Elastic wave device

Abstract

The present invention provides an elastic wave device capable of suppressing transverse modes and high-order modes. The elastic wave device (1) of the present invention comprises a piezoelectric substrate (2) and an IDT electrode (7). The IDT electrode (7) comprises a central region (C) and a first edge region (E1) and a second edge region (E2). The regions including the first edge region (E1) and the second edge region (E2) and overlapping with the regions in the direction of propagation of the elastic wave are the first extended edge region (Ex1) and the second extended edge region (Ex2). The first extended edge region (Ex1) and the second extended edge region (Ex2) are provided with a first sound velocity adjustment portion (L) and a second sound velocity adjustment portion (M) having a lower sound velocity than the central region (C). The first sound velocity adjustment portion (L) comprises a first end portion (La) and a second end portion (Lb), and the second sound velocity adjustment portion (M) comprises a third end portion (Ma) and a fourth end portion (Mb). The first end portion (La) to the fourth end portion (Mb) are located outside the first edge region (E1) and the second edge region (E2). At least one of the two sets of ends, the first end portion (La) and the third end portion (Ma) and the second end portion (Lb) and the fourth end portion (Mb), do not overlap in the direction in which the plurality of electrode fingers extend.

Description

Technical Field

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

[0002] Previously, elastic wave devices have been widely used in filters for portable telephones, etc. Patent Document 1 discloses an example of an elastic wave device. In this elastic wave device, IDT (Interdigital Transducer) electrodes are provided on a piezoelectric substrate. Furthermore, a silicon oxide film is provided on the piezoelectric substrate, covering the IDT electrodes. A mass-addition film is provided on the silicon oxide film, overlapping the leading ends of the plurality of electrode fingers of the IDT electrodes when viewed from above.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-068309 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In Patent Document 1, by enabling the piston mode, stray noise caused by the transverse mode can be suppressed. However, it is difficult to suppress even higher-order modes.

[0008] The purpose of this invention is to provide a device for suppressing elastic waves of transverse and higher-order modes.

[0009] Technical solutions for solving the problem

[0010] The elastic wave device of the present invention comprises: a piezoelectric substrate; an IDT electrode disposed on the piezoelectric substrate and having a plurality of electrode fingers; and a first reflector and a second reflector, which are a pair of reflectors disposed on both sides of the IDT electrode on the piezoelectric substrate in the elastic wave propagation direction. The portions of adjacent electrode fingers of the IDT electrode that overlap each other in the elastic wave propagation direction form an intersection region. The intersection region has: a central region located at the center side in the direction in which the plurality of electrode fingers extend; and a pair of edge regions disposed on both sides of the central region in the direction in which the plurality of electrode fingers extend. A region including the pair of edge regions and overlapping the pair of edge regions in the elastic wave propagation direction forms a pair of extended edge regions. A pair of sound velocity adjustment parts are provided in the edge region, the sound velocity in the pair of sound velocity adjustment parts is lower than the sound velocity in the central region, one of the pair of sound velocity adjustment parts has a first end located on the side of the first reflector and a second end located on the side of the second reflector, the other of the pair of sound velocity adjustment parts has a third end located on the side of the first reflector and a fourth end located on the side of the second reflector, the first end, the second end, the third end and the fourth end are located outside the pair of edge regions in the direction of elastic wave propagation, and at least one of the two sets of ends, the first end and the third end and the second end and the fourth end, does not overlap in the direction in which the plurality of electrode fingers extend.

[0011] Effects of the Invention

[0012] The elastic wave device according to the present invention can suppress transverse modes and higher-order modes. Attached Figure Description

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

[0014] Figure 2 This is a cross-sectional view showing the elastic wave device according to the first embodiment of the present invention, through the first extended edge region.

[0015] Figure 3 It is along Figure 1 A sectional view along line II in the diagram.

[0016] Figure 4 This is a cross-sectional view showing the elastic wave device according to the first embodiment of the present invention, through the second extended edge region.

[0017] Figure 5 This is a cross-sectional view showing the elastic wave device according to the first embodiment of the present invention, through a section of the central region.

[0018] Figure 6 This is a top view of an elastic wave device according to a first variation of the first embodiment of the present invention.

[0019] Figure 7 This is a top view of an elastic wave device according to a second variation of the first embodiment of the present invention.

[0020] Figure 8 This is a top view of the elastic wave device according to the third variation of the first embodiment of the present invention.

[0021] Figure 9 This is a top view of the elastic wave device according to the fourth variation of the first embodiment of the present invention.

[0022] Figure 10 This is a top view of the elastic wave device according to the fifth variation of the first embodiment of the present invention.

[0023] Figure 11 This is a top view of the elastic wave device according to the sixth variation of the first embodiment of the present invention.

[0024] Figure 12 This is a cross-sectional view showing the elastic wave device according to the seventh variation of the first embodiment of the present invention, through the first extended edge region.

[0025] Figure 13 This is a cross-sectional view showing the elastic wave device according to the eighth variation of the first embodiment of the present invention, through the first extended edge region.

[0026] Figure 14 This is a cross-sectional view showing the elastic wave device according to the ninth variation of the first embodiment of the present invention, through the first extended edge region.

[0027] Figure 15 This is a cross-sectional view showing the elastic wave device according to the 10th variation of the first embodiment of the present invention, through the first extended edge region.

