Elastic wave device

Abstract

To provide an elastic wave device that efficiently utilizes a region on a piezoelectric substrate. [Solution] The elastic wave device 10 comprises a piezoelectric substrate 2 including a piezoelectric layer 6, an IDT electrode 9 provided on the piezoelectric layer 6, a first reflector 7, and a second reflector 8. The shape of the multiple electrode fingers of the IDT electrode 9 in plan view is curved. In each of the first reflector 7 and the second reflector 8, the shape of the multiple reflector electrode fingers in plan view is curved. In the first reflector 7, the pair of reflector busbars are the first reflector busbar 7a and the second reflector busbar 7b, which face each other. In at least a portion of the area of ​​the first reflector 7, the number of multiple reflector electrode fingers increases as you move toward the second reflector busbar 7b side.

Description

[Technical Field]

[0001] This invention relates to an elastic wave apparatus.

[0002] Conventionally, acoustic wave devices have been widely used in applications such as filters for mobile phones. Patent Document 1 below discloses an example of a surface acoustic wave device. In this surface acoustic wave device, a plurality of comb-shaped electrode sections and a pair of reflectors are formed on a piezoelectric substrate. The pair of reflectors are formed on both sides of the plurality of comb-shaped electrode sections in the direction of propagation of the surface acoustic wave. The pair of reflectors are weighted such that the crossing width on the side not facing the comb-shaped electrode section is narrower than the crossing width on the side facing the comb-shaped electrode section. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-005018 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the surface acoustic wave apparatus described in Patent Document 1, the reflector is weighted due to the absence of electrodes on a portion of the piezoelectric substrate. As a result of this weighting, a portion of the piezoelectric substrate does not function as a surface acoustic wave apparatus. Consequently, the area on the piezoelectric substrate cannot be used sufficiently efficiently.

[0005] The object of the present invention is to provide an elastic wave device that can efficiently utilize a region on a piezoelectric substrate. [Means for solving the problem]

[0006] The elastic wave apparatus according to the present invention comprises a piezoelectric substrate including a piezoelectric layer, an IDT electrode provided on the piezoelectric layer having a pair of busbars and a plurality of electrode fingers, and a first reflector and a second reflector provided on the piezoelectric layer so as to face each other with the IDT electrode in between, each having a pair of reflector busbars and a plurality of reflector electrode fingers, wherein the shape of the plurality of electrode fingers of the IDT electrode in plan view is curved, and at any electrode finger among the plurality of electrode fingers, at any portion The excitation direction of the elastic wave is one of the first to third directions, the first direction being perpendicular to the direction in which the electrode finger extends, the second direction being the direction connecting the shortest distance between the electrode finger and the adjacent electrode finger, and the third direction being the direction of the electric field vector generated between the electrode finger and the adjacent electrode finger, and in the first reflector, the pair of reflector busbars being a first reflector busbar and a second reflector busbar facing each other, In each of the first and second reflectors, the shape of the plurality of reflector electrode fingers in plan view is curved, and the plurality of reflector electrode fingers in the first reflector include a first reflector electrode finger whose both ends are directly connected to the first reflector busbar and the second reflector busbar, and a second reflector electrode finger whose one end is not directly connected to the first reflector busbar, the first reflector electrode finger is located on the IDT electrode side than the second reflector electrode finger, all of the second reflector electrode fingers overlap with at least one of the first reflector busbar and the second reflector busbar when viewed from a direction in which the first reflector busbar and the second reflector busbar are facing each other, in at least a portion of the region of the first reflector, the direction of propagation of elastic waves is toward the second reflector busbar, and in that region, the number of the plurality of reflector electrode fingers increases as one moves toward the second reflector busbar. [Effects of the Invention]

[0007] According to the elastic wave apparatus of the present invention, a region on the piezoelectric substrate can be used efficiently.

Brief Description of the Drawings

[0008] [Figure 1] It is a schematic plan view of an elastic wave device according to a first embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view taken along line I-I in FIG. 1. [Figure 3] It is a schematic plan view showing an enlarged view near a first bus bar and a second bus bar of an IDT electrode in the first embodiment of the present invention. [Figure 4] It is a schematic plan view of a first reflector in the first embodiment of the present invention. [Figure 5] It is a schematic plan view of a second reflector in the first embodiment of the present invention. [Figure 6] It is a schematic plan view showing the excitation direction of elastic waves in the first embodiment of the present invention, and the direction in which elastic waves propagate in the first reflector and the second reflector. [Figure 7] It is a schematic plan view of an elastic wave device of a comparative example. [Figure 8] It is a diagram showing impedance frequency characteristics in the first embodiment of the present invention and a comparative example. [Figure 9] It is a diagram showing the relationship between frequency and Q value in the first embodiment of the present invention and a comparative example. [Figure 10] It is a schematic plan view showing a circle including an arc when the shape of electrode fingers of an IDT electrode in the first embodiment of the present invention is approximated to an arc in a plan view. [Figure 11] It is a schematic plan view showing an enlarged view near a first bus bar and a second bus bar of an IDT electrode in a modified example of the first embodiment of the present invention. [Figure 12] It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention. [Figure 13] It is a diagram showing impedance frequency characteristics in the second embodiment of the present invention and a comparative example. [Figure 14] It is a diagram showing the relationship between frequency and Q value in the second embodiment of the present invention and a comparative example. [Figure 15] This is a schematic plan view showing an enlarged view of the area around the first and second busbars of the IDT electrode in a first modified example of a second embodiment of the present invention. [Figure 16] This is a schematic plan view of an elastic wave apparatus according to a second modified example of a second embodiment of the present invention. [Figure 17] Figure 17(a) is a schematic cross-sectional view along the direction of extension of the electrode finger, showing cross-sections of the first electrode finger near the first edge region, the second edge region, and the central region in a third modified example of the second embodiment of the present invention. Figure 17(b) is a schematic cross-sectional view along the direction of extension of the electrode finger, showing cross-sections of the second electrode finger near the first edge region, the second edge region, and the central region in a third modified example of the second embodiment of the present invention. [Figure 18] This is a schematic plan view of an elastic wave apparatus according to a fourth modified example of the second embodiment of the present invention. [Figure 19] This is a schematic plan view of an elastic wave apparatus according to a fifth modified example of the second embodiment of the present invention. [Figure 20] This is a schematic plan view of an elastic wave apparatus according to a third embodiment of the present invention. [Figure 21] This is a schematic plan view of an elastic wave apparatus according to a modified example of the third embodiment of the present invention. [Figure 22] This is a schematic plan view of an elastic wave apparatus according to a fourth embodiment of the present invention. [Figure 23] This is a schematic plan view of an elastic wave apparatus according to a fifth embodiment of the present invention. [Figure 24] This is a schematic front cross-sectional view of an elastic wave apparatus according to a sixth embodiment of the present invention. [Figure 25] This is a schematic front cross-sectional view of an elastic wave apparatus according to a first modification of the sixth embodiment of the present invention. [Figure 26] This is a schematic front cross-sectional view of an elastic wave apparatus according to a second modified example of the sixth embodiment of the present invention. [Figure 27] This is a schematic front cross-sectional view of an elastic wave apparatus according to a seventh embodiment of the present invention. [Figure 28]This is a schematic front cross-sectional view of an elastic wave apparatus according to the eighth embodiment of the present invention. [Figure 29] This is a schematic front cross-sectional view of an elastic wave apparatus according to a first modification of the eighth embodiment of the present invention. [Figure 30] This is a schematic front cross-sectional view of an elastic wave apparatus according to a second modified example of the eighth embodiment of the present invention. [Figure 31] This is a schematic front cross-sectional view of an elastic wave apparatus according to a third modified example of the eighth embodiment of the present invention. [Modes for carrying out the invention]

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

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

[0011] Figure 1 is a schematic plan view of an elastic wave apparatus according to the first embodiment of the present invention. Figure 2 is a schematic cross-sectional view along line II in Figure 1. Note that the dielectric film, which will be described later, is omitted in Figure 1.

[0012] As shown in Figure 1, the elastic wave apparatus 10 has a piezoelectric substrate 2. As shown in Figure 2, the piezoelectric substrate 2 is a laminated substrate including a piezoelectric layer 6. That is, the piezoelectric substrate 2 is a piezoelectric substrate. Specifically, the piezoelectric substrate 2 has a support member 3 and a piezoelectric layer 6. More specifically, the support member 3 has a support substrate 4 and an intermediate layer 5. The intermediate layer 5 includes a first layer 5a and a second layer 5b. The first layer 5a is provided on the support substrate 4. The second layer 5b is provided on the first layer 5a. The piezoelectric layer 6 is provided on the second layer 5b. However, the layer configuration of the piezoelectric substrate 2 is not limited to the above. For example, the intermediate layer 5 may be a single dielectric layer. Alternatively, the piezoelectric substrate 2 may be a substrate consisting only of the piezoelectric layer 6.

[0013] In this embodiment, silicon is used as the material for the support substrate 4. Silicon nitride is used as the material for the first layer 5a. Silicon oxide is used as the material for the second layer 5b. Lithium tantalate with rotational Y-cut X propagation is used as the material for the piezoelectric layer 6. Thus, the piezoelectric layer 6 has a propagation axis. The direction in which the propagation axis extends is the X direction. In this embodiment, the direction in which the propagation axis extends is parallel to the direction in which the dashed line N in Figure 1 extends. Note that the materials of each layer of the piezoelectric substrate 2 are not limited to those described above.

[0014] The piezoelectric layer 6 has a first main surface 6a and a second main surface 6b. The first main surface 6a and the second main surface 6b face each other. Of the two main surfaces 6b, the second main surface 6b is located on the support substrate 4 side. An IDT electrode 9 is provided on the first main surface 6a of the piezoelectric layer 6.

[0015] A dielectric film 18 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 9. Specifically, the dielectric film 18 is provided on the first main surface 6a of the piezoelectric layer 6. Since the IDT electrode 9 is protected by the dielectric film 18, the IDT electrode 9 is less likely to be damaged. In this embodiment, silicon oxide is used as the material for the dielectric film 18. However, the material for the dielectric film 18 is not limited to the above. Note that the dielectric film 18 is not necessarily required.

[0016] As shown in Figure 1, the IDT electrode 9 has a pair of busbars and a plurality of electrode fingers. The pair of busbars are specifically a first busbar 13 and a second busbar 14. The first busbar 13 and the second busbar 14 face each other. The plurality of electrode fingers are specifically a plurality of first electrode fingers 15 and a plurality of second electrode fingers 16. One end of each of the plurality of first electrode fingers 15 is connected to the first busbar 13. One end of each of the plurality of second electrode fingers 16 is connected to the second busbar 14. The plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 are interlocked with each other.

[0017] The shapes of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 in a plan view are curved. In this specification, a plan view means viewing from the direction corresponding to the top in Figure 2. In Figure 2, for example, of the support substrate 4 side and the piezoelectric layer 6 side, the piezoelectric layer 6 side is the top. Furthermore, in this specification, a plan view is synonymous with viewing from the direction opposite the main surfaces. The direction opposite the main surfaces is the direction in which the first main surface 6a and the second main surface 6b of the piezoelectric layer 6 face each other. More specifically, the direction opposite the main surfaces is, for example, the normal direction of the first main surface 6a.

[0018] Figure 3 is a schematic plan view showing an enlarged view of the area around the first and second busbars of the IDT electrode in the first embodiment.

