velocity acoustic support substrate. The high-velocity acoustic support substrate is a support substrate in which the velocity of the bulk wave propagating on the high-velocity acoustic support substrate is higher than the velocity of the elastic wave propagating on the first piezoelectric layer 3A and the second piezoelectric layer 3B. Therefore, the Q value of the elastic wave device 1a can be further improved.

[0213] (2) Characteristics of elastic wave devices

[0214] In the elastic wave device 1a of embodiment 8, similarly to the elastic wave device 1 of embodiment 1, when the total film thickness of the first piezoelectric layer 3A and the second piezoelectric layer 3B is 0.66λ or less, the phase characteristics of the higher-order modes become smaller.

[0215] (3) Effect

[0216] In the elastic wave device 1a of embodiment 8, similarly to the elastic wave device 1 of embodiment 1, a low-velocity film 4 is provided between the support substrate 2 and the second piezoelectric layer 3B in the thickness direction (first direction D1) of the support substrate 2. This improves the Q value of the elastic wave device 1a.

[0217] In the elastic wave device 1a of embodiment 8, the support substrate 2 is a high-velocity acoustic support substrate. This allows for a further improvement in the Q value of the elastic wave device 1a.

[0218] The embodiments and modifications described above are only a part of the various embodiments and modifications of the present invention. Furthermore, the embodiments and modifications can be modified in various ways, depending on the design, etc., as long as they achieve the objectives of the present invention.

[0219] For example, the surface of the second piezoelectric layer 3B in the first piezoelectric layer 3A and the surface of the first piezoelectric layer 3A in the second piezoelectric layer 3B can also be surfaces of the same polarity. Specifically, it is also possible that in the first piezoelectric layer 3A, if the surface on the side of the IDT electrode 6 is the front side and the surface on the side of the support substrate 2 is the back side, then in the second piezoelectric layer 3B, the surface on the side of the IDT electrode 6 is the back side and the surface on the side of the support substrate 2 is the front side. Alternatively, it is also possible that in the first piezoelectric layer 3A, if the surface on the side of the IDT electrode 6 is the back side and the surface on the side of the support substrate 2 is the front side, then in the second piezoelectric layer 3B, the surface on the side of the IDT electrode 6 is the front side and the surface on the side of the support substrate 2 is the back side. In this case, when the elastic wave device 1 is used as a filter, it is also possible to reduce Rayleigh mode spurious emissions generated in the low-frequency band of the filter's passband and higher-order mode spurious emissions generated in the high-frequency band of the filter's passband.

[0220] (Way)

[0221] The following methods are disclosed in this specification.

[0222] The elastic wave device (1; 1a; 1b; 1c) of the first embodiment includes a support substrate (2), a laminate (3), and an IDT electrode (6). The laminate (3) includes a stacked lithium tantalate piezoelectric layer (first piezoelectric layer 3A) and a lithium niobate piezoelectric layer (second piezoelectric layer 3B), and is disposed on the support substrate (2). The IDT electrode (6) is disposed on the laminate (3) and has a plurality of electrode fingers (63). When the wavelength of the elastic wave, determined by the spacing (P1) of the plurality of electrode fingers (63), is set as λ, the thickness of the laminate (3) is 0.66λ or less.

[0223] According to the elastic wave device (1; 1a; 1b; 1c) of the first embodiment, Rayleigh mode spurious signals generated in the frequency band lower than the excitation mode used to obtain the characteristics, and higher-order mode spurious signals generated in the frequency band higher than the excitation mode, can be reduced. Furthermore, when the elastic wave device (1; 1a; 1b; 1c) is used as a filter, Rayleigh mode spurious signals generated in the low-frequency band of the filter's passband, and higher-order mode spurious signals generated in the high-frequency band of the filter's passband, can be reduced.

[0224] The second type of elastic wave device (1; 1a; 1b; 1c) is based on the first type, with a lithium tantalate piezoelectric layer (first piezoelectric layer 3A) stacked on the side of the IDT electrode (6). A lithium niobate piezoelectric layer (second piezoelectric layer 3B) is stacked on the side of the support substrate (2).