[0028] Figure 16 This is a cross-sectional view showing the elastic wave device according to the second embodiment of the present invention, through the first extended edge region.

[0029] Figure 17 This is a top view of the elastic wave device according to the third embodiment of the present invention. Detailed Implementation

[0030] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0031] In addition, it should be noted that the embodiments described in this specification are illustrative and that partial substitutions or combinations of structures can be made between different embodiments.

[0032] Figure 1 This is a top view of the elastic wave device according to the first embodiment of the present invention.

[0033] In the elastic wave device 1, the transverse mode is suppressed by establishing a piston mode. The elastic wave device 1 has a piezoelectric substrate 2. An IDT electrode 7 is provided on the piezoelectric substrate 2. The IDT electrode 7 has multiple electrode fingers. A central region C, a first edge region E1, and a second edge region E2 are arranged in the IDT electrode 7. The first edge region E1 and the second edge region E2 contain the tips of the multiple electrode fingers. Furthermore, in the elastic wave device 1, the first edge region E1 and the second edge region E2 extend to the outside of the IDT electrode 7. These regions are the first extended edge region Ex1 and the second extended edge region Ex2. A first sound velocity adjustment unit L and a second sound velocity adjustment unit M are provided in the first extended edge region Ex1 and the second extended edge region Ex2. As a result, the piston mode is established.

[0034] The first sound velocity adjustment unit L has a first end La and a second end Lb. The second sound velocity adjustment unit M has a third end Ma and a fourth end Mb. Here, the feature of this embodiment is that the elastic wave device 1 has the following structure: 1) The first sound velocity adjustment unit L is provided in the first extended edge region Ex1, and the second sound velocity adjustment unit M is provided in the second extended edge region Ex2. 2) At least one of the two sets of ends, the first end La and the third end Ma, and the second end Lb and the fourth end Mb, does not overlap in the direction in which the plurality of electrode fingers extend. Therefore, not only transverse modes can be suppressed, but also higher-order modes can be suppressed. Hereinafter, details of the above-mentioned effects will be explained together with details of the structure of this embodiment.

[0035] Figure 2 This is a cross-sectional view showing the elastic wave device according to the first embodiment, through the first extended edge region.

[0036] like Figure 2 As shown, the piezoelectric substrate 2 has a support substrate 3, a high-velocity film 4 as a high-velocity material layer, a low-velocity film 5, and a piezoelectric layer 6. More specifically, the high-velocity film 4 is disposed on the support substrate 3. The low-velocity film 5 is disposed on the high-velocity film 4. The piezoelectric layer 6 is disposed on the low-velocity film 5.

[0037] The aforementioned IDT electrode 7 is disposed on the piezoelectric layer 6 of the piezoelectric substrate 2. An elastic wave is excited by applying an alternating voltage to the IDT electrode 7. Figure 2As shown, a pair of reflectors are provided on both sides of the elastic wave propagation direction of the IDT electrode 7 on the piezoelectric substrate 2. More specifically, the pair of reflectors are a first reflector 8 and a second reflector 9. In this way, the elastic wave device 1 of this embodiment is a surface acoustic wave resonator. However, the elastic wave device of the present invention is not limited to an elastic wave resonator, and may also be a filter device or a multiplexer having an elastic wave resonator.

[0038] like Figure 1 As shown, the IDT electrode 7 has a first busbar 14, a second busbar 15, a plurality of first electrode fingers 16, and a plurality of second electrode fingers 17. The first busbar 14 and the second busbar 15 are opposite to each other. One end of each of the plurality of first electrode fingers 16 is connected to the first busbar 14. One end of each of the plurality of second electrode fingers 17 is connected to the second busbar 15. The plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 are interleaved with each other. In addition, in this specification, the direction of elastic wave propagation is defined as the x-direction. The direction in which the first electrode fingers 16 and the second electrode fingers 17 extend is defined as the y-direction. In this embodiment, the x-direction and the y-direction are orthogonal.

[0039] The first reflector 8 has multiple electrode fingers 18. The second reflector 9 has multiple electrode fingers 19. In this specification, the first electrode finger 16, the second electrode finger 17 of the IDT electrode 7, the electrode fingers 18 of the first reflector 8, and the electrode fingers 19 of the second reflector 9 are sometimes collectively referred to as electrode fingers. The IDT electrode 7, the first reflector 8, and the second reflector 9 contain suitable metal. The IDT electrode 7, the first reflector 8, and the second reflector 9 may also contain stacked metal films, or they may contain a single-layer metal film.

[0040] As Figure 2 The material of the piezoelectric layer 6 shown can be, for example, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate).

[0041] The low-velocity membrane 5 is a membrane with relatively low sound speed. More specifically, the sound speed of the bulk wave propagating in the low-velocity membrane 5 is lower than the sound speed of the bulk wave propagating in the piezoelectric layer 6. As a material for the low-velocity membrane 5, for example, glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum pentoxide, or a compound of silicon oxide with added fluorine, carbon, or boron as the main component can be used.

[0042] In this embodiment, the hypersonic material layer is a hypersonic film 4. The hypersonic material layer is a layer with relatively high sound speeds. More specifically, the sound speed of the bulk wave propagating in the hypersonic material layer is higher than the sound speed of the elastic wave propagating in the piezoelectric layer 6. As the material for the hypersonic film 4, for example, silicon, alumina, silicon carbide, silicon nitride, silicon oxynitride, sapphire, lithium tantalate, lithium niobate, quartz, bauxite, zirconium oxide, cordierite, mullite, block talc, forsterite, magnesium oxide, DLC (diamond-like carbon) film, or diamond, or a medium with the above materials as the main component, can be used.