[0019] Each of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 includes a base end, a tip end, and a pair of end edges. Specifically, the base end of the first electrode finger 15 is the portion connected to the first busbar 13. The pair of end edges of the first electrode finger 15 are the portions connecting the base end and the tip end. The tip end of the first electrode finger 15 faces the second busbar 14 across a gap.

[0020] The proximal end of the second electrode finger 16 is the portion connected to the second busbar 14. The pair of end edges of the second electrode finger 16 are the portions connecting the proximal end and the tip. The tip of the second electrode finger 16 faces the first busbar 13 across a gap.

[0021] In the following, the first electrode finger 15 and the second electrode finger 16 may be simply referred to as "electrode finger." The first bus bar 13 and the second bus bar 14 may be simply referred to as "bus bar."

[0022] Returning to Figure 1, a first reflector 7 and a second reflector 8 are provided on the piezoelectric layer 6. The first reflector 7 and the second reflector 8 face each other, sandwiching the IDT electrode 9 in the direction in which the multiple electrode fingers of the IDT electrode 9 are aligned.

[0023] The first reflector 7 and the second reflector 8 each have a pair of reflector busbars and a plurality of reflector electrode fingers. Similar to the plurality of electrode fingers of the IDT electrode 9, the shape of the plurality of reflector electrode fingers of the first reflector 7 and the second reflector 8 in plan view is curved.

[0024] Figure 4 is a schematic plan view of the first reflector in the first embodiment.

[0025] The pair of reflector busbars in the first reflector 7 are the first reflector busbar 7a and the second reflector busbar 7b. The first reflector busbar 7a and the second reflector busbar 7b face each other. The plurality of reflector electrode fingers in the first reflector 7 include a plurality of first reflector electrode fingers 7c and a plurality of second reflector electrode fingers 7d.

[0026] More specifically, one end of each of the multiple first reflector electrode fingers 7c is connected to the first reflector busbar 7a. The other end of each of the multiple first reflector electrode fingers 7c is connected to the second reflector busbar 7b.

[0027] Each of the multiple second reflector electrode fingers 7d is not connected to an electrode. In other words, in this embodiment, each of the multiple second reflector electrode fingers 7d is not connected to the first reflector busbar 7a or to any electrode other than the first reflector busbar 7a. Note that, for the second reflector electrode fingers 7d, it is sufficient that one end is not directly connected to the first reflector busbar 7a. For example, one end of the second reflector electrode finger 7d may be indirectly connected to the first reflector busbar 7a via another electrode.

[0028] The other end of each of the multiple second reflector electrode fingers 7d is connected to the second reflector busbar 7b. However, the other end of each of the multiple second reflector electrode fingers 7d does not have to be directly connected to the second reflector busbar 7b. Alternatively, both ends of the second reflector electrode fingers 7d do not have to be directly connected to the first reflector busbar 7a and the second reflector busbar 7b. In this case, for example, both ends of the second reflector electrode fingers 7d may be indirectly connected to the first reflector busbar 7a and the second reflector busbar 7b via other electrodes.

[0029] The multiple first reflector electrode fingers 7c are located closer to the IDT electrode 9 shown in Figure 1 than the multiple second reflector electrode fingers 7d. Therefore, the multiple first reflector electrode fingers 7c include the reflector electrode finger closest to the IDT electrode 9 and are arranged in order from that reflector electrode finger. On the other hand, the multiple second reflector electrode fingers 7d include the reflector electrode finger furthest from the IDT electrode 9 and are arranged in order from that reflector electrode finger. However, the first reflector 7 only needs to include at least one first reflector electrode finger 7c and at least one second reflector electrode finger 7d.

[0030] When viewed from a direction in which the first reflector busbar 7a and the second reflector busbar 7b are facing each other, all of the second reflector electrode fingers 7d overlap with at least one of the first reflector busbar 7a and the second reflector busbar 7b.

[0031] Figure 5 is a schematic plan view of the second reflector in the first embodiment.

[0032] The pair of reflector busbars in the second reflector 8 are the third reflector busbar 8a and the fourth reflector busbar 8b. The third reflector busbar 8a and the fourth reflector busbar 8b face each other. The plurality of reflector electrode fingers in the second reflector 8 include a plurality of third reflector electrode fingers 8c and a plurality of fourth reflector electrode fingers 8d.

[0033] More specifically, one end of each of the multiple third reflector electrode fingers 8c is connected to the third reflector busbar 8a. The other end of each of the multiple third reflector electrode fingers 8c is connected to the fourth reflector busbar 8b. One end of each of the multiple fourth reflector electrode fingers 8d is connected to the third reflector busbar 8a. The other end of each of the multiple fourth reflector electrode fingers 8d is not connected to an electrode. In other words, in this embodiment, the other end of each of the multiple fourth reflector electrode fingers 8d is not connected to the fourth reflector busbar 8b or to any electrode other than the fourth reflector busbar 8b.

[0034] The multiple third reflector electrode fingers 8c are located closer to the IDT electrode 9 shown in Figure 1 than the multiple fourth reflector electrode fingers 8d. Therefore, the multiple third reflector electrode fingers 8c include the reflector electrode finger closest to the IDT electrode 9 and are arranged in order from that reflector electrode finger. On the other hand, the multiple fourth reflector electrode fingers 8d include the reflector electrode finger furthest from the IDT electrode 9 and are arranged in order from that reflector electrode finger. However, the second reflector 8 only needs to include at least one third reflector electrode finger 8c and at least one fourth reflector electrode finger 8d.

[0035] When viewed from a direction in which the third reflector busbar 8a and the fourth reflector busbar 8b are facing each other, all of the fourth reflector electrode fingers 8d overlap with at least one of the third reflector busbar 8a and the fourth reflector busbar 8b.

[0036] Returning to Figure 1, in this embodiment, the first reflector 7 and the second reflector 8 are configured as described above, which allows the energy of the elastic wave to be suitably confined to the IDT electrode 9 side. Therefore, the region on the piezoelectric substrate 2 can be used efficiently. The details of this will be explained below. In the following, the first reflector electrode finger 7c, the second reflector electrode finger 7d, the third reflector electrode finger 8c, and the fourth reflector electrode finger 8d may be simply referred to as reflector electrode fingers. The first reflector busbar 7a, the second reflector busbar 7b, the third reflector busbar 8a, and the fourth reflector busbar 8b may be simply referred to as reflector busbars.

[0037] The tips of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 each include their tips. The imaginary line formed by connecting the tips of the multiple second electrode fingers 16 is defined as the first envelope E1. Similarly, the imaginary line formed by connecting the tips of the multiple first electrode fingers 15 is defined as the second envelope E2.

[0038] The region between the first envelope E1 and the second envelope E2 is the crossing region A. More specifically, the crossing region A is the region enclosed by the edge of one end of the electrode finger in the direction in which the multiple electrode fingers are aligned, the edge of the other end of the electrode finger, the first envelope E1, and the second envelope E2. Therefore, the first envelope E1 corresponds to the edge of the crossing region A on the first busbar 13 side. The second envelope E2 corresponds to the edge of the crossing region A on the second busbar 14 side. In the crossing region A, adjacent electrode fingers overlap when viewed from the direction in which the first envelope E1 or the second envelope E2 extends.

[0039] In this embodiment, the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends are parallel. However, the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends may intersect.

[0040] In this embodiment, the intersection region A is composed of a single curved region. The curved region is a region in which the shapes of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 in a plan view are curved. One edge of the curved region constituting the intersection region A is the first envelope E1. The other edge is the second envelope E2.

[0041] By applying an AC voltage to the IDT electrode 9, elastic waves are excited in the intersection region A. More specifically, for example, the SH mode is excited as the dominant mode. In this case, Rayleigh waves become unwanted waves. However, the dominant mode is not limited to the SH mode.

[0042] In the intersection region A, the excitation direction of the elastic wave in any portion of any electrode finger among the multiple electrode fingers is one of the following first to third directions. The first direction is perpendicular to the direction in which the electrode finger extends. The second direction is the direction connecting the shortest distance between the electrode finger and the adjacent first electrode finger 15 or second electrode finger 16. The third direction is the direction of the electric field vector generated between the electrode finger and the adjacent first electrode finger 15 or second electrode finger 16. Here, the electric field vector direction is, more specifically, the direction of the electric field vector generated within the piezoelectric layer 6. That is, the third direction is the direction of the electric field vector generated in the piezoelectric layer 6 in the portion that overlaps in a plan view with the portion between the electrode finger and the adjacent first electrode finger 15 or second electrode finger 16.

[0043] Furthermore, since the shape of each electrode finger in the intersection region A is curved, the direction in which a single electrode finger extends differs depending on the position. In this specification, unless otherwise specified, the direction in which the curved electrode fingers extend is as follows.

[0044] First, a pair of edge portions of each electrode finger has a curved shape. When a virtual line parallel to the direction in which the propagation axis extends is drawn so as to connect both edge portions at an arbitrary portion of the electrode finger, the center of gravity of the portion located on the virtual line is defined as the representative point on the virtual line. An infinite number of virtual lines can be drawn on the electrode finger, and there are an infinite number of representative points. The direction in which the tangent of the curve connecting these representative points extends is defined as the direction in which the electrode finger extends.

[0045] Let the angle formed by the excitation direction of the elastic wave and the direction in which the propagation axis of the piezoelectric layer 6 extends be the excitation angle θ. C_prop In the present embodiment, the shape of each electrode finger in a plan view in the crossover region A is a curved shape. Therefore, in the crossover region A, the excitation angle θ C_prop is not uniform. Thus, in the crossover region A, the excitation direction of the elastic wave is not uniform.

[0046] FIG. 6 is a schematic plan view showing the excitation direction of the elastic wave in the first embodiment and the direction in which the elastic wave propagates in the first reflector and the second reflector.

[0047] Let the angle formed by the excitation direction of the elastic wave and the direction in which the propagation axis of the piezoelectric layer 6 extends be the excitation angle θ. C_prop In the present embodiment, the portion through which the second envelope E2 passes is the portion where the excitation angle θ C_prop is 0°. The portions where the excitation angle θ C_prop is 0° are arranged linearly. On the other hand, as shown by the curve M, in the present embodiment, when the portions where the excitation angle θ C_prop is other than 0° and the excitation angles θ C_prop are the same are connected, it becomes a curved shape. In other words, the line connecting the portions where the excitation direction of the elastic wave is the same is the curve M.

[0048] However, the curve M is an example of the portion where the excitation angle θ C_prop is other than 0° and the excitation angles θ C_prop are the same. In the crossover region A, an infinite number of curves similar to the curve M exist. Thus, the shapes of the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 in a plan view are such that the excitation angle θC_prop The shape is defined as having portions that are not 0° and are the same, arranged in a curved pattern.

[0049] In this specification, the excitation angle θ C_prop The positive direction is defined as the counterclockwise direction when viewed from above. In this embodiment, the excitation angle θ is defined in any part of the intersection region. C_prop It is 0° or greater. However, in the present invention, the intersection region is the excitation angle θ C_prop It may include a portion where the value is less than 0°.

[0050] The multiple reflector electrode fingers in the first reflector 7 and the second reflector 8 are shaped to correspond to the multiple electrode fingers of the IDT electrode 9. This allows the first reflector 7 and the second reflector 8 to effectively reflect elastic waves towards the IDT electrode 9.

