Elastic wave device

Abstract

To provide an elastic wave device which suppresses spurious.SOLUTION: An elastic wave device includes: a support substrate 1 having a plurality of protrusions; an intermediate layer 5 disposed on the support substrate; a piezoelectric layer 2 disposed on the intermediate layer on a side opposite to the support substrate; and an electrode layer 4 disposed on the piezoelectric layer, where the plurality of protrusions include a plurality of first protrusions 21 and a plurality of second protrusions 22 having a height lower than that of the first protrusions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an acoustic wave device using a surface acoustic wave. [Background technology]

[0002] For example, an acoustic wave device using surface acoustic waves is known, which is used in a transmission filter and a reception filter of a duplexer.

[0003] For example, Patent Document 1 discloses an acoustic wave device in which an intermediate layer containing silica is provided between a piezoelectric layer (piezoelectric substrate) and a support substrate, the upper surface of the support substrate and the lower surface of the piezoelectric layer are roughened, and the interface between the intermediate layer and the piezoelectric layer and the interface between the intermediate layer and the support substrate are uneven. Patent Document 2 discloses an acoustic wave device in which an intermediate layer is provided between the piezoelectric layer and the support substrate, and protrusions that reach the intermediate layer are arranged on the upper surface of the support substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-61258 [Patent Document 2] Special Publication No. 2023-527784 Summary of the Invention [Problem to be solved by the invention]

[0005] In the acoustic wave device of Patent Document 1, the top surface of the support substrate is roughened by wet etching, so the unevenness of the top surface is random (irregular), and there is a risk that the uniformity of the magnitude of the spurious signals will be lost depending on the location of the rough surface. In the acoustic wave device of Patent Document 2, if the height of the protrusions that make up the unevenness of the support substrate is uniform, the randomness described in the acoustic wave device of Patent Document 1 above will disappear, the problem of uniformity in the magnitude of spurious signals will be resolved, and the spurious signals can be reduced. However, an acoustic wave device that can suppress spurious signals by scattering bulk waves more is desired. In view of these problems, an object of the present invention is to provide an acoustic wave device capable of scattering spurious signals. [Means for solving the problem]

[0006] One aspect of the acoustic wave device of the present invention is a support substrate having a plurality of protrusions; an intermediate layer disposed on the support substrate so as to fill recesses formed between the protrusions; a piezoelectric layer disposed on the intermediate layer opposite the support substrate; an electrode layer disposed on the piezoelectric layer opposite the intermediate layer; Equipped with The plurality of protrusions includes a plurality of first protrusions and a plurality of second protrusions that are lower in height than the first protrusions. Acoustic wave devices.

[0007] In a specific aspect of the acoustic wave device of the present invention, the plurality of first protrusions and the plurality of second protrusions are arranged in a repeated and regular pattern in a cross section taken along a line connecting central portions of adjacent first protrusions in a plan view, with the distance between the central portions of adjacent first protrusions being one period. It is something.

[0008] As a specific embodiment of the above-mentioned aspect of the acoustic wave device of the present invention, the plurality of first protrusion portions and the plurality of second protrusion portions are arranged alternately in a cross-sectional view when a straight line is taken as the cutting line.

[0009] As a specific embodiment of the above-described aspect, the acoustic wave device of the present invention includes: the intermediate layer includes a top layer in contact with the piezoelectric layer, a bottom layer in contact with the support substrate, and a middle layer interposed between the top layer and the bottom layer; The first protrusions penetrate the bottom layer, and the upper ends of the first protrusions are provided on the middle layer.

[0010] In a specific aspect of the acoustic wave device of the present invention, the intermediate layer includes a top layer in contact with the piezoelectric layer, a bottom layer in contact with the support substrate, and a middle layer interposed between the top layer and the bottom layer; The first protrusions penetrate the bottom layer and the middle layer, and upper ends of the first protrusions are located on the top layer. It is something.

[0011] In a specific aspect of the acoustic wave device of the present invention, the intermediate layer includes a top layer in contact with the piezoelectric layer, a bottom layer in contact with the support substrate, and a middle layer interposed between the top layer and the bottom layer; The upper ends of the plurality of second protrusions are located in the lowermost layer.

[0012] In a specific aspect of the acoustic wave device of the present invention, the first protrusion and the second protrusion have a conical shape or a polygonal shape.

[0013] In a specific aspect of the acoustic wave device of the present invention, the first protrusions and the second protrusions are striped in plan view. [Effects of the Invention]