[0043] As the material for the support substrate 3, for example, various ceramics such as alumina, lithium tantalate, lithium niobate, piezoelectric materials such as quartz, bauxite, sapphire, magnesium oxide, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, block talc, and forsterite, dielectrics such as diamond and glass, semiconductors such as silicon and gallium nitride, or resins can also be used.

[0044] In this embodiment, the piezoelectric substrate 2 has a structure in which a high-velocity film 4, a low-velocity film 5, and a piezoelectric layer 6 are sequentially stacked as high-velocity material layers. This allows the energy of elastic waves to be effectively contained within the piezoelectric layer 6.

[0045] Alternatively, a protective film can be provided on the piezoelectric substrate 2 to cover the IDT electrode 7, the first reflector 8, and the second reflector 9. In this case, the IDT electrode 7, the first reflector 8, and the second reflector 9 are less prone to damage. For the protective film, for example, a dielectric such as silicon oxide, silicon nitride, or silicon oxynitride can be used.

[0046] Figure 3 It is along Figure 1 A sectional view along line II in the diagram. Figure 4 This is a cross-sectional view showing the elastic wave device according to the first embodiment, through the second extended edge region. Figure 5 This is a cross-sectional view showing the elastic wave device according to the first embodiment, through the central region.

[0047] like Figure 1 as well as Figure 3 As shown, in the IDT electrode 7, the portion where the first electrode finger 16 and the second electrode finger 17 overlap in the x-direction is a cross region A. Cross region A has a central region C and a pair of edge regions. More specifically, the pair of edge regions are the aforementioned first edge region E1 and the aforementioned second edge region E2. The central region C is located on the central side in the y-direction within cross region A. The first edge region E1 and the second edge region E2 are disposed on opposite sides of the central region C in the y-direction. More specifically, the first edge region E1 is disposed on the side of the first busbar 14 of the central region C. The second edge region E2 is disposed on the side of the second busbar 15 of the central region C.

[0048] The IDT electrode 7 has a first spacer region G1 and a second spacer region G2. The first spacer region G1 is located between the first edge region E1 and the first busbar 14. The second spacer region G2 is located between the second edge region E2 and the second busbar 15. In the first spacer region G1, only the first electrode finger 16 and the second electrode finger 17 are provided. Therefore, the sound speed in the first spacer region G1 is higher than the sound speed in the central region C. Similarly, in the second spacer region G2, only the second electrode finger 17 and the first electrode finger 16 are provided. Therefore, the sound speed in the second spacer region G2 is higher than the sound speed in the central region C. Let the sound speed in the central region C be Vc, and the sound speed in the first spacer region G1 and the second spacer region G2 be Vg. In this way, a high sound speed region is formed in the first spacer region G1 and the second spacer region G2.

[0049] Here, a pair of extended edge regions refers to a region that includes a pair of edge regions and overlaps with the pair of edge regions in the direction of elastic wave propagation. More specifically, as... Figure 2 As shown, the region containing the first edge region E1 and overlapping with the first edge region E1 in the x-direction is the aforementioned first extended edge region Ex1. Figure 4 As shown, the region containing the second edge region E2 and overlapping with the second edge region E2 in the x-direction is the aforementioned second extended edge region Ex2. On the other hand, as... Figure 5 As shown, the region that includes the central region C and overlaps with the central region C in the x direction is the extended central region Cx.

[0050] Return to Figure 1 A pair of sound velocity adjustment units are provided in a pair of extended edge regions. More specifically, the first sound velocity adjustment unit L is provided in the first extended edge region Ex1. The second sound velocity adjustment unit M is provided in the second extended edge region Ex2.

[0051] The first sound velocity adjustment section L extends to the outer side of the first reflector 8 and the second reflector 9 in the x-direction. The sound velocity in the first sound velocity adjustment section L is lower than the sound velocity in the central region C. In this embodiment, the first sound velocity adjustment section L is constructed by providing a mass-addition film 12. The mass-addition film 12 has a strip-like shape. One mass-addition film 12 is provided on all the electrode fingers of the IDT electrode 7, the first reflector 8, and the second reflector 9. Furthermore, the mass-addition film 12 is also provided on portions between the plurality of electrode fingers on the piezoelectric substrate 2, portions between the IDT electrode 7 and the first reflector 8, and portions between the IDT electrode 7 and the second reflector 9. The direction in which the first sound velocity adjustment section L extends is parallel to the x-direction.

[0052] The second sound velocity adjustment section M extends to the outer side of the first reflector 8 and the second reflector 9 in the x-direction. The sound velocity in the second sound velocity adjustment section M is lower than the sound velocity in the central region C. In this embodiment, the second sound velocity adjustment section M is constructed by providing a mass-added film 13. The mass-added film 13 has a strip-like shape. One mass-added film 13 is provided on all the electrode fingers of the IDT electrode 7, the first reflector 8, and the second reflector 9. Furthermore, the mass-added film 13 is also provided on portions between multiple electrode fingers on the piezoelectric substrate 2, portions between the IDT electrode 7 and the first reflector 8, and portions between the IDT electrode 7 and the second reflector 9. The direction in which the second sound velocity adjustment section M extends is parallel to the x-direction. Suitable dielectrics, etc., can be used for the mass-added film 12 and the mass-added film 13.