[0051] In the first reflector 7 and the second reflector 8, more specifically, the shape of the multiple reflector electrode fingers is curved so that in the intersection region A, the portions where the excitation direction of the elastic waves is the same are aligned in the trajectory that is continuous with the trajectory where the propagation direction of the elastic waves is the same.

[0052] For example, if, in the first reflector 7, the portions where the elastic wave propagation direction is the same are aligned in a straight line, then the elastic wave will propagate in the same direction across any adjacent reflector electrode finger. For instance, the elastic wave propagates linearly across any portion of any reflector electrode finger, and after propagating through that portion, it reaches any portion of the adjacent reflector electrode finger. In this case, the propagation direction of the elastic wave is the same across the portions of both reflector electrode fingers through which the elastic wave propagates. Therefore, the propagation direction of the elastic wave does not change for each reflector electrode finger through which the elastic wave propagates. Thus, the propagation direction of the elastic wave is linear.

[0053] On the other hand, in this embodiment, the portions where the propagation direction of the elastic waves is the same are arranged in a curved shape. The direction in which the elastic wave propagates through one reflector electrode finger is linear. For example, the elastic wave propagates linearly through any portion of any reflector electrode finger, and after the elastic wave propagates through that portion, it reaches any portion of the adjacent reflector electrode finger. At this time, the propagation direction of the elastic wave is different between the portions of the elastic wave propagating through both reflector electrode fingers. Therefore, the propagation direction of the elastic wave changes for each reflector electrode finger through which the elastic wave propagates. As a result, the elastic wave propagates through the first reflector 7 in a substantially curved shape, as schematically shown by the curved arrow L1 in Figure 6.

[0054] In this embodiment, the direction of elastic wave propagation is toward the second reflector busbar 7b in all regions of the first reflector 7. However, it is sufficient if the direction of elastic wave propagation is toward the second reflector busbar 7b in at least some regions of the first reflector 7.

[0055] As schematically shown by the curved arrow L2, the elastic wave propagates in a substantially curved manner in the second reflector 8 as well. In this embodiment, in all regions of the second reflector 8, the direction of elastic wave propagation is toward the third reflector busbar 8a. However, in at least some regions of the second reflector 8, the direction of elastic wave propagation may be toward the third reflector busbar 8a. Alternatively, in the present invention, the second reflector 8 does not necessarily have to be configured as described above.

[0056] The features of this embodiment are as follows: 1) The plurality of reflector electrode fingers in the first reflector 7 include the first reflector electrode finger 7c and the second reflector electrode finger 7d. 2) When viewed from a direction in which the first reflector busbar 7a and the second reflector busbar 7b are facing each other, all of the second reflector electrode fingers 7d overlap with at least one of the first reflector busbar 7a and the second reflector busbar 7b. 3) In at least a portion of the region of the first reflector 7, the direction of propagation of elastic waves is toward the second reflector busbar 7b, and in that region, the number of reflector electrode fingers lined up increases toward the second reflector busbar 7b.

[0057] Since the elastic wave device 10 has the configurations described in 1) to 3) above, the energy of the elastic waves can be suitably confined to the IDT electrode 9 side, and the region on the piezoelectric substrate 2 can be used efficiently. Furthermore, when the elastic wave device 10 is used in a filter device, the layout can be easily implemented.

[0058] The details of the above effects will be explained by comparing the first embodiment with the comparative example. In the following, the direction in which the first reflector busbar 7a and the second reflector busbar 7b face each other may be referred to as the first reflector busbar opposing direction. The direction in which the third reflector busbar 8a and the fourth reflector busbar 8b face each other may be referred to as the second reflector busbar opposing direction. In the first embodiment, the first reflector busbar opposing direction and the second reflector busbar opposing direction are directions perpendicular to the direction in which the propagation axis extends.

[0059] The comparative example shown in Figure 7 differs from the first embodiment in that the first reflector 107 does not have a second reflector electrode finger, and the second reflector 108 does not have a fourth reflector electrode finger. Therefore, all reflector electrode fingers of the first reflector 107 are first reflector electrode fingers 7c. One end of each first reflector electrode finger 7c is directly connected to the first reflector busbar 7a. The other end of each first reflector electrode finger 7c is directly connected to the second reflector busbar 7b. Furthermore, the shape of all first reflector electrode fingers 7c in plan view is curved.

[0060] Consequently, in the first reflector 107 of the comparative example, a blank area B is created in the portion that overlaps with the first reflector busbar 7a in the direction opposite to the first reflector busbar. Specifically, blank area B is the area where reflector electrode fingers are not provided. Similarly, in the second reflector 108 of the comparative example, a blank area B is created in the portion that overlaps with the fourth reflector busbar 8b in the direction opposite to the second reflector busbar.

[0061] In the first embodiment and the comparative example, the impedance-frequency characteristics and the relationship between frequency and Q value were derived by simulation.

[0062] Figure 8 shows the impedance frequency characteristics in the first embodiment and comparative example. Figure 9 shows the relationship between frequency and Q value in the first embodiment and comparative example.

[0063] As shown in Figure 8, there is no significant difference between the first embodiment and the comparative example in terms of impedance frequency characteristics. On the other hand, as shown in Figure 9, the maximum value of the Q factor in the first embodiment is larger than that of the comparative example. In other words, in the first embodiment, the energy of the elastic wave can be suitably confined to the IDT electrode 9 side. This is for the following reasons.

[0064] In the first reflector 7 of the first embodiment shown in Figure 6, a plurality of second reflector electrode fingers 7d are provided in the area corresponding to the blank area B in the comparative example shown in Figure 7. As a result, the number of reflector electrode fingers increases as you move toward the second reflector busbar 7b. In the entire region of the first reflector 7, the direction of propagation of elastic waves is toward the second reflector busbar 7b. Therefore, elastic waves propagating from the IDT electrode 9 to the first reflector 7 can be reflected toward the IDT electrode 9 by an even larger number of reflector electrode fingers. Consequently, the Q value of the elastic wave device 10 can be increased.

[0065] In addition, when viewed from the direction opposite the first reflector busbar, all of the second reflector electrode fingers 7d overlap with at least one of the first reflector busbar 7a and the second reflector busbar 7b. This prevents the area of ​​the first reflector 7 from increasing even when multiple second reflector electrode fingers 7d are provided. Therefore, elastic waves can be suitably confined to the IDT electrode 9 side without increasing the size of the first reflector 7, and the Q value of the elastic wave device 10 can be increased. As a result, the region on the piezoelectric substrate 2 can be used efficiently.

[0066] As in the first embodiment, it is preferable that the plurality of reflector electrode fingers in the second reflector 8 include a third reflector electrode finger 8c and a fourth reflector electrode finger 8d. In this case, in the second reflector 8, the fourth reflector electrode finger 8d is provided in the region corresponding to the blank region B in the second reflector 108 of the comparative example shown in Figure 7.

[0067] When viewed from the direction opposite the second reflector busbar, it is preferable that all of the fourth reflector electrode fingers 8d overlap with at least one of the third reflector busbar 8a and the fourth reflector busbar 8b. This prevents the area of ​​the second reflector 8 from increasing even if the fourth reflector electrode fingers 8d are provided.

[0068] In at least a portion of the second reflector 8, the direction of propagation of the elastic wave is toward the third reflector busbar 8a, and it is preferable that the number of reflector electrode fingers lined up in that region increases toward the third reflector busbar 8a. This allows the elastic wave propagating from the IDT electrode 9 to the second reflector 8 to be reflected toward the IDT electrode 9 by an even larger number of reflector electrode fingers. Therefore, the elastic wave can be suitably confined toward the IDT electrode 9 without increasing the size of the second reflector 8, and the Q value of the elastic wave device 10 can be increased.

[0069] As described above, by configuring the first reflector 7 and the second reflector 8 as in the first embodiment, the area on the piezoelectric substrate 2 can be used more efficiently.

[0070] Furthermore, when the elastic wave device 10 is used as an elastic wave resonator in a filter device, the layout is easier to perform. Specifically, for example, the filter device has multiple elastic wave resonators that share the same piezoelectric substrate 2. Because the area of ​​the portion of the piezoelectric substrate 2 where the elastic wave device 10 is placed can be reduced, the degree of freedom in the layout of other elastic wave resonators can be increased. In addition, in the first embodiment, the shape of the portion where the first reflector 7, IDT electrode 9, and second reflector 8 are lined up is close to a rectangle in plan view. Therefore, the layout of the filter device is even easier to perform.

[0071] In the first reflector 7 of the first embodiment, of all reflector electrode fingers, only the plurality of first reflector electrode fingers 7c are connected to the first reflector busbar 7a. On the other hand, of all reflector electrode fingers, the plurality of first reflector electrode fingers 7c and the plurality of second reflector electrode fingers 7d are connected to the second reflector busbar 7b. That is, the number of plurality of reflector electrode fingers connected to the second reflector busbar 7b is greater than the number of plurality of reflector electrode fingers connected to the first reflector busbar 7a. Consequently, the length of the second reflector busbar 7b is longer than the length of the first reflector busbar 7a.

[0072] More specifically, when viewed from the direction opposite the first reflector busbar, the end of the second reflector busbar 7b closer to the IDT electrode 9 does not overlap with the first reflector busbar 7a. However, when viewed from the direction opposite the first reflector busbar, the end of the second reflector busbar 7b further from the IDT electrode 9 overlaps with the first reflector busbar 7a.

[0073] In addition, when viewed from the direction opposite the first reflector busbar, at least a portion of each second reflector electrode finger 7d overlaps with both the first reflector busbar 7a and the second reflector busbar 7b. This reduces the area of ​​the region corresponding to the blank region B shown in Figure 7. Consequently, the area on the piezoelectric substrate 2 can be used more reliably and efficiently.

[0074] Furthermore, in the first reflector 7 of the first embodiment, the line connecting the ends of the multiple second reflector electrode fingers 7d that are not directly connected to the second reflector busbar 7b is a straight line. The angle between the direction in which this straight line extends and the direction in which the first reflector busbar 7a extends is between 45° and 135°. This makes it possible to further reduce the area of ​​the region corresponding to the blank region B shown in Figure 7. Consequently, the area on the piezoelectric substrate 2 can be used more efficiently.

[0075] The same applies to the second reflector 8. Specifically, the length of the third reflector busbar 8a is longer than the length of the fourth reflector busbar 8b. More specifically, when viewed from the direction opposite the second reflector busbar, the end of the third reflector busbar 8a closer to the IDT electrode 9 does not overlap with the fourth reflector busbar 8b. However, when viewed from the direction opposite the second reflector busbar, the end of the third reflector busbar 8a further from the IDT electrode 9 overlaps with the fourth reflector busbar 8b.

[0076] In addition, when viewed from the direction opposite the second reflector busbar, at least a portion of each fourth reflector electrode finger 8d overlaps with both the third reflector busbar 8a and the fourth reflector busbar 8b. This reduces the area of ​​the region corresponding to the blank region B shown in Figure 7. Consequently, the area on the piezoelectric substrate 2 can be used more reliably and efficiently.

[0077] Furthermore, in the second reflector 8, the line connecting the ends of the multiple fourth reflector electrode fingers 8d that are not directly connected to the fourth reflector busbar 8b is a straight line. The angle between the direction in which this straight line extends and the direction in which the third reflector busbar 8a extends is between 45° and 135°. This makes it possible to further reduce the area of ​​the region corresponding to the blank area B shown in Figure 7. Consequently, the area on the piezoelectric substrate 2 can be used more efficiently.