[0014] As described above, the acoustic wave device of the present invention includes a plurality of first protrusions and a plurality of second protrusions that are lower in height than the first protrusions, and thus provides two types of protrusions with different heights, which makes it possible to scatter bulk waves to the intermediate layer more efficiently than an acoustic wave device in which the protrusions are all the same height. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view illustrating a first embodiment of an acoustic wave device according to the present invention. [Figure 2] 2 is a plan view of a support substrate in the acoustic wave device according to the first embodiment of the present invention. FIG. [Figure 3] 3(a) is a plan view of a support substrate in a second embodiment of an acoustic wave device according to the present invention, and FIG. 3(b) is a cross-sectional view of the acoustic wave device in the second embodiment. [Figure 4] Fig. 4(a) is a plan view of a support substrate in a third embodiment of an acoustic wave device according to the present invention, and Fig. 4(b) is a cross-sectional view of the acoustic wave device in the third embodiment. [Figure 5] Fig. 5(a) is a plan view of a support substrate in an acoustic wave device according to a fourth embodiment of the present invention, and Fig. 5(b) is a cross-sectional view of the acoustic wave device according to the fourth embodiment. [Figure 6] Fig. 6(a) is a plan view of a support substrate in an acoustic wave device according to a fifth embodiment of the present invention, and Fig. 6(b) is a cross-sectional view of the acoustic wave device according to the fifth embodiment. [Figure 7] Fig. 7(a) is a plan view of a support substrate in an acoustic wave device according to a sixth embodiment of the present invention, and Fig. 7(b) is a cross-sectional view of the acoustic wave device according to the sixth embodiment. [Figure 8] Fig. 8(a) is a plan view of a support substrate in an acoustic wave device according to a seventh embodiment of the present invention, and Fig. 8(b) is a cross-sectional view of the acoustic wave device according to the seventh embodiment. [Figure 9]9(a) is a plan view of a support substrate in an acoustic wave device according to an eighth embodiment of the present invention, and FIG. 9(b) is a cross-sectional view of the acoustic wave device according to the eighth embodiment. [Figure 10] Fig. 10(a) is a plan view of a support substrate in an acoustic wave device according to a ninth embodiment of the present invention, and Fig. 10(b) is a cross-sectional view of the acoustic wave device according to the ninth embodiment. [Figure 11] Fig. 11(a) is a plan view of a support substrate in a tenth embodiment of an acoustic wave device according to the present invention, and Fig. 11(b) is a cross-sectional view of the acoustic wave device in the tenth embodiment. [Figure 12] 11 is a cross-sectional view showing an example in which a first protrusion portion of a third embodiment of an acoustic wave device according to the present invention is modified. FIG. [Figure 13] 10 is a cross-sectional view illustrating an example in which the upper ends of the first protrusion and the second protrusion of the acoustic wave device according to a third embodiment of the present invention are modified. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Definitions in the explanation> In the embodiments described below, the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, and other factors may differ from the actual figures. Furthermore, the dimensional relationships and ratios may differ between the drawings. Regarding the X and Y directions, the X direction represents the arrangement direction of the electrode fingers, the Y direction represents the extension direction of the electrode fingers, and the Z direction represents the stacking direction of the support substrate and piezoelectric layer. However, in the plan view, the X and Y directions may form an arrangement pattern of the first and second protrusions at an angle to the arrangement direction and extension direction of the electrode fingers. Note that these X, Y, and Z directions do not necessarily coincide with the X-axis and Y-axis directions of the crystal orientation of the piezoelectric layer. Virtual lines are included in the drawings to illustrate the planar pattern of the substrate and do not actually exist on the substrate.

[0017] First Embodiment A first embodiment will be described as an embodiment of an acoustic wave device according to the present invention. Fig. 1 is a cross-sectional view of the acoustic wave device of the first embodiment. As shown in Fig. 1, the acoustic wave device 100 includes a support substrate 1, an intermediate layer 5, a piezoelectric layer 2, and an electrode layer 4. The acoustic wave device 100 is configured as a surface acoustic wave device that operates substantially with acoustic waves having a wavelength (λ) of, for example, 4.2 µm.

[0018] As shown in FIG. 1, the acoustic wave device 100 includes a piezoelectric layer 2. The piezoelectric layer 2 is a rotated Y-cut X-propagation single-crystal lithium tantalate (LiTaO3) layer, but a single-crystal lithium niobate (LiNbO3) layer may also be used. In this embodiment, the thickness of the piezoelectric layer 2 is ¼ (λ / 4) the wavelength of the acoustic wave, i.e., a thickness (T2) of approximately 1.68 μm. However, the thickness (T2) of the piezoelectric layer 2 may be changed to a value within the range of 0.1 μm to 30 μm.

[0019] In FIG. 1, an IDT (Interdigital Transistor) is formed on the upper surface of the piezoelectric layer 2. An electrode layer 4 is provided on the IDT electrode, forming a dielectric film (dielectric film) on the IDT electrode. In this embodiment, the thickness (width in the Z direction) of the electrode layer 4 is 300 nm, but may be changed in the range of 10 nm to 5000 nm. The pitch of the electrode fingers of the IDT electrode is 1 / 2 the wavelength λ. The shape and number of the electrode fingers of the IDT electrode formed by the electrode layer 4 are designed appropriately depending on the conditions, so a detailed description will be omitted.

[0020] 1, the intermediate layer 5 in this embodiment is a single layer. The material of the intermediate layer 5 is silicon dioxide in this embodiment, but it may also be silicon oxide fluoride, silicon nitride, or aluminum nitride. The intermediate layer 5 is formed on the support substrate 1 so as to fill the recess 6 formed between the inclined surfaces of the first protrusion 21 and the second protrusion 22, and to cover the first protrusion 21 and the second protrusion 22.

[0021] In this embodiment, the material of the support substrate 1 is sapphire (Al2O3). However, the support substrate 1 may also be a silicon carbide substrate, silicon substrate, spinel substrate, quartz substrate, crystal substrate, or alumina substrate. In this embodiment, the thickness of the support substrate 1 (the width from the bottom to the top surface 31 of the support substrate 1 in FIG. 1) is 200 μm, but the thickness may be in the range of 100 μm to 1 mm.

[0022] A first protrusion 21 and a second protrusion 22 are provided on an upper surface 31 of the support substrate 1, protruding from the upper surface 31 toward the piezoelectric layer 2. An upper end 21a as the center of the first protrusion 21 and an upper end 22a as the center of the second protrusion 22 are both located on the intermediate layer 5. An upper end 22a of the second protrusion 22 is located lower in the Z direction than an upper end 21a of the first protrusion 21. In other words, the second protrusion 22 is a protrusion that is lower than the first protrusion 21.

[0023] Fig. 2 is a plan view of the support substrate 1. When the straight virtual line 51 in Fig. 2 is set as the cutting line (AA cutting line), the first protrusions 21 and the second protrusions 22 are alternately arranged in cross section, as in the cross-sectional view of Fig. 1.