[0053] The first sound velocity adjustment unit L has a first end La and a second end Lb. The first end La is located on the side of the first reflector 8. The second end Lb is located on the side of the second reflector 9. The second sound velocity adjustment unit M has a third end Ma and a fourth end Mb. The third end Ma is located on the side of the first reflector 8. The fourth end Mb is located on the side of the second reflector 9. In this embodiment, the first end La, the second end Lb, the third end Ma, and the fourth end Mb are located on the outer side of the pair of reflectors in the x-direction.

[0054] Furthermore, the first end La, the second end Lb, the third end Ma, and the fourth end Mb only need to be located outside the IDT electrode 7 in the x-direction. This allows the sound velocity in the pair of edge regions to be lower than the sound velocity in the central region C.

[0055] In this embodiment, the regions in the y-direction are arranged in the order of a central region C, a pair of sound velocity adjustment units, and a pair of high-sound velocity regions. This establishes a piston mode, which can suppress transverse modes.

[0056] Here, the dimension of the sound velocity adjustment section along the direction in which it extends is defined as its length. The second sound velocity adjustment section M is longer than the first sound velocity adjustment section L. More specifically, the third end Ma is located on the outer side in the x-direction compared to the first end La. The fourth end Mb is located on the outer side in the x-direction compared to the second end Lb. Thus, in this embodiment, the first end La and the third end Ma, and the second end Lb and the fourth end Mb do not overlap in the y-direction. As a result, higher-order modes can also be suppressed. This will be explained below.

[0057] The primary mode resonates in the region where the IDT electrode 7 and a pair of reflectors are located. Therefore, most of the energy of the primary mode is concentrated in the region where the IDT electrode 7 and the pair of reflectors are located. On the other hand, the higher-order modes resonate in the thickness direction of the piezoelectric layer 6. Therefore, the higher-order modes also resonate outside the region where the IDT electrode 7 and the pair of reflectors are located. The higher-order modes resonate in the region surrounded by the line connecting the first end La of the first sound velocity adjustment unit L, the second end Lb of the first sound velocity adjustment unit L, the third end Ma of the second sound velocity adjustment unit M, and the fourth end Mb of the second sound velocity adjustment unit M. This region is defined as the higher-order mode resonance region. Even when the first sound velocity adjustment unit L and the second sound velocity adjustment unit M reach the outer side of the pair of reflectors in the x-direction, the higher-order modes resonate in the aforementioned higher-order mode resonance region. Here, when both the first end La and the third end Ma and the second end Lb and the fourth end Mb overlap in the y-direction, the higher-order modes also resonate in the higher-order mode resonance region. In this case, the phases of the higher-order modes become uniform in the higher-order mode resonance region. Therefore, large stray emissions originating from the higher-order modes are generated.

[0058] In contrast, in this embodiment, the first end La and the third end Ma, and the second end Lb and the fourth end Mb do not overlap in the y-direction. This allows for phase shifting of higher-order modes in the higher-order mode resonance region. Consequently, higher-order mode resonance can be suppressed. Therefore, in the elastic wave device 1, not only transverse modes but also higher-order modes can be suppressed.

[0059] Furthermore, it is sufficient that at least one of the two sets of ends, namely the first end La and the third end Ma, and the second end Lb and the fourth end Mb, does not overlap in the y-direction. In this case, both transverse and higher-order modes can be suppressed.

[0060] Here, as Figure 1 As shown, the distance between the first end La and the third end Ma when viewed from the y-direction is defined as B1. Distance B1 is the x-component of the distance between the first end La and the third end Ma. The distance between the second end Lb and the fourth end Mb when viewed from the y-direction is defined as B2. Distance B2 is the x-component of the distance between the second end Lb and the fourth end Mb. Distance B1 is not particularly limited, but is preferably, for example, 1 / 100 or more of the resonant wavelength. Similarly, distance B2 is not particularly limited, but is preferably, for example, 1 / 100 or more of the resonant wavelength. In these cases, in the higher-order mode resonance region, the phase of the higher-order mode can be effectively shifted, and the higher-order mode can be effectively suppressed.

[0061] In this embodiment, when the first end La is located further outward than the first reflector 8 in the x-direction, the upper limit of the distance between the first end La and the first reflector 8 is not particularly limited, but is preferably 1 / 100 or more of the resonant wavelength. Similarly, when the third end Ma is located further outward than the first reflector 8 in the x-direction, the upper limit of the distance between the third end Ma and the first reflector 8 is not particularly limited, but is preferably 1 / 100 or more of the resonant wavelength. In these cases, when the first end La and the third end Ma do not overlap in the y-direction, higher-order modes can be sufficiently suppressed, and the elastic wave device 1 can be miniaturized. Likewise, when the second end Lb is located further outward than the second reflector 9 in the x-direction, the upper limit of the distance between the second end Lb and the second reflector 9 is not particularly limited, but is preferably 1 / 100 or more of the resonant wavelength. When the fourth end Mb is located further outward than the second reflector 9 in the x-direction, the upper limit of the distance between the fourth end Mb and the second reflector 9 is not particularly limited, but is preferably 1 / 100 or more of the resonant wavelength. In these cases, when the second end Lb and the fourth end Mb do not overlap in the y direction, higher-order modes can be sufficiently suppressed, and the elastic wave device 1 can be made smaller.