[0225] According to the elastic wave device of the second method (1; 1a; 1b; 1c), the temperature characteristics can be improved.

[0226] The third type of elastic wave device (1; 1a; 1b; 1c) is based on the first type, with a lithium tantalate piezoelectric layer (first piezoelectric layer 3A) stacked on the support substrate (2) side. A lithium niobate piezoelectric layer (second piezoelectric layer 3B) is stacked on the IDT electrode (6) side.

[0227] According to the third-party elastic wave device (1; 1a; 1b; 1c), compared with the case of only lithium tantalate piezoelectric layer or lithium niobate piezoelectric layer, it is easy to increase the fractional bandwidth.

[0228] The fourth type of elastic wave device (1; 1a; 1b; 1c) is based on the second type, with the thickness of the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) set to T1, the thickness of the lithium niobate piezoelectric layer (second piezoelectric layer 3B) set to T2, the second Euler angle of the lithium tantalate piezoelectric layer set to θ1, and the second Euler angle of the lithium niobate piezoelectric layer set to θ2. When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is 0° or more and less than 180°, the electromechanical coupling coefficient satisfies equation (1). When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is -180° or more and less than 0°, the electromechanical coupling coefficient satisfies equation (2). The second Euler angles θ1 and θ2 are values ​​where the electromechanical coupling coefficient is 4.0% or more. Equations (1) and (2) represent formulas for calculating the electromechanical coupling coefficient as a percentage. Therefore, the second Euler angle θ1 and the second Euler angle θ2 are expressed by equations (1) and (2) as electromechanical coupling coefficients of 4.0% or higher. It should be noted that the second Euler angle θ1 satisfies θ1=θ1+180°×n (n=0、±1、±2).

[0229] [Formula 9]

[0230]

[0231] [Formula 10]

[0232]

[0233] According to the elastic wave device of the fourth method (1; 1a; 1b; 1c), the main mode with SH wave as the main component can be efficiently excited, and thus good characteristics can be obtained.

[0234] The fifth type of elastic wave device (1; 1a; 1b; 1c) is based on the third type, with the thickness of the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) set to T1, the thickness of the lithium niobate piezoelectric layer (second piezoelectric layer 3B) set to T2, the second Euler angle of the lithium tantalate piezoelectric layer set to θ1, and the second Euler angle of the lithium niobate piezoelectric layer set to θ2. When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is 0° or more and less than 180°, the electromechanical coupling coefficient satisfies equation (3). When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is -180° or more and less than 0°, the electromechanical coupling coefficient satisfies equation (4). The second Euler angles θ1 and θ2 are values ​​where the electromechanical coupling coefficient is 4.0% or more. Equations (3) and (4) represent formulas for calculating the electromechanical coupling coefficient as a percentage. Therefore, the second Euler angle θ1 and the second Euler angle θ2 are electromechanical coupling coefficients expressed by equations (3) and (4) that are values ​​of 4.0% or higher. It should be noted that the second Euler angle θ1 satisfies θ1=θ1+180°×n (n=0、±1、±2).

[0235] [Formula 11]

[0236]

[0237] [Formula 12]

[0238]

[0239] According to the elastic wave device of the fifth method (1; 1a; 1b; 1c), the main mode with SH wave as the main component can be efficiently excited, and therefore, good characteristics can be obtained.

[0240] The sixth type of elastic wave device (1; 1a; 1b; 1c) is based on the second type, with the thickness of the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) set to T1, the thickness of the LiNbO3 piezoelectric layer (second piezoelectric layer 3B) set to T2, the second Euler angle of the lithium tantalate piezoelectric layer set to θ1, and the second Euler angle of the lithium niobate piezoelectric layer set to θ2. When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is 0° or more and less than 180°, the TCF satisfies equation (5). When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is -180° or more and less than 0°, the TCF satisfies equation (6). The second Euler angles θ1 and θ2 are values ​​in the range where the absolute value of the TCF is 20 ppm / ℃ or less.

[0241] [Formula 13]

[0242]

[0243] [Formula 14]

[0244]

[0245] According to the elastic wave device of the sixth method (1; 1a; 1b; 1c), a good TCF can be achieved.