[0078] In the first embodiment, the shape of the multiple electrode fingers in plan view of the IDT electrode 9 is curved. As a result, as described above, in the intersection region A of the first embodiment, the excitation direction and excitation angle θ of the elastic wave are determined. C_prop However, it is not uniform. Specifically, in the intersection region A, the excitation angle θ C_prop The excitation angle θ is not 0°, and C_prop Numerous curved sections with the same excitation angle θ are arranged in the direction in which the first busbar 13 and the second busbar 14 face each other. And between these curved sections, the excitation angle θ C_prop They are different from each other.

[0079] Excitation angle θ C_prop Where the regions differ from each other, the propagation characteristics of unwanted waves differ from each other. This allows for the dispersion of unwanted waves and effective suppression of them. In particular, it is possible to suppress out-of-band unwanted waves such as Rayleigh waves. In this specification, out-of-band in an elastic wave apparatus refers to the region below the resonant frequency of the main mode and the region above the anti-resonant frequency.

[0080] In the first embodiment, the resonant frequency or anti-resonant frequency of the main mode of the elastic wave device 10 substantially coincide in the crossover region A. This allows for effective suppression of unwanted waves and more reliably improves the resonance characteristics.

[0081] More specifically, the excitation angle θ in the intersection region A. C_prop In areas where the resonant frequencies of the main modes and unwanted waves, and the anti-resonant frequencies, are different from each other. Therefore, in each part of the crossover region A, if the resonant frequencies of the main modes or the anti-resonant frequencies are approximately the same, the resonant frequencies of the unwanted waves or the anti-resonant frequencies are different from each other. As a result, the unwanted waves are dispersed. Consequently, unwanted waves can be suppressed.

[0082] In addition, since the resonant frequency or anti-resonant frequency of the main mode in crossover region A are approximately the same, the main mode is optimally excited. Therefore, the resonance characteristics can be improved more reliably.

[0083] In this specification, "approximately matching" means that the absolute value of the difference between the two frequencies is 2% or less of the reference frequency. The reference frequency is the excitation angle θ. C_prop This refers to the frequency when the angle is 0°.

[0084] In crossover region A, it is preferable that the absolute value of the difference between the highest and lowest resonant frequencies of the main mode is 1% or less relative to the reference frequency. Alternatively, in crossover region A, it is preferable that the absolute value of the difference between the highest and lowest anti-resonant frequencies of the main mode is 1% or less relative to the reference frequency. This makes it possible to more reliably improve the resonance characteristics.

[0085] It is preferable that the resonant frequency or anti-resonant frequency of the main mode substantially coincides with at least a portion of the crossover region A, and more preferably substantially coincides with all of it. This allows for more reliable dispersion and suppression of unwanted waves. In addition, it allows for more reliable improvement of the resonance characteristics.

[0086] In the first embodiment, the curved shape of the multiple electrode fingers in the IDT electrode 9 in a plan view, the excitation angle θ in the intersection region A C_prop The excitation angle θ is not 0°, and C_prop Numerous identical curved sections are arranged in a row. The configuration of multiple electrode fingers will be described in more detail below.

[0087] In the IDT electrode 9 shown in Figure 1, the shapes of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 in a plan view are shapes with a gently changing curvature. Specifically, the shapes of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 in a plan view are shapes that can be approximated by circular arcs. However, for example, the shapes of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 in a plan view may be shapes that can be approximated by elliptical arcs. Alternatively, for example, the shape of each electrode finger in a plan view may be a parabola that cannot be approximated by circular arcs or elliptical arcs.

[0088] In the multiple electrode fingers of the first embodiment, the adjacent portion is defined as follows: The adjacent portion of the first electrode finger 15 includes the portion located on the first envelope E1 and is adjacent to the tip of any of the second electrode fingers 16. The adjacent portion of the second electrode finger 16 includes the portion located on the second envelope E2 and is adjacent to the tip of any of the first electrode fingers 15.

[0089] The range of the tip and adjacent portions is based on λ, which is the wavelength defined by the electrode finger pitch. The electrode finger pitch is the distance between the centers of adjacent first electrode finger 15 and second electrode finger 16. When the electrode finger pitch is p, λ = 2p. The tip portion of the electrode finger is defined as the area extending approximately 1λ from the tip of the electrode finger along the direction in which the electrode finger extends. The range of the adjacent portion is also defined as an area extending approximately 1λ along the direction in which the electrode finger extends.

[0090] The electrode finger pitch p that determines the wavelength λ is, for example, the excitation angle θ. C_prop The narrowest electrode finger pitch may be the portion where the angle is 0°. In the first embodiment, the excitation angle θ C_prop The portion where the angle is 0° is the portion on the second envelope E2.

[0091] It is preferable that the shapes of all electrode fingers in the IDT electrode 9 in a plan view are different curve shapes from each other. Three specific examples of this are shown. As the first example, it is preferable that the curvature of all first electrode fingers 15 and all second electrode fingers 16 differs from each other between their tip ends, between adjacent ends, or between their tip ends and adjacent ends, all located on the first envelope E1 side. More specifically, it is preferable that the curvature differs from each other between the tip ends of all second electrode fingers 16, between adjacent ends of all first electrode fingers 15, and between the tip ends of all second electrode fingers 16 and the adjacent ends of all first electrode fingers 15.

[0092] As a second example, it is preferable that the curvature differs between the tips of all first electrode fingers 15 and all second electrode fingers 16 located on the second envelope E2 side, between adjacent tips, or between the tips and adjacent tips. More specifically, it is preferable that the curvature differs between the tips of all first electrode fingers 15, between adjacent tips of all second electrode fingers 16, and between the tips of all first electrode fingers 15 and adjacent tips of all second electrode fingers 16.

[0093] As an example of the third type, the excitation angle θ in all first electrode fingers 15 and all second electrode fingers 16 C_propIt is preferable that the curvature differs between the parts located in the region where the angle is 0°. In this way, by having the shapes of all electrode fingers in the IDT electrode 9 in a plan view being different curve shapes from each other, unwanted waves can be suppressed more reliably and effectively.

[0094] In the first embodiment, all three of the above examples are satisfied. However, in at least one pair of electrode fingers among the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16, the curvature is different between the tip portions located on the first envelope E1 side, between adjacent portions, or between the tip portion and adjacent portions.

[0095] In the first embodiment, the intersection region A is composed of a single curved region. In the first embodiment, in the curved region, the shapes of the multiple electrode fingers in plan view are shapes that can be approximated by circular arcs. In other words, the shapes of the multiple electrode fingers appear to be approximated by circular arcs when viewed from above. In addition, the shapes of the multiple electrode fingers in plan view are different curves from each other. Therefore, the relationship shown in Figure 10 below holds true.

[0096] Figure 10 is a schematic plan view of the IDT electrode in the first embodiment, showing a circle containing an arc when the shape of the electrode finger in a plan view is approximated as a circular arc. In Figure 10, the IDT electrode 9, the first reflector 7, and the second reflector 8 are shown by schematic diagrams with two diagonals added to the contour figures.

[0097] In Figure 10, two circles, R1 and R2, are shown by dashed lines. Circles R1 and R2 are the circles that contain the arcs that approximate the shapes of two different electrode fingers in plan view. The position of the center O1 of circle R1 and the position of the center O2 of circle R2 are different from each other.

[0098] In the curved region, it is preferable that the positions of the centers of the circles containing the arcs, when the plan view shapes of all the first electrode fingers 15 and all the second electrode fingers 16 are approximated as circular arcs, are different from each other. In this case, as described above, the plan view shapes of all the electrode fingers in the IDT electrode 9 are different curved shapes from each other.

[0099] In the first embodiment, when the shape of all first electrode fingers 15 and all second electrode fingers 16 in plan view is approximated as an arc, the positions of the centers of the circles containing the arcs are different from each other. Furthermore, each reflector electrode finger in the first reflector 7 and the second reflector 8 has the same shape as each electrode finger in the IDT electrode 9. Specifically, in each of the first reflector 7 and the second reflector 8, when the shape of all reflector electrode fingers in plan view is approximated as an arc, the positions of the centers of the circles containing the arcs are different from each other.

[0100] Thus, the shapes of the multiple reflector electrode fingers in the first reflector 7 and the second reflector 8 correspond to the shapes of the multiple electrode fingers in the IDT electrode 9. As a result, the first reflector 7 and the second reflector 8 can effectively reflect elastic waves towards the IDT electrode 9.

[0101] However, in the curved region, it is sufficient that the positions of the centers of the circles containing the arcs when the shape of at least one pair of electrode fingers from among the plurality of first electrode fingers 15 and plurality of second electrode fingers 16 of the IDT electrode 9 in a plan view is approximated as an arc. In each of the first reflector 7 and the second reflector 8, it is sufficient that the positions of the centers of the circles containing the arcs when the shape of at least one pair of reflector electrode fingers in a plan view is approximated as an arc.

[0102] Furthermore, in the curved region, the planar shapes of the multiple first electrode fingers 15 and multiple second electrode fingers 16 of the IDT electrode 9 can be approximated as elliptical arcs. In this case, in the curved region, when the planar shapes of all the first electrode fingers 15 and all the second electrode fingers 16 of the IDT electrode 9 are approximated as elliptical arcs, it is preferable that the positions of the centroids of the ellipses containing the elliptical arcs are different from each other. Here, the centroid refers to the centers of the two foci of the ellipse. And, in each of the first reflector 7 and the second reflector 8, when the planar shapes of all the reflector electrode fingers are approximated as elliptical arcs, it is preferable that the positions of the centroids of the ellipses containing the elliptical arcs are different from each other.

[0103] However, in the curved region, when the shape of at least one pair of electrode fingers from among the multiple first electrode fingers 15 and multiple second electrode fingers 16 of the IDT electrode 9 in a plan view is approximated as an elliptical arc, it is sufficient that the positions of the centroids of the ellipses containing the elliptical arcs are different from each other. In this case, in each of the first reflector 7 and the second reflector 8, when the shape of at least one pair of reflector electrode fingers from among the multiple reflector electrode fingers in a plan view is approximated as an elliptical arc, it is sufficient that the positions of the centroids of the ellipses containing the elliptical arcs are different from each other.

[0104] The reference line is defined as a line extending parallel to the direction in which the propagation axis extends, and the angle between the reference line and the first envelope E1 is defined as the intersection angle θ. C1_AP The angle between the baseline and the second envelope E2 is the intersection angle θ. C2_AP In the first embodiment, the intersection angle θ C1_AP and intersection angle θ C2_AP All of these are 0°. However, the intersection angle θ C1_AP and intersection angle θ C2_AP It is not limited to 0°.

[0105] In the first embodiment, in the intersection region A, the duty cycle is equal to the excitation angle θ. C_prop It changes accordingly. As a result, the resonant frequencies are approximately matched throughout the entire crossover region A. However, this is not the only way.

[0106] For example, at least one of the duty cycle, electrode finger pitch, and the thickness of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 is the excitation angle θ C_prop It is preferable that these parameters change accordingly. At least one of these parameters is such that the resonant frequency or anti-resonant frequency of the main mode substantially coincides in at least a portion of the crossover region A, according to the excitation angle θ. C_prop It is preferable that these parameters change accordingly. At least one of these parameters should be such that the resonant frequency or anti-resonant frequency of the main mode substantially coincides with the excitation angle θ in all of the crossover region A. C_prop It is more preferable that it changes accordingly. In these cases, the resonance characteristics of the elastic wave apparatus 10 can be more reliably improved.