[0062] The following describes the first to fourth modifications of the first embodiment. In the first to fourth modifications, only the positions of the first sound velocity adjustment unit L and the second sound velocity adjustment unit M differ from those in the first embodiment. In the first to fourth modifications, similar to the first embodiment, transverse modes and higher-order modes can be suppressed.

[0063] exist Figure 6 In the first variation shown, the first end La is located inside the third end Ma in the x-direction. On the other hand, the second end Lb is located outside the fourth end Mb in the x-direction. In addition, in this variation, the first end La, the second end Lb, the third end Ma, and the fourth end Mb are located outside a pair of edge regions in the x-direction.

[0064] In this modified example, the length of the first sound velocity adjustment unit L is the same as the length of the second sound velocity adjustment unit M. However, the lengths of the first sound velocity adjustment unit L and the second sound velocity adjustment unit M may also be different.

[0065] exist Figure 7 In the second variation shown, the first end La is located between the IDT electrode 7 and the first reflector 8. The second end Lb is located between the IDT electrode 7 and the second reflector 9. The third end Ma is located on the electrode finger 18 of the first reflector 8 closest to the IDT electrode 7. The fourth end Mb is located on the electrode finger 19 of the second reflector 9 closest to the IDT electrode 7.

[0066] exist Figure 8In the third variation shown, the first end La and the third end Ma are located on different electrode fingers 18 of the first reflector 8. More specifically, the first end La is provided on the electrode finger 18 closer to the IDT electrode 7, and the third end Ma is provided on the electrode finger 18 farther away from the IDT electrode 7.

[0067] The second end Lb and the fourth end Mb are respectively located on different electrode fingers 19 of the second reflector 9. More specifically, the second end Lb is provided on the electrode finger 19 closer to the IDT electrode 7. The fourth end Mb is provided on the electrode finger 19 farther away from the IDT electrode 7.

[0068] exist Figure 9 In the fourth variation shown, the lengths of the first sound velocity adjustment section L and the second sound velocity adjustment section M are the same. However, the mass-adding membrane 12 and the mass-adding membrane 13 extend obliquely relative to the x-direction. Therefore, the direction in which the first sound velocity adjustment section L extends intersects the x-direction. The direction in which the second sound velocity adjustment section M extends intersects the x-direction. As a result, the first end La and the third end Ma, and the second end Lb and the fourth end Mb do not overlap in the y-direction. Furthermore, in this variation, the first end La, the second end Lb, the third end Ma, and the fourth end Mb are located outside a pair of edge regions in the x-direction.

[0069] Even when the first sound velocity adjustment section L and the second sound velocity adjustment section M extend at an angle relative to the x-direction, the lengths of the first sound velocity adjustment section L and the second sound velocity adjustment section M can still be different.

[0070] Furthermore, in the first embodiment, mass-adding films 12 and 13 are directly disposed on the multiple electrode fingers of the IDT electrode 7, the first reflector 8, and the second reflector 9. This constitutes a pair of sound velocity adjustment units. However, it is not limited to this. Hereinafter, a fifth and sixth modification of the first embodiment are shown, where the position of the mass-adding films differs from that of the first embodiment. Furthermore, in top view, the position of the mass-adding films in the fifth and sixth modifications is the same as that in the first embodiment. In this specification, "top view" refers to a view from... Figure 2 The direction of observation from above. In the fifth and sixth variations, similar to the first embodiment, it is possible to suppress the horizontal mold and higher-order mold.

[0071] exist Figure 10In the fifth modified example shown, mass-added films 12 and 13 are disposed between the plurality of electrode fingers of the IDT electrode 7, the first reflector 8, and the second reflector 9 and the piezoelectric substrate 2. Furthermore, mass-added films 12 and 13 are also disposed on portions between the plurality of electrode fingers on the piezoelectric substrate 2, portions between the IDT electrode 7 and the first reflector 8, and portions between the IDT electrode 7 and the second reflector 9.

[0072] exist Figure 11 In the sixth modified example shown, a protective film 23 is provided on the piezoelectric substrate 2, covering the IDT electrode 7, the first reflector 8, and the second reflector 9. A mass-adding film 12 and a mass-adding film 13 are provided on the protective film 23.

[0073] Return to Figure 2 In the piezoelectric substrate 2 of the first embodiment, a piezoelectric layer 6 is indirectly disposed on the high-velocity acoustic film 4, separated from the low-velocity acoustic film 5. However, the structure of the piezoelectric substrate 2 is not limited to the above structure. Hereinafter, the seventh to ninth modifications of the first embodiment are shown, in which only the structure of the piezoelectric substrate differs from that of the first embodiment. In the seventh to ninth modifications, similar to the first embodiment, transverse modes and higher-order modes can be suppressed. In addition, the energy of the elastic wave can be effectively contained to the piezoelectric layer 6.

[0074] exist Figure 12 In the seventh modified example shown, the piezoelectric substrate 22A has a support substrate 3, a hypersonic film 4, and a piezoelectric layer 6. In this modified example, the piezoelectric layer 6 is directly disposed on the hypersonic film 4, which is a hypersonic material layer.