[0246] The elastic wave device of the seventh type (1; 1a; 1b; 1c) is based on the sixth type, wherein the second Euler angle θ1 and the second Euler angle θ2 are values ​​in the range where the absolute value of TCF is below 10 ppm / ℃.

[0247] According to the elastic wave device of the seventh method (1; 1a; 1b; 1c), a better TCF can be achieved.

[0248] The eighth type of elastic wave device (1; 1a; 1b; 1c) is based on the third type, with the thickness of the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) set to T1, the thickness of the lithium niobate piezoelectric layer (second piezoelectric layer 3B) set to T2, the second Euler angle of the lithium tantalate piezoelectric layer set to θ1, and the second Euler angle of the lithium niobate piezoelectric layer set to θ2. When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is 0° or more and less than 180°, the TCF satisfies equation (7). When the second Euler angle θ1 is 0° or more and 180° or less, and the second Euler angle θ2 is -180° or more and less than 0°, the TCF satisfies equation (8). The second Euler angles θ1 and θ2 are values ​​in the range where the absolute value of the TCF is 20 ppm / ℃ or less.

[0249] [Formula 15]

[0250]

[0251] [Formula 16]

[0252]

[0253] According to the elastic wave device of the eighth method (1; 1a; 1b; 1c), a good TCF can be achieved.

[0254] The elastic wave device of the ninth type (1; 1a; 1b; 1c) is based on the eighth type, wherein the second Euler angle θ1 and the second Euler angle θ2 are values ​​in the range where the absolute value of TCF is below 10 ppm / ℃.

[0255] According to the elastic wave device of the ninth method (1; 1a; 1b; 1c), a better TCF can be achieved.

[0256] The elastic wave device of the tenth type (1; 1a; 1b; 1c) is based on any of the first to ninth types, wherein the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) is a single crystal structure, and the lithium niobate piezoelectric layer (second piezoelectric layer 3B) is a single crystal structure.

[0257] The elastic wave device of the eleventh method (1; 1a; 1b; 1c) is based on any one of the first to tenth methods, wherein at least one of the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) and the lithium niobate piezoelectric layer (second piezoelectric layer 3B) is rotated Y-cut.

[0258] According to the elastic wave device of the eleventh method (1; 1a; 1b; 1c), SH waves can be excited more efficiently and are easy to use.

[0259] The elastic wave device of the twelfth type (1; 1a; 1b; 1c) is based on the eleventh type, wherein both sides of the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) and the lithium niobate piezoelectric layer (second piezoelectric layer 3B) are rotated Y-cut.

[0260] According to the elastic wave device of the twelfth method (1; 1a; 1b; 1c), SH waves can be excited more efficiently.

[0261] The elastic wave device of the thirteenth type (1; 1a; 1c) further includes a low-velocity sound membrane (4) in addition to any of the first to twelfth types. In the low-velocity sound membrane (4), the sound velocity of the bulk wave propagating in the low-velocity sound membrane (4) is lower than the sound velocity of the bulk wave propagating in the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) and the lithium niobate piezoelectric layer (second piezoelectric layer 3B). The low-velocity sound membrane (4) is disposed between the support substrate (2) and the laminate (3).

[0262] According to the elastic wave device (1; 1a; 1c) of the thirteenth method, the Q value of the elastic wave device (1; 1a; 1c) can be improved.

[0263] The elastic wave device of the fourteenth type (1; 1c) further includes a high-velocity acoustic membrane (5) in addition to the features of the thirteenth type. In the high-velocity acoustic membrane (5), the velocity of the bulk wave propagating in the high-velocity acoustic membrane (5) is higher than the velocity of the elastic wave propagating in the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) and the lithium niobate piezoelectric layer (second piezoelectric layer 3B). The high-velocity acoustic membrane (5) is disposed between the support substrate (2) and the low-velocity acoustic membrane (4).

[0264] According to the elastic wave device (1; 1c) of the fourteenth method, the Q value of the elastic wave device (1) can be further improved.

[0265] The elastic wave device (1c) of the fifteenth embodiment, based on any one of the first to fourteenth embodiments, further includes a silicon oxide layer (3C) in the laminate (3). The silicon oxide layer (3C) is disposed between the lithium tantalate piezoelectric layer (first piezoelectric layer 3A) and the lithium niobate piezoelectric layer (second piezoelectric layer 3B).