[0024] 2, first protrusions 21 and second protrusions 22 are provided on the upper surface 31 of the support substrate 1. The first protrusions 21 and second protrusions 22 are alternately arranged along a cutting line AA (imaginary line 51), which is a straight line parallel to the X direction. That is, the first protrusions 21 and second protrusions 22 are alternately and repeatedly arranged in the X direction, with the distance between the upper ends 21a of adjacent first protrusions 21 as the central portions being one period (for example, the period in the X direction is from imaginary line 41 to imaginary line 43). The first protrusions 21 and second protrusions 22 are also repeatedly arranged in the Y direction (the up-down direction in FIG. 2). The upper ends 21a of adjacent first protrusions 21 in the Y direction (from imaginary line 51 to imaginary line 52) constitute one period of the repeated arrangement in the Y direction.

[0025] Furthermore, the upper end 21a of the first protrusion 21, which is the center in a plan view, and the upper end 22a of the second protrusion 22, which is the center in a plan view, are aligned in a row along the imaginary lines 51, 52, and 53 in the X direction. Furthermore, in the Y direction, the upper end 21a of the first protrusion 21 and the upper end 22a of the second protrusion 22 are aligned parallel to and in parallel with the imaginary lines 41 and 42.

[0026] In the plan view of FIG. 2, the number of first protrusions 21 and second protrusions 22 and the number of periods at which they are arranged are not limited to those shown, and may be increased.

[0027] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0028] Second Embodiment A second embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 3(a) is a plan view of a support substrate 1B of the second embodiment, and Fig. 3(b) is a BB cross-sectional view of the acoustic wave device of the second embodiment. Parts with the same functions and names as those in the first embodiment described above are assigned the same reference numerals, and their description will be omitted.

[0029] 3(b), the intermediate layer 5 of the acoustic wave device 100B of the second embodiment is provided between the support substrate 1B and the piezoelectric layer 2. The intermediate layer 5 has a top layer 11 in contact with the piezoelectric layer 2, a bottom layer 13 in contact with the support substrate 1B, and a middle layer 12 formed between the top layer 11 and the bottom layer 13.

[0030] The materials of the top layer 11, middle layer 12, and bottom layer 13 of the intermediate layer 5 are each selected from silicon, silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide. In this embodiment, the top layer 11 and bottom layer 13 are made of silicon dioxide, and the middle layer 12 is made of silicon nitride.

[0031] The middle layer 12 has a higher acoustic propagation velocity than the top layer 11 and the bottom layer 13. By configuring the middle layer 5 in this way, the middle layer 12 has a three-layer structure and has a higher acoustic propagation velocity than the top layer 11 and the bottom layer 13, thereby enabling the bulk waves to be scattered favorably.

[0032] Regarding thickness, for example, in this embodiment, the thickness T4 of the top layer 11 is 600 nm (T4), the thickness T2 of the bottom layer 13 is 600 nm, and the thickness T3 of the middle layer 12 is 500 nm. Therefore, the total thickness of the intermediate layer 5 (T2+T3+T4) is 1700 nm (i.e., 1.7 μm). However, the thickness of the intermediate layer 5 may be changed within a range of 1.5 μm to 10 μm. The thickness of the intermediate layer 5 is similar in other embodiments described below.

[0033] The first protrusion 21 penetrates the bottom layer 13 and the middle layer 12, and the upper end 21a of the first protrusion 21 is provided on the top layer 11. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1B to the bottom layer 13. The second protrusion 22 is lower than the first protrusion 21. Alternatively, as shown in FIG. 12 , the upper end 21a of the first protrusion 21 may be provided on the middle layer 12, and the upper end 22a of the second protrusion 22 may be disposed on the bottom layer 13.

[0034] A bonding layer (not shown) may be provided between the piezoelectric layer 2 and the top layer 11. The bonding layer is made of silicon. The thickness of the bonding layer is preferably 20 nm or less, more preferably 2 to 9 nm, for example, 5 nm.

[0035] When the straight virtual line 51B is set as the cutting line (BB cutting line), the first protrusions 21 and the second protrusions 22 are arranged alternately and regularly in cross section, as shown in the cross section of Figure 3(b).

[0036] 3(a), the upper end 21a as the center of the first protrusion 21 and the upper end 22a as the center of the second protrusion 22 are aligned in a row along imaginary lines 51B, 52B, and 53B in the X direction. Furthermore, the upper end 22a as the center of the second protrusion 22 is aligned in a row along imaginary lines 54B and 53B in the X direction. Furthermore, in the Y direction, the upper ends 21a and 22a of the first protrusion 21 and the second protrusion 22 are aligned in a row, with their upper ends 21a and 22a parallel to imaginary lines 41B, 42B, and 43B. In addition, in the X direction, the distance between upper ends 21a as the centers of adjacent first protrusions 21 is one period (one period in the X direction is from virtual line 41B to virtual line 43B), and the first protrusions 21 and second protrusions 22 (for example, the first protrusions 21 and second protrusions 22 on virtual line 51B) are repeatedly arranged. In addition, in the Y direction, the distance between upper ends 21a as the centers of adjacent first protrusions 21 is one period (one period in the Y direction is from virtual line 51B to virtual line 52B), and the first protrusions 21 (for example, the first protrusions 21 on virtual line 41B and virtual line 43B) and second protrusions 22 (for example, the second protrusion 22 on virtual line 42B) are repeatedly arranged.

[0037] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0038] In this embodiment, the upper end 21a of the first protrusion 21 and the upper end 22a of the second protrusion 22 are formed in an angular shape in a cross-sectional view, but may also be formed as a surface parallel to the upper surface of the piezoelectric layer 2, as shown in Figure 13.

[0039] <Third embodiment> A third embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 4(a) is a plan view of a support substrate 1C of the third embodiment, and Fig. 4(b) is a CC cross-sectional view of an acoustic wave device 100C of the third embodiment. Parts with the same functions, names, and thicknesses as those of the first embodiment described above are designated by the same reference numerals, and descriptions thereof will be omitted.