[0075] exist Figure 13 In the eighth modified example shown, the high-velocity material layer is a high-velocity support substrate 24. The piezoelectric substrate 22B has a high-velocity support substrate 24, a low-velocity film 5, and a piezoelectric layer 6. The low-velocity film 5 is disposed on the high-velocity support substrate 24. The piezoelectric layer 6 is disposed on the low-velocity film 5.

[0076] As the material for the hypersonic support substrate 24, for example, a dielectric material mainly composed of the above materials can be used, such as alumina, silicon carbide, silicon nitride, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, bauxite, zirconium oxide, cordierite, mullite, block talc, forsterite, magnesium oxide, DLC film, or diamond.

[0077] exist Figure 14 In the ninth modified example shown, the piezoelectric substrate 22C has a hypersonic support substrate 24 and a piezoelectric layer 6. In this modified example, the piezoelectric layer 6 is directly disposed on the hypersonic support substrate 24, which is a hypersonic material layer.

[0078] On the other hand, Figure 15 In the 10th variation of the first embodiment shown, the piezoelectric substrate 22D only includes a piezoelectric layer. The piezoelectric substrate 22D is a piezoelectric substrate. In this case, similar to the first embodiment, transverse modes and higher-order modes can be suppressed.

[0079] Figure 16 This is a cross-sectional view showing the elastic wave device according to the second embodiment, through the first extended edge region.

[0080] The difference between this embodiment and the first embodiment is that the piezoelectric substrate 32 has an acoustic reflection film 37. More specifically, the piezoelectric substrate 32 has a support substrate 3, an acoustic reflection film 37, and a piezoelectric layer 6. The acoustic reflection film 37 is disposed on the support substrate 3. The piezoelectric layer 6 is disposed on the acoustic reflection film 37. Apart from the aspects described above, the elastic wave device 31 of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0081] The acoustic reflective membrane 37 is a stack of multiple acoustic impedance layers. More specifically, the acoustic reflective membrane 37 has multiple low acoustic impedance layers and multiple high acoustic impedance layers. The low acoustic impedance layers are layers with relatively low acoustic impedance. The multiple low acoustic impedance layers of the acoustic reflective membrane 37 are low acoustic impedance layer 35a and low acoustic impedance layer 35b. On the other hand, the high acoustic impedance layers are layers with relatively high acoustic impedance. The multiple high acoustic impedance layers of the acoustic reflective membrane 37 are high acoustic impedance layer 34a and high acoustic impedance layer 34b. The low acoustic impedance layers and high acoustic impedance layers are stacked alternately. In addition, the low acoustic impedance layer 35a is the layer located closest to the piezoelectric layer 6 in the acoustic reflective membrane 37.

[0082] Each acoustic reflector 37 has two layers of low acoustic impedance layer and two layers of high acoustic impedance layer. However, it is sufficient for each acoustic reflector 37 to have at least one layer of low acoustic impedance layer and one layer of high acoustic impedance layer.

[0083] Materials used as low acoustic impedance layers include, for example, silicon oxide or aluminum. Materials used as high acoustic impedance layers include, for example, metals such as platinum or tungsten, and dielectrics such as aluminum nitride or silicon nitride.

[0084] The elastic wave device 31 has an acoustic reflective membrane 37, which can effectively confine the energy of the elastic wave to the piezoelectric layer 6.

[0085] The electrode structure on the piezoelectric substrate 32 in this embodiment is the same as in the first embodiment. Therefore, the piston mode is established, and transverse modes can be suppressed. Furthermore, similar to the first embodiment, the phase of higher-order modes in the higher-order mode resonance region can be shifted. Thus, resonance of higher-order modes can be suppressed. Therefore, not only transverse modes but also higher-order modes can be suppressed.

[0086] Figure 17 This is a top view of the elastic wave device according to the third embodiment. Additionally, although in Figure 17 Although no reference numerals are marked in the accompanying drawings, the elastic wave device 41, similar to the first and second embodiments, has a first extended edge region Ex1, a second extended edge region Ex2, and an extended central region Cx, etc.

[0087] In this embodiment, the structure and arrangement of the pair of sound velocity adjustment units differ from those in the first embodiment. Apart from the aspects described above, the elastic wave device 41 of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0088] The multiple electrode fingers of the IDT electrode 47, the first reflector 48, and the second reflector 49 have wide portions. This constitutes a pair of sound velocity adjustment portions. More specifically, the width of the electrode fingers in the wide portions is wider than the width of the electrode fingers in the extended central region Cx. Therefore, the sound velocity in the pair of sound velocity adjustment portions is lower than the sound velocity in the extended central region Cx. The details of the structure of this embodiment will be described below.

[0089] The plurality of electrode fingers of the IDT electrode 47 have wide portions in the first edge region E1 and the second edge region E2. More specifically, the plurality of first electrode fingers 56 have a wide portion 56a in the first edge region E1. Furthermore, the plurality of first electrode fingers 56 have a wide portion 56b in the second edge region E2. Similarly, the plurality of second electrode fingers 57 have a wide portion 57a ​​in the first edge region E1. Furthermore, the plurality of second electrode fingers 57 have a wide portion 57b in the second edge region E2. In this embodiment, all the electrode fingers of the IDT electrode 47 have wide portions. However, electrode fingers having wide portions are not necessarily all the electrode fingers of the IDT electrode 47.