[0107] Alternatively, if the thickness of the intermediate layer 5 within the piezoelectric substrate 2 affects the frequency, the excitation angle θ in the crossover region A is adjusted accordingly. C_prop This may be changed accordingly. In the first embodiment, when a dielectric film 18 is provided on the piezoelectric substrate 2 so as to cover the IDT electrode 9, the thickness of the dielectric film 18 is changed in the intersection region A, according to the excitation angle θ. C_prop The parameters may be changed accordingly. The parameters of the IDT electrode 9, or multiple parameters other than those of the IDT electrode 9, are set in the crossover region A, and the excitation angle θ C_prop This may be varied accordingly. In these cases as well, the resonant frequency or anti-resonant frequency of the main mode can be made to substantially match in at least a part or all of the crossover region A.

[0108] Excitation angle θ of IDT electrode 9 C_prop In the portion where the same, it is preferable that at least one of the electrode finger pitch and duty cycle is constant. Excitation angle θ C_prop In the portion where the same parameters are present, it is more preferable that both the electrode finger pitch and the duty cycle remain constant. This makes it possible to more reliably improve the resonance characteristics of the elastic wave device 10.

[0109] In the first embodiment, the configuration of a pair of busbars in the IDT electrode 9 effectively confines the energy of the elastic wave to the crossover region A. This is described in detail below.

[0110] As shown in Figure 1, the first busbar 13 is provided with a plurality of openings 13d. More specifically, the first busbar 13 has a first inner busbar portion 13a and a first outer busbar portion 13b, and a plurality of first connecting portions 13c. The first inner busbar portion 13a and the first outer busbar portion 13b face each other. Of the first inner busbar portion 13a and the first outer busbar portion 13b, the first inner busbar portion 13a is located on the side of intersection region A. The plurality of first connecting portions 13c connect the first inner busbar portion 13a and the first outer busbar portion 13b. Each of the plurality of openings 13d is an opening surrounded by the first inner busbar portion 13a, the first outer busbar portion 13b, and the plurality of first connecting portions 13c.

[0111] Similarly, the second busbar 14 also has a second inner busbar portion 14a, a second outer busbar portion 14b, and a plurality of second connecting portions 14c. The second busbar 14 is provided with a plurality of openings 14d.

[0112] The first inner busbar portion 13a extends parallel to the first envelope E1. As shown in Figure 3, the first inner busbar portion 13a faces the plurality of second electrode fingers 16 with a gap between them. The second inner busbar portion 14a extends parallel to the second envelope E2. The second inner busbar portion 14a faces the plurality of first electrode fingers 15 with a gap between them.

[0113] In this embodiment, each of the multiple first connection portions 13c of the first bus bar 13 extends along the extension of the first electrode finger 15. The multiple first connection portions 13c are not provided along the extension of the second electrode finger 16. On the other hand, in the intersection region A, the first electrode finger 15 and the second electrode finger 16 are arranged alternately. Therefore, the speed of sound in the region of the first bus bar 13 where the multiple openings 13d are formed is higher than the speed of sound in the intersection region A. As a result, a high-speed region is formed in the region of the first bus bar 13 where the multiple openings 13d are formed. The high-speed region is a region where the speed of sound is higher than the speed of sound in the region located towards the center of the intersection region A.

[0114] More specifically, as shown in Figure 3, the intersection region A has a central region F and a pair of edge regions. The pair of edge regions are specifically the first edge region H1 and the second edge region H2. The first edge region H1 includes the first envelope E1 as its edge. The second edge region H2 includes the second envelope E2 as its edge. The first edge region H1 and the second edge region H2 face each other with the central region F in between. The above high-sound-velocity region is the region where the speed of sound is higher than the speed of sound in the central region F.

[0115] The first edge region H1 is defined as the region where the tip of the second electrode finger 16 and the adjacent portion of the first electrode finger 15 are located. That is, the first edge region H1 is defined as a region of approximately 1λ from the tip of the second electrode finger 16 along the direction in which the second electrode finger 16 extends, with the second electrode finger 16 as the reference. Similarly, the second edge region H2 is defined as a region of approximately 1λ from the tip of the first electrode finger 15 along the direction in which the first electrode finger 15 extends, with the first electrode finger 15 as the reference.

[0116] Similar to the region in the first bus bar 13 where multiple openings 13d are provided, a high-sound-velocity region is also formed in the region in the second bus bar 14 where multiple openings 14d are provided.

[0117] Here, energy leakage of the elastic wave can occur due to the conversion of the dominant mode. For example, if the SH wave is used as the dominant mode of the elastic wave, energy leakage occurs when the SH wave is converted to a Rayleigh wave, or from an SH wave to a bulk wave. Such leakage occurs from the crossover region A towards the busbar side.

[0118] In the first embodiment, the first inner busbar portion 13a faces the plurality of second electrode fingers 16 with a gap between them. This suppresses the leakage of elastic wave energy associated with mode conversion. Furthermore, the second inner busbar portion 14a faces the plurality of first electrode fingers 15 with a gap between them. This also suppresses the leakage of elastic wave energy associated with mode conversion.

[0119] The distance between the first inner busbar portion 13a and the second electrode finger 16 is preferably 0.5λ or less. Similarly, the distance between the second inner busbar portion 14a and the first electrode finger 15 is preferably 0.5λ or less. This effectively suppresses the leakage of elastic wave energy associated with mode conversion.

[0120] In addition, a high-sound-velocity region is formed between the first inner busbar section 13a and the first outer busbar section 13b. This allows the energy of the elastic waves to be effectively confined to the intersection region A. Similarly, a high-sound-velocity region is formed between the second inner busbar section 14a and the second outer busbar section 14b. This allows the energy of the elastic waves to be effectively confined to the intersection region A.

[0121] As shown in Figure 1, the first reflector busbar 7a of the first reflector 7 and the third reflector busbar 8a of the second reflector 8 are each provided with multiple openings, similar to the first busbar 13. The second reflector busbar 7b of the first reflector 7 and the fourth reflector busbar 8b of the second reflector 8 are each provided with multiple openings, similar to the second busbar 14. However, each reflector busbar of each reflector does not necessarily have to be provided with an opening.

[0122] Incidentally, in the IDT electrode 9 of the first embodiment, the shape of the multiple electrode fingers in plan view is a shape that can be approximated as an arc. The shape of the multiple electrode fingers in plan view may, for example, include the shape of an arc. In this case, the shape of each of the multiple electrode fingers in plan view includes a shape corresponding to each arc in a plurality of concentric circles. Therefore, the centers of the circles containing the arcs in the shapes of the multiple electrode fingers coincide. This center is defined as a fixed point.

[0123] As described above, in the first embodiment, the excitation angle θ C_prop The parts that are the same are arranged in a curved shape. On the other hand, if the shape of multiple electrode fingers in a plan view is an arc shape, the excitation angle θ C_prop The parts where the same values ​​are aligned in a straight line. Specifically, along the straight line passing through the above fixed point and intersection region, the excitation angle θ C_prop The parts that are the same are lined up.

[0124] Alternatively, the shape of the multiple electrode fingers in plan view may include, for example, the shape of an elliptical arc. In this case, the shape of each of the multiple electrode fingers in plan view includes the shape corresponding to the respective elliptical arc in multiple ellipses whose centroids are at the same position. When the centroid is taken as a fixed point, the excitation angle θ is on the straight line passing through the fixed point and the intersection region. C_prop The parts that are the same are lined up.

[0125] It is preferable that the shapes of the multiple reflector electrode fingers of the first and second reflectors correspond to the shapes of the multiple electrode fingers of the IDT electrode. Specifically, if the shape of the multiple electrode fingers in a plan view includes an arc shape, it is preferable that the shape of the multiple reflector electrode fingers in a plan view also includes an arc shape. It is preferable that the centers of the circles containing the arcs in the shapes of the multiple electrode fingers and the multiple reflector electrode fingers coincide. If the shape of the multiple electrode fingers in a plan view includes an elliptical arc shape, it is preferable that the shape of the multiple reflector electrode fingers in a plan view also includes an elliptical arc shape. It is preferable that the centroids of the ellipses containing the elliptical arcs in the shapes of the multiple electrode fingers and the multiple reflector electrode fingers coincide. As a result, the first and second reflectors can effectively reflect elastic waves towards the IDT electrode.

[0126] As shown in Figure 1, each busbar of the IDT electrode 9 is provided with multiple openings. However, each busbar of the IDT electrode 9 does not necessarily have to have an opening. In addition, each busbar may be provided with multiple offset electrodes. For example, in the modified example of the first embodiment shown in Figure 11, the IDT electrode 9A has multiple offset electrodes. Specifically, the multiple offset electrodes of the IDT electrode 9A are multiple first offset electrodes 11 and multiple second offset electrodes 12. One end of each of the multiple first offset electrodes 11 is connected to the first busbar 13A. The first electrode fingers 15 and the first offset electrodes 11 are arranged alternately. Note that the first busbar 13A does not have an opening.

[0127] One end of each of the multiple second offset electrodes 12 is connected to the second busbar 14A. The second electrode fingers 16 and the second offset electrodes 12 are arranged alternately. The second busbar 14A does not have any openings.

[0128] Similar to the multiple first electrode fingers 15 and the multiple second electrode fingers 16, the multiple first offset electrodes 11 and the multiple second offset electrodes 12 each include a base end and a tip end. The base ends of the first electrode fingers 15 and the first offset electrodes 11 are the parts connected to the first busbar 13A. The base ends of the second electrode fingers 16 and the second offset electrodes 12 are the parts connected to the second busbar 14A. The tip end of the first electrode finger 15 and the tip end of the second offset electrode 12 face each other with a gap between them. The tip end of the second electrode finger 16 and the tip end of the first offset electrode 11 face each other with a gap between them.

[0129] In this modified example, the plan view shapes of the multiple first offset electrodes 11 are curved. Specifically, the shape of each first offset electrode 11 corresponds to the shape of the opposing second electrode finger 16. More specifically, the plan view shapes of the multiple first offset electrodes 11 are shapes that can be approximated by circular arcs. Furthermore, when the plan view shapes of any first offset electrode 11 and the second electrode finger 16 facing the first offset electrode 11 are approximated by circular arcs, the circle containing each arc is the same circle.

[0130] The curvature of the tips of all the first offset electrodes 11 are different from each other. This makes it possible to at least bring the conditions of the crossover region A where the main mode is excited closer to, or even match, the conditions of the region where the multiple first offset electrodes 11 are provided. This allows the main mode to be effectively reflected towards the crossover region A. However, for example, the curvature of the tips of at least one pair of the multiple first offset electrodes 11 may be different from each other. In this case as well, the main mode can still be effectively reflected towards the crossover region A.

[0131] In the intersection region A, even if the plan view shapes of multiple electrode fingers can be approximated as elliptical arcs, it is preferable that the plan view shapes of the multiple first offset electrodes 11 are curved and that the curvature is not constant for each first offset electrode 11. It is preferable that the plan view shapes of the multiple first offset electrodes 11 are shapes that can be approximated as elliptical arcs. Furthermore, it is preferable that the ellipse containing each elliptical arc when the plan view shapes of any first offset electrode 11 and the second electrode finger 16 facing the first offset electrode 11 are approximated as elliptical arcs is the same ellipse.