[0040] In this embodiment, the first protrusion 21 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 21a, which serves as the central portion of the first protrusion 21, is provided at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1B to the bottom layer 13. The upper end 22a, which serves as the central portion of the second protrusion 22, is formed at the same height as the interface between the bottom layer 13 and the middle layer 12. The second protrusion 22 is lower than the first protrusion 21. The upper end 21a of the first protrusion 21 may be provided on the middle layer 12 or the top layer 11, and the upper end 22a of the second protrusion 22 may be disposed in the middle layer 12 or the bottom layer 13.

[0041] When the straight virtual line 51C in Fig. 4(a) is set as the cutting line (CC cutting line), the first protrusions 21 and the second protrusions 22 are alternately arranged in the cross-sectional view as shown in the cross-sectional view of Fig. 4(b). Note that in this embodiment, the cross-sectional view includes a line, such as the second protrusions 22, that is beyond the CC cutting line and is represented by a broken line.

[0042] In the plan view of FIG. 4(a), the upper ends 21a of the first protrusions 21 are aligned in a row along the imaginary lines 51C, 52C, and 53C in the X direction. The upper ends 22a of the second protrusions 22 are aligned in a row along the imaginary lines 54C, 55C, 56C, and 57C in the X direction. That is, two second protrusions 22 are arranged for one first protrusion 21 in the Y direction. Furthermore, in the Y direction, the upper ends 21a and 22a of the first protrusions 21 and the second protrusions 22 are aligned side by side, with their upper ends 21a and 22a parallel to the imaginary lines 41C, 42C, and 43C. Furthermore, in the X direction, the first protrusions 21 and the second protrusions 22 are arranged repeatedly, with the upper ends 21a of adjacent first protrusions 21 forming one cycle (the period from the imaginary line 41C to the imaginary line 43C being one cycle in the X direction). In addition, in the Y direction, the upper ends 21a of adjacent first protrusions 21 form one cycle (the period from imaginary line 51C to imaginary line 52C in the Y direction forms one cycle), and the first protrusions 21 and the second protrusions 22 are repeatedly arranged.

[0043] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0044] 4(a) has the second protrusions 22 denser than the configuration of the seventh embodiment in the plan view of Fig. 8 described later, and therefore the bulk waves from the piezoelectric layer 2 are scattered more effectively. From this perspective, it can be said that the third embodiment can suppress spurious signals more effectively than the first embodiment.

[0045] <Fourth embodiment> A fourth embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 5(a) is a plan view of a support substrate 1D of the fourth embodiment, and Fig. 5(b) is a DD cross-sectional view of an acoustic wave device 100D of the fourth embodiment. Parts with the same functions, names, and thicknesses as those of the first embodiment described above are assigned the same reference numerals, and descriptions thereof will be omitted.

[0046] As shown in FIG. 5(a), in this embodiment, the first protrusion 61 and the second protrusion 62 have a polygonal quadrangular shape. The first protrusion 61 penetrates the bottom layer 13 and reaches the middle layer 12. The top end 61a of the first protrusion 61, which serves as the center, is located at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 62 is formed from the top surface 31 of the support substrate 1D to the bottom layer 13. The top end 62a of the second protrusion 62, which serves as the center, is located at the same height as the interface between the bottom layer 13 and the middle layer 12. The second protrusion 62 is lower than the first protrusion 61. The top end 61a of the first protrusion 61 may be located on the middle layer 12 or the top layer 11, and the top end 62a of the second protrusion 62 may be located in the middle layer 12 or the bottom layer 13.

[0047] When the straight virtual line 51D in Figure 5(a) is set as the cutting line (DD cutting line), the first protrusions 61 and the second protrusions 62 are arranged alternately in cross-sectional view, as shown in the cross-sectional view of Figure 5(b).

[0048] In the plan view of FIG. 5(a), the upper ends 61a of the first protrusions 61 and the upper ends 62a of the second protrusions 62 are alternately aligned in a row along imaginary lines 51D, 52D, and 53D in the X direction. In the Y direction, the upper ends 61a and 62a of the first protrusions 61 and the second protrusions 62 are aligned parallel to imaginary lines 41D, 42D, and 43D. The first protrusions 61 and the second protrusions 62 are repeatedly arranged, with the imaginary lines 41D and 43D forming one cycle in the X direction. The first protrusions 61 and the second protrusions 62 are repeatedly arranged, with the imaginary lines 51D and 52D forming one cycle in the Y direction.

[0049] In this way, the first protrusions 61 and second protrusions 62 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the top surface of the support substrate as a rough surface. Furthermore, because the top ends 61a of the first protrusions 61 and the top ends 62a of the second protrusions 62 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0050] Fifth Embodiment A fifth embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 6(a) is a plan view of a support substrate 1E of the fifth embodiment, and Fig. 6(b) is an E-E cross-sectional view of an acoustic wave device 100E of the fifth embodiment. Parts with the same functions, names, and thicknesses as those of the first embodiment described above are designated by the same reference numerals, and descriptions thereof will be omitted.

[0051] As shown in FIG. 6( a), in this embodiment, the first protrusion 71 and the second protrusion 72 have a striped (stripe) shape in a plan view. The first protrusion 71 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 71a, which serves as the center of the first protrusion 71, is located at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 72 is formed from the top surface 31 of the support substrate 1E to the bottom layer 13. The upper end 72a of the second protrusion 72 is located at the same height as the interface between the bottom layer 13 and the middle layer 12. The second protrusion 72 is lower than the first protrusion 71. The upper end 71a, which serves as the center of the first protrusion 71, may be located in the middle layer 12 or the top layer 11, and the upper end 72a of the second protrusion 72 may be located in the middle layer 12 or the bottom layer 13.

[0052] When the straight virtual line 51E in Figure 6(a) is set as the cutting line (EE cutting line), the first protrusions 71 and the second protrusions 72 are arranged alternately in cross-sectional view, as shown in the cross-sectional view of Figure 6(b).