[0090] Here, in the elastic wave device 41, the first end La of the first sound velocity adjustment unit L is located in the x-direction further inward than the third end Ma of the second sound velocity adjustment unit M. The first end La and the third end Ma are disposed on the first reflector 48. More specifically, the plurality of electrode fingers 58 of the first reflector 48 have a wide portion 58a in the first extended edge region Ex1. The first end La of the first sound velocity adjustment unit L is the end of the wide portion 58a furthest from the IDT electrode 47, on the side furthest from the IDT electrode 47. The plurality of electrode fingers 58 of the first reflector 48 have a wide portion 58b in the second extended edge region Ex2. The third end Ma of the second sound velocity adjustment unit M is the end of the wide portion 58b furthest from the IDT electrode 47, on the side furthest from the IDT electrode 47. The electrode finger 58 where the third end Ma is located does not have a wide portion 58a.

[0091] In the elastic wave device 41, starting from the electrode finger 58 closest to the IDT electrode 47 of the first reflector 48, a plurality of electrode fingers 58 consecutively have both a wide width portion 58a and a wide width portion 58b. Electrode fingers 58 farther from the IDT electrode 47 than these plurality of electrode fingers 58 have only the wide width portion 58b of the wide width portion 58a and wide width portion 58b. However, the arrangement of the wide width portions 58a and 58b is not limited to the above-described arrangement. When the third end Ma is located further outward in the x-direction than the first end La, it is sufficient that the wide width portion 58b where the third end Ma is located is located further outward in the x-direction than the wide width portion 58a where the first end La is located. Similarly, when the first end La is located further outward in the x-direction than the third end Ma, it is sufficient that the wide width portion 58a where the first end La is located is located further outward in the x-direction than the wide width portion 58b where the third end Ma is located. It is sufficient that at least one electrode finger 58 has a wide portion 58a, and it is sufficient that at least one electrode finger 58 has a wide portion 58b.

[0092] like Figure 17 As shown, the second end Lb of the first sound velocity adjustment unit L is located in the x-direction inside the fourth end Mb of the second sound velocity adjustment unit M. The second end Lb and the fourth end Mb are disposed on the second reflector 49. More specifically, the plurality of electrode fingers 59 of the second reflector 49 have a wide portion 59a in the first extended edge region Ex1. The second end Lb of the first sound velocity adjustment unit L is the end of the wide portion 59a furthest from the IDT electrode 47, on the side furthest from the IDT electrode 47. The plurality of electrode fingers 59 of the second reflector 49 have a wide portion 59b in the second extended edge region Ex2. The fourth end Mb of the second sound velocity adjustment unit M is the end of the wide portion 59b furthest from the IDT electrode 47, on the side furthest from the IDT electrode 47. The electrode finger 59 on which the fourth end Mb is located does not have a wide portion 59a.

[0093] In the elastic wave device 41, starting from the electrode finger 59 of the second reflector 49 closest to the IDT electrode 47, a plurality of electrode fingers 59 consecutively have both a wide width portion 59a and a wide width portion 59b. Electrode fingers 59 further away from the IDT electrode 47 than these plurality of electrode fingers 59 have only the wide width portion 59b of the wide width portion 59a and wide width portion 59b. However, the arrangement of the wide width portions 59a and 59b is not limited to the above-described arrangement. When the fourth end Mb is located further outward in the x-direction than the second end Lb, it is sufficient that the wide width portion 59b where the fourth end Mb is located is located further outward in the x-direction than the wide width portion 59a where the second end Lb is located. Similarly, when the second end Lb is located further outward in the x-direction than the fourth end Mb, it is sufficient that the wide width portion 59a where the second end Lb is located is located further outward in the x-direction than the wide width portion 59b where the fourth end Mb is located. It is sufficient that at least one electrode finger 59 has a wide portion 59a, and it is sufficient that at least one electrode finger 59 has a wide portion 59b.

[0094] In this embodiment, similar to the first embodiment, the regions in the y-direction are arranged in the order of central region C, a pair of sound velocity adjustment units, and a pair of high-sound velocity regions. This establishes a piston mode, enabling the suppression of transverse modes.

[0095] Furthermore, the first end La and the third end Ma, and the second end Lb and the fourth end Mb do not overlap in the y-direction. This allows for phase shifting of higher-order modes in the higher-order mode resonance region. Therefore, higher-order mode resonance can be suppressed. Thus, not only transverse modes but also higher-order modes can be suppressed.

[0096] Furthermore, when the multiple electrode fingers of the IDT electrode 47, the first reflector 48, and the second reflector 49 have wide portions, a mass-added film can still be provided on the multiple electrode fingers, for example. A pair of sound velocity adjustment units can also be formed by providing the wide portions and the mass-added film.