[0132] It is preferable that the curvature of the tip portions of at least one pair of first offset electrodes 11 among the plurality of first offset electrodes 11 are different from each other, and it is more preferable that the curvature of the tip portions of all first offset electrodes 11 are different from each other. This allows the dominant mode to be effectively reflected to the crossing region A.

[0133] Alternatively, for example, the shape of the multiple first offset electrodes 11 in plan view may be linear. In this case, the distance from the tip of the first offset electrode 11 to the first busbar 13A can be shortened. This makes it possible to lower the electrical resistance of the IDT electrode 9A. Therefore, when an elastic wave device is used as a filter device, it is possible to suppress an increase in insertion loss.

[0134] In this modified example, the shape of the multiple second offset electrodes 12 in plan view is linear. As a result, the shape of each second offset electrode 12 corresponds to the shape of the opposing first electrode finger 15. Therefore, the dominant mode can be effectively reflected to the crossing region A. In addition, the electrical resistance of the IDT electrode 9A can be reduced.

[0135] Furthermore, in this modified example, similar to the first embodiment, the region on the piezoelectric substrate 2 can be used efficiently.

[0136] Furthermore, it is sufficient that at least the first busbar 13A of the two busbars 14A is provided with multiple offset electrodes. In other words, it is sufficient that at least multiple first offset electrodes 11 are provided among multiple first offset electrodes 11 and multiple second offset electrodes 12. This allows for the reflection of the main mode to the crossover region A, thereby suppressing leakage of the main mode.

[0137] Alternatively, in the present invention, each busbar of the IDT electrode may not have multiple openings, nor may it have multiple offset electrodes.

[0138] Returning to Figure 2, the following shows examples of materials for each component in the piezoelectric substrate 2.

[0139] As the material for the support substrate 4, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; semiconductors such as silicon; or materials mainly composed of the above materials can be used. The spinel mentioned above includes aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of the spinel mentioned above include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4. It is preferable that high-resistivity silicon is used for the support substrate 4. It is desirable that the volume resistivity of the material for the support substrate 4 be 1000 Ω·cm or more. In the first embodiment, high-resistivity silicon is used as the material for the support substrate 4.

[0140] The first layer 5a of the intermediate layer 5 is a high-speed film. A high-speed film is a film with a relatively high sound velocity. More specifically, the speed of sound of bulk waves propagating through a high-speed film is higher than the speed of sound of elastic waves propagating through the piezoelectric layer 6. As the material for the first layer 5a, which is a high-speed film, it is possible to use piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; semiconductors such as silicon; or materials mainly composed of the above materials. Note that the spinel mentioned above contains an aluminum compound containing one or more elements selected from Mg, Fe, Zn, Mn, etc., and oxygen. Examples of spinels mentioned above include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4. In the first embodiment, silicon nitride is used as the material for the first layer 5a.

[0141] The second layer 5b of the intermediate layer 5 is a low-sound-velocity film. A low-sound-velocity film is a film with a relatively low sound velocity. More specifically, the speed of sound of bulk waves propagating through the low-sound-velocity film is lower than the speed of sound of bulk waves propagating through the piezoelectric layer 6. As the material for the second layer 5b, which is a low-sound-velocity film, for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds of silicon oxide to which fluorine, carbon, or boron have been added, or materials mainly composed of the above materials can be used. In the first embodiment, silicon oxide is used as the material for the second layer 5b.

[0142] As the material for the piezoelectric layer 6 shown in Figure 2, for example, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate) can be used. It is preferable that lithium tantalate or lithium niobate is used as the material for the piezoelectric layer 6. In the first embodiment, lithium tantalate is used as the material for the piezoelectric layer 6.

[0143] In the first embodiment, the piezoelectric substrate 2 is laminated in the following order: a first layer 5a as a high-sonic-velocity film, a second layer 5b as a low-sonic-velocity film, and a piezoelectric layer 6. This allows the energy of elastic waves to be effectively confined to the piezoelectric layer 6.

[0144] The materials for the IDT electrode 9, the first reflector 7, and the second reflector 8 may be one or more metals selected from the group consisting of Ti, Mo, Ru, W, Al, Pt, Ir, Cu, Cr, and Sc. The IDT electrode 9, the first reflector 7, and the second reflector 8 may consist of a single layer metal film or a multilayer metal film. In the first embodiment, Al is used as the material for the IDT electrode 9, the first reflector 7, and the second reflector 8.

[0145] In this specification, the main component refers to a component that accounts for more than 50% by weight. The main component material may exist in one of the following states: single crystal, polycrystalline, or amorphous, or in a mixture thereof.

[0146] In the first embodiment, the number of reflector electrode fingers in the first reflector 7 is the same as the number of reflector electrode fingers in the second reflector 8. However, the number of reflector electrode fingers in the first reflector 7 and the number of reflector electrode fingers in the second reflector 8 may be different. This example is shown in the second embodiment.

[0147] Figure 12 is a schematic plan view of an elastic wave apparatus according to the second embodiment.

[0148] This embodiment differs from the first embodiment in that the number of reflector electrode fingers in the first reflector 27 is less than the number of reflector electrode fingers in the second reflector 8. Apart from the above, the elastic wave apparatus of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment.

[0149] An elastic wave apparatus having the configuration of the second embodiment and an elastic wave apparatus having the configuration of the comparative example shown in Figure 7 were prepared, and the impedance frequency characteristics and the relationship between frequency and Q value were compared. The design parameters of the elastic wave apparatus having the configuration of the second embodiment were as follows. Here, the IB gap is defined as the dimension of the gap between the tip of the electrode finger and the busbar along the direction in which the electrode finger extends. In the second embodiment, the IB gap between the tip of the second electrode finger 16 and the first busbar 13, and the IB gap between the tip of the first electrode finger 15 and the second busbar 14 are the same. In the following design parameters, the logarithm of the reflector electrode fingers is the logarithm of reflector electrode fingers that overlap in the direction in which the propagation axis extends. The logarithm of reflector electrode fingers that overlap in the direction in which the propagation axis extends differs depending on the position. Therefore, the logarithm has a maximum and a minimum value.

[0150] Support substrate: Material...Si, plane orientation...(111), ψ in Euler angles (φ,θ,ψ)...73° Intermediate layer, first layer: Material...SiN, Thickness...300nm Second layer of the intermediate layer: Material...SiO2, Thickness...300nm Piezoelectric layer: Material... LiTaO3 with rotational Y-cut 55° X propagation, thickness... 400 nm IDT electrode: Material...Al, Thickness...100nm Dielectric film: Material...SiO2, Thickness...30nm Excitation angle θ C_prop Maximum value: 15.9° Crossing angle θ C1_AP :0° Crossing angle θ C2_AP :0° Wavelength λ: Excitation angle θ C_prop 2.09 μm in the region where the angle is 0° Number of electrode fingers in IDT electrodes: 151 pairs Duty cycle: Excitation angle θ C_prop 0.5 IB gap: 0.27 μm Number of reflector electrode fingers in the first reflector: 9 pairs or more, 15 pairs or less Number of reflector electrode fingers in the second reflector: 15 pairs or more, 20 pairs or less

[0151] The design parameters in the comparative example were the same as those in the first embodiment, except that the number of logarithmic pairs of reflector electrode fingers in the second reflector was set to 15 pairs.

[0152] Figure 13 shows the impedance-frequency characteristics in the second embodiment and comparative example. Figure 14 shows the relationship between frequency and Q value in the second embodiment and comparative example.

[0153] As shown in Figure 13, there is no significant difference in impedance frequency characteristics between the second embodiment and the comparative example. On the other hand, as shown in Figure 14, the maximum value of the Q factor is larger in the second embodiment than in the comparative example. As in the second embodiment shown in Figure 12, the Q factor can be increased even when the number of reflector electrode fingers in the first reflector 27 and the number of reflector electrode fingers in the second reflector 8 are different.

[0154] In addition, in the second embodiment, as in the first embodiment, the area of ​​the region corresponding to the blank region B shown in Figure 7 can be reduced. Therefore, without increasing the size of the first reflector 27 and the second reflector 8, the elastic waves can be suitably confined to the IDT electrode 9 side, and the Q value of the elastic wave device can be increased. As a result, the region on the piezoelectric substrate 2 can be used efficiently.

[0155] In the present invention, a configuration utilizing a piston mode can also be used. An example of this is shown by the first to third modifications of the second embodiment. In the first to third modifications, as in the second embodiment, the region on the piezoelectric substrate 2 can be used efficiently.

[0156] Figure 15 is a schematic plan view showing an enlarged view of the area around the first and second busbars of the IDT electrode in the first modified example of the second embodiment.

[0157] Each electrode finger of the IDT electrode 29A has a wide portion in the first edge region H1 and the second edge region H2. The width of the electrode finger in the wide portion is wider than the width of the electrode finger in the central region F.

[0158] Specifically, the first electrode finger 25A has a wide portion 25a in the first edge region H1. The second electrode finger 26A also has a wide portion 26a in the first edge region H1. On the other hand, the first electrode finger 25A has a wide portion 25b in the second edge region H2. The second electrode finger 26A also has a wide portion 26b in the second edge region H2. As a result, the speed of sound in the first edge region H1 and the second edge region H2 is lower than the speed of sound in the central region F. This constitutes a low-speed region in the first edge region H1 and the second edge region H2. A low-speed region is a region where the speed of sound is lower than the speed of sound in the central region F.

[0159] In this modified example, the central region F and a pair of low-sonic regions are arranged in this order from the inside to the outside in the direction in which the first busbar 13 and the second busbar 14 face each other. This establishes a piston mode. This allows for the suppression of unwanted transverse modes. In addition, the energy of the main mode can be effectively confined to the central side of the crossover region A, thereby improving the characteristics of the main mode.

[0160] The configuration of the IDT electrode 29A is the same as in the second embodiment, except for the first edge region H1 and the second edge region H2.

[0161] Furthermore, it is sufficient that at least one electrode finger has a wide portion in at least one of the first edge region H1 and the second edge region H2. However, it is preferable that multiple electrode fingers have wide portions in at least one of the first edge region H1 and the second edge region H2, and more preferably that all electrode fingers have wide portions. Moreover, it is even more preferable that multiple electrode fingers have wide portions in both the first edge region H1 and the second edge region H2, and even more preferable that all electrode fingers have wide portions. This makes it possible to more reliably establish the piston mode.

[0162] The shape of the multiple electrode fingers of the IDT electrode 29A in a plan view is a shape that can be approximated as an arc. However, the configuration in which a low-sonic region is provided in the first edge region H1 or the second edge region H2 can also be adopted in other configurations of the present invention in which the shape of the electrode fingers differs from that of this modified example.

[0163] In the IDT electrode 29A, the width of each electrode finger is widened across the entire edge region. The shape of each widened portion in plan view is rectangular. However, each electrode finger may be widened in at least a portion of each edge region. The shape of each widened portion in plan view is not limited to a rectangle.

[0164] Although not shown in the diagram, each reflector electrode finger of the first and second reflectors also has a widened portion in the region where each edge region extends in the direction in which the edge region extends. That is, in each reflector electrode finger, the width of the portion located in that region is wider than the width of other portions. Note that each reflector electrode finger does not necessarily have to have a widened portion.

[0165] In the second modified example shown in Figure 16, a pair of mass-adding films 21 are provided, thereby creating low-sonic regions in the first edge region H1 and the second edge region H2, respectively. Specifically, one of the pair of mass-adding films 21 is provided in the first edge region H1, and the other of the pair of mass-adding films 21 is provided in the second edge region H2. In this modified example, the configuration of the IDT electrode 9 is the same as in the second embodiment.