[0053] In the plan view of FIG. 6(a), the first protrusions 71 and the second protrusions 72 are repeatedly arranged with the distance in the X direction between adjacent upper ends 71a being one period in the X direction.

[0054] In this way, the first protrusions 71 and second protrusions 72 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur than when irregularities are formed on the top surface of the support substrate as a rough surface. Furthermore, because the top ends 71a of the first protrusions 71 and the top ends 72a of the second protrusions 72 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that prevents unexpected spurious signals from occurring due to irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0055] In this embodiment, the distance between the first protrusion 71 and the second protrusion 72 (on the upper surface 31a of the support substrate 1E in FIG. 6(b)) may be longer.

[0056] Sixth Embodiment A sixth embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 7(a) is a plan view of a support substrate 1F of the sixth embodiment, and Fig. 7(b) is an FF cross-sectional view of an acoustic wave device 100F of the sixth embodiment. Portions with the same functions, names, and thicknesses as those of the first embodiment described above are designated by the same reference numerals, and descriptions thereof will be omitted.

[0057] In this embodiment, the first protrusion 21 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 21a, which serves as the central portion of the first protrusion 21, is provided at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1F to the bottom layer 13. The upper end 22a, which serves as the central portion of the second protrusion 22, is formed at the same height as the interface between the bottom layer 13 and the middle layer 12. The second protrusion 22 is lower than the first protrusion 21. The upper end 21a of the first protrusion 21 may be provided on the middle layer 12 or the top layer 11, and the upper end 22a of the second protrusion 22 may be disposed in the middle layer 12 or the bottom layer 13.

[0058] When the straight virtual line 51F in Fig. 7(a) is set as the cutting line (FF cutting line), as shown in the cross-sectional view of Fig. 7(b), the first protrusions 21 and the second protrusions 22 are arranged in a regular and repeated pattern, with the distance between the upper ends 21a of the first protrusions 21 on adjacent straight lines 51F being one period. In this embodiment, the cross-sectional view includes a line, such as the second protrusions 22, that is beyond the FF cutting line and is represented by a broken line.

[0059] In the plan view of FIG. 7(a), the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are aligned in a row along imaginary lines 51F, 52F, 53F, and 54F in the X direction. In the Y direction, the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are aligned parallel to imaginary lines 41F, 42F, and 43F. The first protrusions 21 and the second protrusions 22 are aligned alternately in a row along all of these imaginary lines 41F, 42F, 43F, 51F, 52F, 53F, and 54F. In the X direction, the first protrusions 21 and the second protrusions 22 are aligned repeatedly, with the imaginary lines 41F to 43F forming one cycle in the X direction. In addition, in the Y direction, the first protrusions 21 and the second protrusions 22 are arranged with the virtual line 51F to the virtual line 52F forming one period in the Y direction. Furthermore, as shown by the virtual line 101, the second protrusions are arranged in a regular quadrangle shape with the first protrusion 21 at the center.

[0060] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0061] 7(a) has the second protrusions 22 denser than the configuration of the eighth embodiment shown in Fig. 9(a) described later, and therefore the bulk waves from the piezoelectric layer 2 are scattered more effectively. From this perspective, it can be said that this embodiment (sixth embodiment) can suppress spurious signals more effectively than the eighth embodiment.

[0062] Seventh Embodiment A seventh embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 8(a) is a plan view of a support substrate 1G of the seventh embodiment, and Fig. 8(b) is a GG cross-sectional view of an acoustic wave device 100G of the seventh embodiment. Portions with the same functions, names, and thicknesses as those of the first embodiment described above are designated by the same reference numerals, and descriptions thereof will be omitted.

[0063] In this embodiment, the first protrusion 21 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 21a, which serves as the central portion of the first protrusion 21, is provided at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1G to the bottom layer 13. The upper end 22a, which serves as the central portion of the second protrusion 22, is formed at the same height as the interface between the bottom layer 13 and the middle layer 12. The second protrusion 22 is lower than the first protrusion 21. The upper end 21a of the first protrusion 21 may be provided on the middle layer 12 or the top layer 11, and the upper end 22a of the second protrusion 22 may be disposed in the middle layer 12 or the bottom layer 13.

[0064] When the straight imaginary line 51G in Fig. 8(a) is set as the cutting line (GG cutting line), as shown in the cross-sectional view of Fig. 8(b), the first protrusions 21 and the second protrusions 22 are arranged in a regular and repeated pattern, with the distance between the upper ends 21a of adjacent first protrusions 21 on the imaginary line 51G being one period. In this embodiment, the cross-sectional view includes a line, such as the second protrusions 22, that is beyond the GG cutting line and is represented by a broken line.

[0065] In the plan view of FIG. 8(a), the upper ends 21a of the first protrusions 21 are aligned in a row along imaginary lines 51G, 52G, and 53G in the X direction. The upper ends 22a of the second protrusions 22 are aligned in a row along imaginary lines 54G, 55G, 56G, 57G, and 58G in the X direction. In the Y direction, the upper ends 21a of the first protrusions 21 are aligned parallel to imaginary lines 41G and 43G. The upper ends 22a of the second protrusions 22 are aligned parallel to imaginary lines 42G and 44G. In the X direction, the distance from imaginary line 41G to imaginary line 43G forms one period in the X direction, and two second protrusions 22 are repeatedly arranged for one first protrusion 21 per period. In addition, in the Y direction, with the imaginary line 51G to the imaginary line 53G being one period in the Y direction, two second protrusions 22 are arranged relative to two first protrusions 21 per period.

[0066] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the imaginary lines 51G, 52G, and 53G in the X direction is repeated at the same period in the X direction, and the arrangements along the imaginary lines 51G and 53G have the same position in the X direction, while the arrangement along the imaginary line 52G has a different position in the X direction from the arrangements along the imaginary lines 51G and 53G. This will be explained below.