[0266] Explanation of reference numerals in the attached figures

[0267] 1, 1a, 1b, 1c Elastic wave devices;

[0268] 2 supporting base plate;

[0269] 21 First main face;

[0270] 22 Second Main Face;

[0271] 3. Layered structure;

[0272] 3A First piezoelectric layer (lithium tantalate piezoelectric layer);

[0273] 3B Second piezoelectric layer (lithium niobate piezoelectric layer);

[0274] 3C silicon oxide layer;

[0275] 31 First main face;

[0276] 32 Second main face;

[0277] 4. Low-velocity membrane;

[0278] 5. High-speed acoustic membrane;

[0279] 6 IDT electrodes;

[0280] 61 electrodes;

[0281] 61A First electrode;

[0282] 61B Second Electrode;

[0283] 62. Busbars;

[0284] 62A First Busbar;

[0285] 62B Second Busbar;

[0286] 63. Electrode finger;

[0287] 63A First electrode indicator;

[0288] 63B Second Electrode Indication;

[0289] 7. Reflector;

[0290] 8. Wiring Department;

[0291] 81 First Wiring Department;

[0292] 82 Second Wiring Section;

[0293] T1 thickness;

[0294] T2 thickness;

[0295] θ1 Second Euler angle;

[0296] θ2 Second Euler angle;

[0297] P1 Electrode finger spacing;

[0298] S1 distance;

[0299] W1 is the cross width;

[0300] λ Wavelength;

[0301] Phase characteristics of A1, A2, and A3;

[0302] Phase characteristics of B1, B2, and B3;

[0303] D1 First direction;

[0304] D2 Second direction;

[0305] D3 third direction.

Claims

1. An elastic wave device, comprising: support base plate; A laminate comprising a stacked lithium tantalate piezoelectric layer and a lithium niobate piezoelectric layer, and disposed on the supporting substrate; and An IDT electrode, disposed in the laminate, has multiple electrode fingers. When the wavelength of the elastic wave, which is determined by the spacing of the plurality of electrode fingers, is set to λ, the thickness of the laminate is 0.66λ or less.

2. The elastic wave device according to claim 1, wherein, The lithium tantalate piezoelectric layer is stacked on the IDT electrode side. The lithium niobate piezoelectric layer is stacked on the side of the support substrate.

3. The elastic wave device according to claim 1, wherein, The lithium tantalate piezoelectric layer is stacked on the support substrate side. The lithium niobate piezoelectric layer is stacked on the side of the IDT electrode.

4. The elastic wave device according to claim 2, wherein, When the thickness of the lithium tantalate piezoelectric layer is set to T1, the thickness of the lithium niobate piezoelectric layer is set to T2, the second Euler angle of the lithium tantalate piezoelectric layer is set to θ1, and the second Euler angle of the lithium niobate piezoelectric layer is set to θ2, When the second Euler angle θ1 is greater than or equal to 0° and less than or equal to 180°, and the second Euler angle θ2 is greater than or equal to 0° and less than or equal to 180°, the electromechanical coupling coefficient satisfies equation (1). When the second Euler angle θ1 is greater than 0° and less than 180°, and the second Euler angle θ2 is greater than -180° and less than 0°, the electromechanical coupling coefficient satisfies equation (2). The second Euler angles θ1 and θ2 are values ​​where the electromechanical coupling coefficient is 4.0% or higher. [Formula 1] [Formula 2] 5. The elastic wave device according to claim 3, wherein, When the thickness of the lithium niobate piezoelectric layer is set to T1, the thickness of the lithium tantalate piezoelectric layer is set to T2, the second Euler angle of the lithium niobate piezoelectric layer is set to θ1, and the second Euler angle of the lithium tantalate piezoelectric layer is set to θ2,... When the second Euler angle θ1 is greater than or equal to 0° and less than or equal to 180°, and the second Euler angle θ2 is greater than or equal to 0° and less than or equal to 180°, the electromechanical coupling coefficient satisfies equation (3). When the second Euler angle θ1 is greater than 0° and less than 180°, and the second Euler angle θ2 is greater than -180° and less than 0°, the electromechanical coupling coefficient satisfies equation (4). The second Euler angles θ1 and θ2 are values ​​where the electromechanical coupling coefficient is 4.0% or higher. [Formula 3] [Formula 4] 6. The elastic wave device according to claim 2, wherein, When the thickness of the lithium tantalate piezoelectric layer is set to T1, the thickness of the lithium niobate piezoelectric layer is set to T2, the second Euler angle of the lithium tantalate piezoelectric layer is set to θ1, and the second Euler angle of the lithium niobate piezoelectric layer is set to θ2, When the second Euler angle θ1 is greater than or equal to 0° and less than or equal to 180°, and the second Euler angle θ2 is greater than or equal to 0° and less than or equal to 180°, the TCF satisfies equation (5). When the second Euler angle θ1 is greater than or equal to 0° and less than or equal to 180°, and the second Euler angle θ2 is greater than or equal to -180° and less than or equal to 0°, the TCF satisfies equation (6). The second Euler angle θ1 and the second Euler angle θ2 are values ​​in the range where the absolute value of the TCF is below 20 ppm / ℃. [Formula 5] [Formula 6] 7. The elastic wave device according to claim 6, wherein, The second Euler angle θ1 and the second Euler angle θ2 are values ​​in the range where the absolute value of the TCF is below 10 ppm / ℃.