[0097] Explanation of reference numerals in the attached figures

[0098] 1: Elastic wave device;

[0099] 2: Piezoelectric substrate;

[0100] 3: Support base plate;

[0101] 4: High-speed acoustic membrane;

[0102] 5: Low-velocity membrane;

[0103] 6: Piezoelectric layer;

[0104] 7: IDT electrode;

[0105] 8, 9: First reflector, second reflector;

[0106] 12, 13: Mass-added film;

[0107] 14, 15: Busbar 1 and Busbar 2;

[0108] 16, 17: First electrode finger, second electrode finger;

[0109] 18, 19: Electrode fingers;

[0110] 22A~22D: Piezoelectric substrate;

[0111] 23: Protective film;

[0112] 24: High-speed acoustic support substrate;

[0113] 31: Elastic wave device;

[0114] 32: Piezoelectric substrate;

[0115] 34a, 34b: High acoustic impedance layers;

[0116] 35a, 35b: Low acoustic impedance layers;

[0117] 37: Acoustic reflector membrane;

[0118] 41: Elastic wave device;

[0119] 47: IDT electrode;

[0120] 48, 49: First reflector, second reflector;

[0121] 56, 57: First electrode finger, second electrode finger;

[0122] 56a, 56b, 57a, 57b: Wide section;

[0123] 58, 59: Electrode fingers;

[0124] 58a, 58b, 59a, 59b: Wide section;

[0125] A: Intersection area;

[0126] C: Central Region;

[0127] Cx: Expand the central area;

[0128] E1, E2: First edge region, second edge region;

[0129] Ex1, Ex2: First extended edge region, second extended edge region;

[0130] G1, G2: First interval region, second interval region;

[0131] L, M: First sound velocity adjustment unit, second sound velocity adjustment unit;

[0132] La, Lb: First end, second end;

[0133] Ma, Mb: 3rd end and 4th end.

Claims

1. An elastic wave device, comprising: piezoelectric substrate; An IDT electrode is disposed on the piezoelectric substrate and has multiple electrode fingers; and The first reflector and the second reflector are a pair of reflectors disposed on both sides of the elastic wave propagation direction of the IDT electrode on the piezoelectric substrate. The overlapping portions of adjacent IDT electrodes in the direction of elastic wave propagation constitute the intersection region. The intersection region has: The central region is located on the central side in the direction in which the plurality of electrodes extend; and A pair of edge regions are disposed on either side of the central region in the direction in which the plurality of electrode fingers extend. The region containing the pair of edge regions and overlapping the pair of edge regions in the direction of elastic wave propagation is a pair of extended edge regions. A pair of sound velocity adjustment units are provided in the pair of extended edge regions, and the sound velocity in the pair of sound velocity adjustment units is lower than the sound velocity in the central region. One of the pair of sound velocity adjustment parts has a first end located on the side of the first reflector and a second end located on the side of the second reflector; the other of the pair of sound velocity adjustment parts has a third end located on the side of the first reflector and a fourth end located on the side of the second reflector. The first end, the second end, the third end, and the fourth end are located outside the pair of edge regions in the direction of elastic wave propagation. At least one of the two sets of ends, namely the first end and the third end and the second end and the fourth end, does not overlap in the direction in which the plurality of electrode fingers extend.

2. The elastic wave device according to claim 1, wherein, A pair of high-speed acoustic regions are disposed outside the pair of edge regions along the direction in which the plurality of electrode fingers extend. The speed of sound in the pair of high-speed regions is higher than the speed of sound in the central region.

3. The elastic wave device according to claim 1 or 2, wherein, The first end, the third end, the second end, and the fourth end do not overlap in the direction in which the plurality of electrode fingers extend.

4. The elastic wave device according to claim 1 or 2, wherein, The pair of sound velocity adjustment units reach the outer side of the elastic wave propagation direction of the first reflector and the second reflector.

5. The elastic wave device according to claim 1 or 2, wherein, The direction in which the pair of sound velocity adjustment parts extend is parallel to the direction of elastic wave propagation.

6. The elastic wave device according to claim 1 or 2, wherein, The direction in which the pair of sound velocity adjustment parts extend intersects with the direction of elastic wave propagation.

7. The elastic wave device according to claim 1 or 2, wherein, The pair of sound velocity adjustment units are configured by providing a mass-added membrane.

8. The elastic wave device according to claim 1 or 2, wherein, The region that includes the central region and overlaps with the central region in the direction of elastic wave propagation is the extended central region. The first reflector and the second reflector each have multiple electrode fingers. In the plurality of electrode fingers of the IDT electrode, the plurality of electrode fingers of the first reflector and the plurality of electrode fingers of the second reflector, a wide portion that is wider than the width in the extended central region is provided, thereby constituting the pair of sound velocity adjustment portions.

9. The elastic wave device according to claim 1 or 2, wherein, The piezoelectric substrate has a high-velocity acoustic material layer and a piezoelectric layer disposed directly or indirectly on the high-velocity acoustic material layer. The sound speed of the bulk wave propagating in the high-velocity material layer is higher than the sound speed of the elastic wave propagating in the piezoelectric layer.

10. The elastic wave device according to claim 9, wherein, The piezoelectric substrate has a low-velocity film disposed between the high-velocity material layer and the piezoelectric layer. The sound speed of the bulk wave propagating in the low-velocity membrane is lower than that of the bulk wave propagating in the piezoelectric layer.

11. The elastic wave device according to claim 9, wherein, The hypersonic material layer is a hypersonic support substrate.

12. The elastic wave device according to claim 9, wherein, The piezoelectric substrate has a supporting substrate. The hypersonic material layer is a hypersonic film disposed on the support substrate.

13. The elastic wave device according to claim 1 or 2, wherein, The piezoelectric substrate has an acoustic reflective film and a piezoelectric layer disposed on the acoustic reflective film. The acoustic reflective film has a high acoustic impedance layer with relatively high acoustic impedance and a low acoustic impedance layer with relatively low acoustic impedance. The high acoustic impedance layer and the low acoustic impedance layer are stacked alternately.

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