[0067] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the imaginary line 51G in the X direction is formed by the first protrusions 21 along the imaginary line 51G and the second protrusions 22 along the imaginary lines 54G and 55G. The repeated arrangement of the first protrusions 21 and the second protrusions 22 along the imaginary line 52G in the X direction is formed by the first protrusions 21 along the imaginary line 52G and the second protrusions 22 along the imaginary lines 56G and 57G. The repeated arrangement of the first protrusions 21 and the second protrusions 22 along the imaginary line 53G in the X direction is formed by the first protrusions 21 along the imaginary line 53G and the second protrusions 22 along the imaginary lines 58G and 59G.

[0068] The repeated arrangement of the first protrusions 21 and the second protrusions 22 in the X direction along these imaginary lines 51G, 52G, and 53G is such that two second protrusions 22 are arranged vertically (in the Y direction) between each pair of first protrusions 21.

[0069] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the virtual lines 51G and 53G, which are two adjacent virtual lines, is provided in the same manner in the X direction. In contrast, the repeated arrangement of the first protrusions 21 and the second protrusions 22 along the virtual line 52G is provided at a different position in the X direction from the repeated arrangement of the first protrusions 21 and the second protrusions 22 along the virtual lines 51G and 53G, which are one adjacent virtual line to the virtual line 52G, but is the same arrangement per period (for example, the virtual line 41G to the virtual line 43G is one period in the X direction).

[0070] In this embodiment, only one period in the Y direction is shown in Figure 8(a), but this is for simplification, and two or more periods of first protrusions 21 and second protrusions 22 may be provided in the Y direction.

[0071] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0072] Eighth Embodiment An eighth embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 9(a) is a plan view of a support substrate 1H of the eighth embodiment, and Fig. 9(b) is an HH cross-sectional view of an acoustic wave device 100H of the eighth embodiment. Portions with the same functions, names, and thicknesses as those of the first embodiment described above are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0073] In this embodiment, the first protrusion 21 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 21a, which serves as the central portion of the first protrusion 21, is provided at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1H to the bottom layer 13. The upper end 22a, which serves as the central portion of the second protrusion 22, is formed at the same height as the interface between the bottom layer 13 and the middle layer 12. The upper end 21a of the first protrusion 21 may be provided on the middle layer 12 or the top layer 11, and the upper end 22a of the second protrusion 22 may be disposed in the middle layer 12 or the bottom layer 13.

[0074] When the straight imaginary line 51H in FIG. 9(a) is set as the cutting line (HH cutting line), as shown in the cross-sectional view of FIG. 9(b), between the first protrusions 21 of equal size in the cross-sectional view, there is provided an upper end 21a of one first protrusion 21 and two second protrusions 22, as indicated by the dashed lines. That is, in the cross-sectional view, the first protrusions 21 and the second protrusions 22 are arranged in a regular, repeated pattern, with the distance between the upper ends 21a of adjacent first protrusions 21 on the imaginary line 51 being one period. In this embodiment, the cross-sectional view is considered to include a line beyond the HH cutting line, such as the second protrusions 22, which is represented by a dashed line in FIG. 9(b).

[0075] In the plan view of FIG. 9( a), the upper ends 21a of the first protrusions 21 are aligned in a row along the imaginary lines 51H, 52H, and 53H in the X direction. The upper ends 22a of the second protrusions 22 are aligned in a row along the imaginary lines 54H, 55H, 56H, 57H, 58H, and 59H in the X direction. In the Y direction, the upper ends 21a of the first protrusions 21 are aligned parallel to the imaginary lines 41H and 42H. In the X direction, the imaginary lines 41H and 42H form one cycle in the X direction, and two second protrusions 22 are arranged repeatedly for one first protrusion 21 per cycle. In the Y direction, the imaginary lines 51H and 53H form one cycle in the Y direction, and two second protrusions 22 are arranged for two first protrusions 21 per cycle.

[0076] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the imaginary lines 51H, 52H, and 53H in the X direction is repeated at the same period in the X direction, and the arrangements along the imaginary lines 51H and 53H have the same position in the X direction, while the arrangement along the imaginary line 52H has a different position in the X direction from the arrangements along the imaginary lines 51H and 53H. This will be described below.

[0077] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the imaginary line 51H in the X direction is formed by the first protrusions 21 along the imaginary line 51H and the second protrusions 22 along the imaginary lines 54H and 55H. The repeated arrangement of the first protrusions 21 and the second protrusions 22 along the imaginary line 52H in the X direction is formed by the first protrusions 21 along the imaginary line 52H and the second protrusions 22 along the imaginary lines 56H and 57H. The repeated arrangement of the first protrusions 21 and the second protrusions 22 along the imaginary line 53H in the X direction is formed by the first protrusions 21 along the imaginary line 53H and the second protrusions 22 along the imaginary lines 58H and 59H.

[0078] The repeated arrangement of the first protrusions 21 and the second protrusions 22 in the X direction along these virtual lines 51H, 52H, and 53H is such that two second protrusions 22 are arranged diagonally (at different positions in the Y and X directions) between each pair of first protrusions 21.

[0079] Furthermore, as shown by the imaginary line 102, the second protrusions 22 are arranged in a square shape with the first protrusion 21 at the center.

[0080] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the virtual lines 51H and 53H, which are two adjacent virtual lines, is provided in the same manner in the X direction. In contrast, the repeated arrangement of the first protrusions 21 and the second protrusions 22 along the virtual line 52H is provided at a different position in the X direction from the repeated arrangement of the first protrusions 21 and the second protrusions 22 along the virtual lines 51H and 53H, which are one adjacent virtual line to the virtual line 52H, but is the same arrangement per period (for example, the virtual line 41H to the virtual line 42H is one period in the X direction).