8. The elastic wave device according to claim 3, wherein, When the thickness of the lithium niobate piezoelectric layer is set to T1, the thickness of the lithium tantalate piezoelectric layer is set to T2, the second Euler angle of the lithium niobate piezoelectric layer is set to θ1, and the second Euler angle of the lithium tantalate piezoelectric layer is set to θ2,... When the second Euler angle θ1 is greater than or equal to 0° and less than or equal to 180°, and the second Euler angle θ2 is greater than or equal to 0° and less than or equal to 180°, the TCF satisfies equation (7). When the second Euler angle θ1 is greater than or equal to 0° and less than or equal to 180°, and the second Euler angle θ2 is greater than or equal to -180° and less than or equal to 0°, the TCF satisfies equation (8). The second Euler angle θ1 and the second Euler angle θ2 are values ​​in the range where the absolute value of the TCF is below 20 ppm / ℃. [Formula 7] [Formula 8] 9. The elastic wave device according to claim 8, wherein, The second Euler angle θ1 and the second Euler angle θ2 are values ​​in the range where the absolute value of the TCF is below 10 ppm / ℃.

10. The elastic wave device according to any one of claims 1 to 9, wherein, The lithium tantalate piezoelectric layer has a single-crystal structure. The lithium niobate piezoelectric layer has a single-crystal structure.

11. The elastic wave device according to any one of claims 1 to 10, wherein, At least one of the lithium tantalate piezoelectric layer and the lithium niobate piezoelectric layer is rotary Y-cut.

12. The elastic wave device according to claim 11, wherein, Both the lithium tantalate piezoelectric layer and the lithium niobate piezoelectric layer are rotary Y-cut.

13. The elastic wave device according to any one of claims 1 to 12, wherein, The elastic wave device further includes a low-velocity diaphragm, wherein the velocity of sound of the bulk wave propagating on the low-velocity diaphragm is lower than the velocity of sound of the bulk wave propagating on the lithium tantalate piezoelectric layer and the lithium niobate piezoelectric layer. The low-velocity membrane is disposed between the support substrate and the laminate.

14. The elastic wave device according to claim 13, wherein, The elastic wave device also includes a high-velocity acoustic membrane, wherein the sound speed of the bulk wave propagating on the high-velocity acoustic membrane is higher than the sound speed of the elastic wave propagating on the lithium tantalate piezoelectric layer and the lithium niobate piezoelectric layer. The high-velocity membrane is disposed between the support substrate and the low-velocity membrane.

15. The elastic wave device according to any one of claims 1 to 14, wherein, The laminate further includes a silicon oxide layer disposed between the lithium tantalate piezoelectric layer and the lithium niobate piezoelectric layer.

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