[0166] Each mass-adding film 21 has a strip-like shape. Each pair of mass-adding films 21 is continuously provided across multiple electrode fingers on the IDT electrode 9. Therefore, each mass-adding film 21 is also provided in the areas between the electrode fingers on the piezoelectric substrate 2. A suitable dielectric material can be used for the mass-adding film 21.

[0167] Furthermore, the mass-adding film 21 only needs to be laminated with at least one of the plurality of electrode fingers in at least one of the first edge region H1 and the second edge region H2. Specifically, the mass-adding film 21 only needs to be provided so that, when viewed from above, it overlaps with at least one of the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 in at least one of the first edge region H1 and the second edge region H2. In this case, a low-sonic region is formed in at least a part of at least one of the first edge region H1 and the second edge region H2.

[0168] It is preferable that in at least one of the first edge region H1 and the second edge region H2, a plurality of electrode fingers are laminated with the mass-adding film 21, and it is more preferable that all electrode fingers are laminated with the mass-adding film 21. Furthermore, it is more preferable that in both the first edge region H1 and the second edge region H2, a plurality of electrode fingers are laminated with the mass-adding film 21, and it is even more preferable that all electrode fingers are laminated with the mass-adding film 21. This makes it possible to more reliably establish the piston mode.

[0169] In the portion where the electrode fingers and mass-adding film 21 are laminated, they are laminated in the order of piezoelectric substrate 2, electrode fingers, and mass-adding film 21. However, in the portion where the electrode fingers and mass-adding film 21 are laminated, they may be laminated in the order of piezoelectric substrate 2, mass-adding film 21, and electrode fingers. That is, the mass-adding film 21 may be provided between the piezoelectric substrate 2 and the electrode fingers.

[0170] When the dielectric film 18 shown in Figure 2 is provided, the dielectric film 18 may cover the mass-adding film 21, or the mass-adding film 21 may be provided on the dielectric film 18. When the mass-adding film 21 is provided on the dielectric film 18, an appropriate metal or dielectric material can be used for the mass-adding film 21.

[0171] In this modified example, the mass-adding film 21 is also provided in the region extending in the direction in which each edge region extends. Therefore, the portions of each reflector electrode finger of the first reflector 27 and the second reflector 8 that are located in the respective regions are also laminated with the mass-adding film 21. Note that each reflector electrode finger does not necessarily have to be laminated with the mass-adding film 21.

[0172] In this modified example, one mass-adding film 21 is provided in each edge region. However, multiple mass-adding films 21 may be provided in each edge region. For example, in the first edge region H1, a mass-adding film 21 may be provided on each first electrode finger 15 and each second electrode finger 16. More specifically, the mass-adding film 21 may be provided on only one electrode finger. The same applies to the second edge region H2. In this case, an appropriate metal or dielectric material can be used as the material for the mass-adding film 21.

[0173] For example, if each mass-adding film 21 is provided on only one electrode finger, the material of the mass-adding film 21 may be the same metal used for each electrode finger. This configuration corresponds to the third modified configuration shown in Figures 17(a) and 17(b). That is, as shown in Figure 17(a), in the IDT electrode 29C, the thickness of the first edge region H1 and the second edge region H2 of the first electrode finger 25C is greater than the thickness of the central region F of the first electrode finger 25C. As shown in Figure 17(b), the thickness of the first edge region H1 and the second edge region H2 of the second electrode finger 26C is greater than the thickness of the central region F of the second electrode finger 26C. As a result, low-sonic regions are formed in the first edge region H1 and the second edge region H2, respectively.

[0174] Figure 17(a) schematically shows a cross-section of the first electrode finger 25C along the direction in which the first electrode finger 25C extends. Similarly, Figure 17(b) schematically shows a cross-section of the second electrode finger 26C along the direction in which the second electrode finger 26C extends. The configuration of the IDT electrode 29C is the same as in the second embodiment, except for the first edge region H1 and the second edge region H2.

[0175] It is sufficient that the thickness of at least one electrode finger in at least one of the first edge region H1 and the second edge region H2 is greater than the thickness of the electrode finger in the central region F. However, it is preferable that the thickness of multiple electrode fingers in at least one of the first edge region H1 and the second edge region H2 is greater than the thickness of the electrode finger in the central region F. It is even more preferable that the thickness of all electrode fingers in at least one of the first edge region H1 and the second edge region H2 is greater than the thickness of the electrode finger in the central region F.

[0176] Furthermore, it is more preferable that the thickness of the multiple electrode fingers in both the first edge region H1 and the second edge region H2 is greater than the thickness of the electrode fingers in the central region F. It is even more preferable that the thickness of all the electrode fingers in both the first edge region H1 and the second edge region H2 is greater than the thickness of the electrode fingers in the central region F. This makes it possible to more reliably establish the piston mode.

[0177] In this modified example, the thickness of each electrode finger is increased throughout the entire edge region. However, each electrode finger may be increased in thickness in at least a portion of each edge region.

[0178] Although not shown in the diagram, in each reflector electrode finger of the first and second reflectors, the thickness of the portion located in the region extending in the direction in which each edge region extends is greater than the thickness of the other portions. However, the thickness of each reflector electrode finger does not necessarily have to be greater in each edge region.

[0179] The low-sonic region may be provided by at least one of the first to third modified configurations. For example, the low-sonic region may be provided by multiple configurations from the first to third modified configurations.

[0180] Returning to Figure 12, in the second embodiment, one end of the second reflector electrode finger 7d is not connected to the electrode. However, this one end may be connected to the electrode.

[0181] For example, in the fourth modified example of the second embodiment shown in Figure 18, the first reflector 27D has an end connection electrode 27e. The end connection electrode 27e is connected to both the first reflector busbar 7a and the second reflector busbar 7b. One end of each of the multiple second reflector electrode fingers 7d is directly connected to the end connection electrode 27e. As a result, one end of each second reflector electrode finger 7d is indirectly connected to the first reflector busbar 7a via the end connection electrode 27e. The other end of each of the multiple second reflector electrode fingers 7d is directly connected to the second reflector busbar 7b.

[0182] In this modified example, the second reflector 28D also has an end connection electrode 28e. The end connection electrode 28e is connected to both the third reflector busbar 8a and the fourth reflector busbar 8b. One end of each of the multiple fourth reflector electrode fingers 8d is directly connected to the third reflector busbar 8a. The other end of each fourth reflector electrode finger 8d is directly connected to the end connection electrode 28e. As a result, the other end of each fourth reflector electrode finger 8d is indirectly connected to the fourth reflector busbar 8b via the end connection electrode 28e.

[0183] In this modified example, as in the second embodiment, the region on the piezoelectric substrate 2 can be used efficiently. In addition, in the first reflector 27D, the end connection electrode 27e can short-circuit a plurality of second reflector electrode fingers 7d. In the second reflector 28D, the end connection electrode 28e can short-circuit a plurality of fourth reflector electrode fingers 8d.

[0184] The end connection electrodes 27e and 28e have a linear shape in plan view. More specifically, in the first reflector 27D, the angle between the direction in which the end connection electrode 27e extends and the direction in which the first reflector busbar 7a extends is between 45° and 135°. This makes it possible to further reduce the area of ​​the region corresponding to the blank area B shown in Figure 7. Therefore, the area on the piezoelectric substrate 2 can be used more efficiently.

[0185] Similarly, in the second reflector 28D, the angle between the direction in which the end connection electrode 28e extends and the direction in which the third reflector busbar 8a extends is between 45° and 135°. This makes it possible to further reduce the area of ​​the region corresponding to the blank area B shown in Figure 7. Therefore, the area on the piezoelectric substrate 2 can be used more efficiently. However, the shape of the end connection electrodes 27e and 28e in plan view may be curved.

[0186] The first reflector in the present invention may include at least one second reflector electrode finger. If the second reflector includes a fourth reflector electrode finger, the second reflector may include at least one fourth reflector electrode finger.

[0187] For example, in the first reflector 27D in this modified example, one end of at least one second reflector electrode finger 7d is indirectly connected to the first reflector busbar 7a via an end connection electrode 27e. The other end of the second reflector electrode finger 7d is directly connected to the second reflector busbar 7b. In the second reflector 28D, one end of at least one fourth reflector electrode finger 8d is directly connected to the third reflector busbar 8a. The other end of the fourth reflector electrode finger 8d is indirectly connected to the fourth reflector busbar 8b via an end connection electrode 28e.

[0188] In this modified example, a pair of mass-adding films 21 are provided, similar to the second modified example. However, the mass-adding films 21 are not required.

[0189] In the second embodiment shown in Figure 12, the second reflector 8 includes a plurality of fourth reflector electrode fingers 8d. However, the second reflector 8 does not necessarily have to include the fourth reflector electrode fingers 8d.

[0190] For example, in the fifth modification of the second embodiment shown in Figure 19, the second reflector 28E does not include a fourth reflector electrode finger. The plurality of reflector electrode fingers of the second reflector 28E includes only a plurality of third reflector electrode fingers 8c. One end of each of the plurality of third reflector electrode fingers 8c is directly connected to a third reflector busbar 8a, and the other end of each is directly connected to a fourth reflector busbar 8b.

[0191] In this modified example, the elastic waves can be suitably confined to the IDT electrode 9 side without increasing the size of the first reflector 27, and the Q value of the elastic wave device can be increased. Therefore, the region on the piezoelectric substrate 2 can be used efficiently.

[0192] Returning to Figure 12, in the second embodiment, when viewed from the direction opposite the first reflector busbar, at least a portion of each second reflector electrode finger 7d overlaps with both the first reflector busbar 7a and the second reflector busbar 7b. However, when viewed from the direction opposite the first reflector busbar, it is sufficient that all second reflector electrode fingers 7d overlap with at least one of the first reflector busbar 7a and the second reflector busbar 7b.

[0193] Figure 20 is a schematic plan view of an elastic wave apparatus according to the third embodiment.

[0194] This embodiment differs from the first embodiment in the configuration of the first reflector 37 and the second reflector 38. The number of reflector electrode fingers in the first reflector 37 is the same as the number of reflector electrode fingers in the second reflector 38. Except for the above, the elastic wave apparatus of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment.

[0195] The first reflector 37 has an end connection electrode 37e. In plan view, the end connection electrode 37e has a curved shape. Specifically, the end connection electrode 37e is connected to both the first reflector busbar 7a and the second reflector busbar 7b. The end connection electrode 37e extends toward the IDT electrode 9 side as it moves from the second reflector busbar 7b side toward the first reflector busbar 7a side. One end of each of the multiple second reflector electrode fingers 7d is directly connected to the end connection electrode 37e. Thus, one end of each second reflector electrode finger 7d is indirectly connected to the first reflector busbar 7a via the end connection electrode 37e. The other end of each of the multiple second reflector electrode fingers 7d is directly connected to the second reflector busbar 7b.

[0196] In the first reflector 37, the length of the second reflector busbar 7b is longer than the length of the first reflector busbar 7a. More specifically, when viewed from the direction opposite the first reflector busbar, neither the end of the second reflector busbar 7b closer to the IDT electrode 9 nor the end of the second reflector busbar 7b further away from the IDT electrode 9 overlaps with the first reflector busbar 7a.