[0081] In this embodiment, only one period in the Y direction is shown in Figure 9(a), but this is for simplification, and two or more periods of first protrusions 21 and second protrusions 22 may be provided in the Y direction.

[0082] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0083] Ninth Embodiment A ninth embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 10(a) is a plan view of a support substrate 1J of the ninth embodiment, and Fig. 10(b) is a cross-sectional view of an acoustic wave device 100J of the ninth embodiment. Portions with the same functions, names, and thicknesses as those of the first embodiment described above are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0084] In this embodiment, the first protrusion 21 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 21a, which serves as the central portion of the first protrusion 21, is provided at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1J to the bottom layer 13. The upper end 22a, which serves as the central portion of the second protrusion 22, is formed at the same height as the interface between the bottom layer 13 and the middle layer 12. The upper end 21a of the first protrusion 21 may be provided on the middle layer 12 or the top layer 11, and the upper end 22a of the second protrusion 22 may be disposed in the middle layer 12 or the bottom layer 13.

[0085] When the straight imaginary line 51J in FIG. 10(a) is set as a cutting line (JJ cutting line), as shown in the cross-sectional view of FIG. 10(b), between each pair of first protrusions 21 of equal size, an upper end 21a of one first protrusion 21 and two second protrusions 22 are provided, as indicated by the dashed lines. That is, in the cross-sectional view, the first protrusions 21 and the second protrusions 22 are arranged in a regular, repeated pattern, with the distance between the upper ends 21a of the first protrusions 21 on adjacent imaginary line 51J being one period. In this embodiment, the cross-sectional view includes a line beyond the JJ cutting line, such as the second protrusions 22, which is represented by a dashed line in FIG. 10(b).

[0086] In the plan view of FIG. 10(a), the upper ends 21a of the first protrusions 21 are aligned in a row along imaginary lines 51J, 52J, and 53J in the X direction. The upper ends 22a of the second protrusions 22, which are central portions of the first protrusions 21, are aligned in a row along imaginary lines 81J, 82J, and 83J that are inclined with respect to the X direction, as shown in FIG. 9(b) above, although imaginary lines parallel to the Y direction are omitted. The upper ends 21a of the first protrusions 21 are also aligned in a row along imaginary lines 81J, 82J, and 83J that are inclined with respect to the X direction. The upper ends 22a of the second protrusions 22, which are central portions of the second protrusions 22, are aligned in a row along imaginary lines 91J, 92J, 93J, 94J, and 95J that are inclined with respect to the X direction. In the Y direction, the upper ends 21a of the first protrusions 21 are aligned in a row parallel to imaginary lines 41J, 42J, and 43J. In addition, in the X direction, the first protrusions 21 and the second protrusions 22 are repeatedly arranged with one period in the X direction from the virtual line 41J to the virtual line 43J. In addition, in the Y direction, the first protrusions 21 and the second protrusions 22 are arranged with one period in the Y direction from the virtual line 51J to the virtual line 53J.

[0087] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the virtual lines 51J, 52J, and 53J in the X direction is repeated at the same period in the X direction, and the virtual lines 51J and 53J are in the same position in the X direction, while the virtual line 52J is in a different position in the X direction from 51J and 53J. This will be explained below.

[0088] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the imaginary line 51J in the X direction is formed by the first protrusions 21 along the imaginary line 51J and the second protrusions 22 along the imaginary lines 54J and 55J. The repeated arrangement of the first protrusions 21 and the second protrusions 22 along the imaginary line 52J in the X direction is formed by the first protrusions 21 along the imaginary line 52J and the second protrusions 22 along the imaginary lines 56J and 57J. The repeated arrangement of the first protrusions 21 and the second protrusions 22 along the imaginary line 53J in the X direction is formed by the first protrusions 21 along the imaginary line 53J and the second protrusions 22 along the imaginary lines 58J and 59J.

[0089] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 in the X direction along these imaginary lines 51J, 52J, and 53J is such that two second protrusions 22 are arranged diagonally (at different positions in the Y and X directions) between each first protrusion 21. Furthermore, the two diagonally arranged second protrusions 22 are arranged so as to be on a straight line along the imaginary lines 91J, 92J, and 93J.

[0090] The repeated arrangement (pattern) of the first protrusions 21 and the second protrusions 22 along the virtual lines 51J and 53J, which are two adjacent virtual lines, is provided in the same manner in the X direction. In contrast, the repeated arrangement of the first protrusions 21 and the second protrusions 22 along the virtual line 52J is provided at a different position in the X direction from the repeated arrangement of the first protrusions 21 and the second protrusions 22 along the virtual lines 51J and 53J, which are one adjacent virtual line to the virtual line 52J, but is the same arrangement per period (for example, the virtual line 41J to the virtual line 43J is one period in the X direction).

[0091] In this embodiment, only one period in the Y direction is shown in Figure 10(a), but this is for simplification, and two or more periods of first protrusions 21 and second protrusions 22 may be provided in the Y direction.

[0092] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0093] Tenth Embodiment A tenth embodiment will be described as an embodiment of an acoustic wave device of the present invention. Fig. 11(a) is a plan view of a support substrate 1K of the tenth embodiment, and Fig. 11(b) is a KK cross-sectional view of an acoustic wave device 100K of the tenth embodiment. Portions with the same functions, names, and thicknesses as those of the first embodiment described above are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0094] In this embodiment, the first protrusion 21 penetrates the bottom layer 13 and reaches the middle layer 12. The upper end 21a, which serves as the central portion of the first protrusion 21, is provided at the same height as the interface between the top layer 11 and the middle layer 12. The second protrusion 22 is formed from the upper surface 31 of the support substrate 1B to the bottom layer 13. The upper end 22a, which serves as the central portion of the second protrusion 22, is formed at the same height as the interface between the bottom layer 13 and the middle layer 12. The upper end 21a of the first protrusion 21 may be provided on the middle layer 12 or the top layer 11, and the upper end 22a of the second protrusion 22 may be disposed in the middle layer 12 or the bottom layer 13.

[0095] When the straight virtual line 51K in Fig. 11(a) is set as the cutting line (KK cutting line), as shown in the cross-sectional view of Fig. 11(b), the first protrusions 21 and the second protrusions 22 are arranged regularly and repeatedly, with the distance between the upper ends 21a of adjacent first protrusions 21 on the straight line 51K being one period, as shown by the solid and dashed lines. In this embodiment, the cross-sectional view includes a line beyond the KK cutting line, such as the second protrusions 22, which is represented by a dashed line in Fig. 11(b).

[0096] In the plan view of FIG. 11(a), the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are alternately aligned in a row along imaginary lines 51K, 52K, and 53K in the X direction. Only the upper ends 22a of the second protrusions 22 are aligned in a row along imaginary lines 54K and 55K in the X direction. That is, there are rows along imaginary lines 51K, 52K, and 53K in which the first protrusions 21 and the second protrusions 22 are alternately aligned in the X direction, and rows along imaginary lines 54K and 55K in which only the second protrusions 22 are aligned in a row in the X direction. Furthermore, in the Y direction, the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are aligned in a row parallel to imaginary lines 41K and 42K. In addition, in the X direction, the first protrusions 21 and the second protrusions 22 are repeatedly arranged with the virtual line 41K to the virtual line 42K as one cycle in the X direction. In addition, in the Y direction, the first protrusions 21 and the second protrusions 22 are arranged with the virtual line 51K to the virtual line 53K as one cycle in the Y direction. Furthermore, as shown by the virtual line 103, six second protrusions 22 are provided equidistantly and equiangularly around the first protrusion 21. That is, the second protrusions are arranged in a regular hexagonal shape.

[0097] In this way, the first protrusions 21 and second protrusions 22 protruding from the support substrate 1 are periodically and repeatedly arranged in a plan view, so unexpected spurious signals caused by the irregularities in some locations are less likely to occur compared to when irregularities are formed on the upper surface of the support substrate as a rough surface. Furthermore, because the upper ends 21a of the first protrusions 21 and the upper ends 22a of the second protrusions 22 are at different heights, bulk waves from the piezoelectric layer 2 are scattered more effectively than when all the protrusions are the same height. Therefore, an acoustic wave device can be configured that can prevent unexpected spurious signals caused by irregularities, while scattering bulk waves more effectively and suppressing spurious signals.

[0098] In the above embodiment, the first protrusions 21 and second protrusions 22 of the support substrate of the acoustic wave device of the present invention are described as having conical shapes, and the first protrusions 61 (see FIG. 5(a)) and second protrusions 62 (see FIG. 5(a)) are described as having quadrangular shapes. However, other polygonal shapes, such as hexagonal or triangular pyramid shapes, are also applicable. The arrangement direction (propagation direction) of the electrode fingers is the X direction, and the extension direction of the electrode fingers is the Y direction. However, from the viewpoint of scattering of bulk waves, the first protrusions 21, 61 and second protrusions 22, 62 may be configured so as to be regularly and repeatedly arranged in a cross section taken along a virtual line inclined from the X direction and the Y direction, as shown by virtual line 66J in FIG. 10(a).

[0099] The present invention has been described above, but when implementing the present invention, it is not limited to the above-described examples, and various modifications and additions are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0100] 1 Support substrate 2 Piezoelectric layer 4 electrode layer 5. Middle class 6 recess 11 Top Floor 12 Middle class 13 Bottom Floor 21 1st protrusion 21a Upper end (center) of the first protrusion 22 Second protrusion 22a Upper end (center) of second protrusion 31 Upper surface of support substrate 1 100, 100B, 100C, 100D, 100E, 100F, 100G, 100H, 100J, 100K Acoustic Wave Device

Claims

1. a support substrate having a plurality of protrusions; an intermediate layer disposed on the support substrate so as to fill recesses formed between the protrusions; a piezoelectric layer disposed on the intermediate layer opposite the support substrate; an electrode layer disposed on the piezoelectric layer opposite the intermediate layer; Equipped with The plurality of protrusions includes a plurality of first protrusions and a plurality of second protrusions that are lower in height than the first protrusions. Acoustic wave devices.

2. The plurality of first protrusions and the plurality of second protrusions are arranged in a repeated and regular pattern in a cross-sectional view taken along a line connecting the centers of adjacent first protrusions in a plan view, with the distance between the centers of adjacent first protrusions being one period. The acoustic wave device according to claim 1 .

3. The plurality of first protrusions and the plurality of second protrusions are alternately arranged in a cross-sectional view taken along a straight line. The acoustic wave device according to claim 1 .

4. the intermediate layer includes a top layer in contact with the piezoelectric layer, a bottom layer in contact with the support substrate, and a middle layer interposed between the top layer and the bottom layer; The first protrusions penetrate the bottom layer, and upper ends of the first protrusions are provided on the middle layer. The acoustic wave device according to claim 2 .

5. the intermediate layer includes a top layer in contact with the piezoelectric layer, a bottom layer in contact with the support substrate, and a middle layer interposed between the top layer and the bottom layer; The first protrusions penetrate the bottom layer and the middle layer, and upper ends of the first protrusions are located on the top layer. The acoustic wave device according to claim 2 .

6. the intermediate layer includes a top layer in contact with the piezoelectric layer, a bottom layer in contact with the support substrate, and a middle layer interposed between the top layer and the bottom layer; The upper ends of the second protrusions are located on the lowermost layer. The acoustic wave device according to claim 2 or 3.

7. The first protrusion and the second protrusion have a conical or polygonal shape. The acoustic wave device according to claim 2 or 3.

8. The first protrusions and the second protrusions are striped in plan view. The acoustic wave device according to claim 2 or 3.

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