[0197] In addition, when viewed from the direction opposite the first reflector busbar, some of the second reflector electrode fingers 7d do not overlap with the first reflector busbar 7a.

[0198] On the other hand, when viewed from the direction opposite the first reflector busbar, all parts of all second reflector electrode fingers 7d overlap with the second reflector busbar 7b. This prevents the area of ​​the first reflector 37 from becoming larger, even if multiple second reflector electrode fingers 7d are provided.

[0199] Furthermore, in the entire region of the first reflector 37, the direction of elastic wave propagation is toward the second reflector busbar 7b, and in this region, the number of reflector electrode fingers increases as one moves toward the second reflector busbar 7b. As a result, the first reflector 37 can suitably confine the elastic waves toward the IDT electrode 9, thereby increasing the Q value of the elastic wave device. Thus, the region on the piezoelectric substrate 2 can be used efficiently.

[0200] In this embodiment, the second reflector 38 also has an end connection electrode 38e. The shape of the end connection electrode 38e in plan view is curved. Specifically, the end connection electrode 38e is connected to both the third reflector busbar 8a and the fourth reflector busbar 8b. The end connection electrode 38e extends toward the IDT electrode 9 side as it moves from the third reflector busbar 8a side toward the fourth reflector busbar 8b side. One end of each of the multiple fourth reflector electrode fingers 8d is directly connected to the third reflector busbar 8a, and the other end of each is directly connected to the end connection electrode 38e. As a result, the other end of each fourth reflector electrode finger 8d is indirectly connected to the fourth reflector busbar 8b via the end connection electrode 38e.

[0201] In the second reflector 38, the length of the third reflector busbar 8a is longer than the length of the fourth reflector busbar 8b. More specifically, when viewed from the direction opposite the second reflector busbar, neither the end of the third reflector busbar 8a closer to the IDT electrode 9 nor the end of the third reflector busbar 8a further away from the IDT electrode 9 overlaps with the fourth reflector busbar 8b.

[0202] In addition, when viewed from the direction opposite the second reflector busbar, some of the fourth reflector electrode fingers 8d do not overlap with the fourth reflector busbar 8b.

[0203] On the other hand, when viewed from the direction opposite the second reflector busbar, all parts of all fourth reflector electrode fingers 8d overlap with the third reflector busbar 8a. This prevents the area of ​​the second reflector 38 from increasing even if multiple fourth reflector electrode fingers 8d are provided.

[0204] Furthermore, in the entire region of the second reflector 38, the direction of propagation of elastic waves is toward the third reflector busbar 8a, and in this region, the number of reflector electrode fingers increases as you move toward the third reflector busbar 8a. As a result, the second reflector 38 can suitably confine the elastic waves toward the IDT electrode 9, thereby increasing the Q value of the elastic wave device.

[0205] The first reflector 37 and the second reflector 38 have the above configuration, which allows for more efficient use of the area on the piezoelectric substrate 2. Note that the multiple reflector electrode fingers of the second reflector 38 do not necessarily have to include the fourth reflector electrode finger 8d.

[0206] For example, in the modified example of the third embodiment shown in Figure 21, the first reflector 37 is configured in the same way as in the third embodiment. On the other hand, the second reflector 28E does not include a fourth reflector electrode finger. The plurality of reflector electrode fingers of the second reflector 28E include only a plurality of third reflector electrode fingers 8c. One end of each of the plurality of third reflector electrode fingers 8c is directly connected to the third reflector busbar 8a, and the other end of each is directly connected to the fourth reflector busbar 8b.

[0207] In this modified example, the elastic waves can be suitably confined to the IDT electrode 9 side without increasing the size of the first reflector 37, and the Q value of the elastic wave device can be increased. Therefore, the region on the piezoelectric substrate 2 can be used efficiently.

[0208] In the first to third embodiments and each of the modified examples, the shape of the multiple electrode fingers of the IDT electrode in plan view is convex toward the second reflector side and convex toward the first busbar side. The shape of the multiple reflector electrode fingers in the first and second reflectors in plan view is also a shape that corresponds to the shape of the multiple electrode fingers in plan view.

[0209] Specifically, the shape of the multiple reflector electrode fingers of the first reflector in a plan view is convex on the side approaching the IDT electrode and convex on the side facing the first reflector busbar. The shape of the multiple reflector electrode fingers of the second reflector in a plan view is convex on the side moving away from the IDT electrode and convex on the side facing the third reflector busbar.

[0210] Due to the shapes of the multiple electrode fingers in the IDT electrode and the multiple reflector electrode fingers in the first and second reflectors, the direction of elastic wave propagation in the first and second reflectors is, for example, the direction indicated by the curved arrows L1 and L2 in Figure 6. More specifically, in the entire region of the first reflector, the direction of elastic wave propagation is toward the second reflector busbar. In the entire region of the second reflector, the direction of elastic wave propagation is toward the third reflector busbar.

[0211] However, the first reflector may include a region where the direction of propagation of elastic waves is toward the first reflector busbar. On the other hand, the second reflector may include a region where the direction of propagation of elastic waves is toward the fourth reflector busbar. This example is shown by the fourth embodiment.

[0212] Figure 22 is a schematic plan view of the elastic wave apparatus according to the fourth embodiment.

[0213] This embodiment differs from the first embodiment in the shape of the IDT electrode 49, the first reflector 47, and the second reflector 48. This embodiment also differs from the first embodiment in that the first reflector 47 has an end connection electrode 27e, and the second reflector 48 has an end connection electrode 28e. Apart from the above, the elastic wave apparatus 40 of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment.

[0214] The dashed line N in Figure 22 extends parallel to the direction in which the propagation axis extends. The dashed line N passes through the center of the intersection region A. The region on the first busbar 13 side of the dashed line N is configured in the same way as in the first embodiment. Therefore, in the region on the first busbar 13 side of the dashed line N, the plan view shapes of the plurality of first electrode fingers 45 and plurality of second electrode fingers 46 are convex toward the second reflector 48 side and convex toward the first busbar 13 side. On the other hand, in the region of the IDT electrode 49 on the second busbar 14 side of the dashed line N, the plan view shapes of the plurality of first electrode fingers 45 and plurality of second electrode fingers 46 are convex toward the second reflector 48 side and convex toward the second busbar 14 side.

[0215] The first reflector 47 and the second reflector 48 each have two regions separated by a dashed-dot line N. Hereafter, the dashed-dot line N may be referred to as the boundary line. In the region of the first reflector 47 on the side of the boundary line to the first reflector busbar 7a, the shape of the multiple reflector electrode fingers in a plan view is convex towards the IDT electrode 49 and also convex towards the first reflector busbar 7a. In the region of the first reflector 47 on the side of the boundary line to the second reflector busbar 7b, the shape of the multiple reflector electrode fingers in a plan view is convex towards the IDT electrode 49 and also convex towards the second reflector busbar 7b.

[0216] In the first reflector 47, one end of each of the multiple first reflector electrode fingers 47c is connected to the first reflector busbar 7a. The other end of each of the multiple first reflector electrode fingers 47c is connected to the second reflector busbar 7b.

[0217] The end connection electrode 27e of the first reflector 47 is connected to both the first reflector busbar 7a and the second reflector busbar 7b. The shape of the end connection electrode 27e in plan view is linear. The ends of each of the multiple second reflector electrode fingers 47d are directly connected to the end connection electrode 27e. As a result, both ends of each second reflector electrode finger 47d are indirectly connected to the first reflector busbar 7a and the second reflector busbar 7b via the end connection electrode 27e. In other words, one end of each second reflector electrode finger 47d is indirectly connected to the first reflector busbar 7a via the end connection electrode 27e. The other end of each second reflector electrode finger 47d is indirectly connected to the second reflector busbar 7b via the end connection electrode 27e.

[0218] In this embodiment, when viewed from the direction opposite the first reflector busbar, all portions of all second reflector electrode fingers 47d overlap with both the first reflector busbar 7a and the second reflector busbar 7b. In a portion of the first reflector 47, the direction of elastic wave propagation is toward the second reflector busbar 7b, and in that portion, the number of reflector electrode fingers lined up increases toward the second reflector busbar 7b. In addition, in another portion of the first reflector 47, the direction of elastic wave propagation is toward the first reflector busbar 7a, and in that portion, the number of reflector electrode fingers lined up increases toward the first reflector busbar 7a.

[0219] In this embodiment, the above configuration allows for the elastic waves to be suitably confined to the IDT electrode 49 side without increasing the size of the first reflector 47, thereby increasing the Q value of the elastic wave device 40. Consequently, the region on the piezoelectric substrate 2 can be used efficiently.

[0220] In the second reflector 48, one end of each of the multiple third reflector electrode fingers 48c is connected to the third reflector busbar 8a. The other end of each of the multiple third reflector electrode fingers 48c is connected to the fourth reflector busbar 8b.

[0221] The end connection electrode 28e of the second reflector 48 is connected to both the third reflector busbar 8a and the fourth reflector busbar 8b. The shape of the end connection electrode 28e in plan view is linear. In the region of the second reflector 48 on the side of the dashed line N, which serves as a boundary line, to the third reflector busbar 8a, one end of each of the multiple fourth reflector electrode fingers 48d is directly connected to the third reflector busbar 8a. The other end of each of the multiple fourth reflector electrode fingers 48d is directly connected to the end connection electrode 28e. Thus, the other end of each fourth reflector electrode finger 48d is indirectly connected to the fourth reflector busbar 8b via the end connection electrode 28e.

[0222] In the region of the second reflector 48 on the side of the boundary line to the fourth reflector busbar 8b, one end of each of the multiple fourth reflector electrode fingers 48d is directly connected to the end connection electrode 28e. Thus, one end of each fourth reflector electrode finger 48d is indirectly connected to the third reflector busbar 8a via the end connection electrode 28e. The other end of each of the multiple fourth reflector electrode fingers 48d is directly connected to the fourth reflector busbar 8b.

[0223] In this embodiment, when viewed from the direction opposite the second reflector busbar, all parts of all fourth reflector electrode fingers 48d overlap with both the third reflector busbar 8a and the fourth reflector busbar 8b. In a portion of the second reflector 48, the direction of elastic wave propagation is toward the third reflector busbar 8a, and in this portion, the number of reflector electrode fingers increases as one moves toward the third reflector busbar 8a. In addition, in another portion of the second reflector 48, the direction of elastic wave propagation is toward the fourth reflector busbar 8b, and in this portion, the number of reflector electrode fingers increases as one moves toward the fourth reflector busbar 8b. As a result, the elastic waves can be suitably confined to the IDT electrode 49 side without increasing the size of the second reflector 48, and the Q value of the elastic wave device 40 can be increased.

[0224] The first reflector 47 and the second reflector 48 have the above configuration, which allows for more efficient use of the area on the piezoelectric substrate 2.

[0225] In the first reflector 47, it is sufficient that one end of at least one second reflector electrode finger 47d is indirectly connected to the first reflector busbar 7a via the end connection electrode 27e. The other end of the second reflector electrode finger 47d is indirectly connected to the second reflector busbar 7b via the end connection electrode 27e.

[0226] In the second reflector 48, in some areas, one end of at least one fourth reflector electrode finger 48d may be directly connected to the third reflector busbar 8a. The other end of the fourth reflector electrode finger 48d may be indirectly connected to the fourth reflector busbar 8b via the end connection electrode 28e. In the second reflector 48, in other areas, one end of at least one second reflector electrode finger 48d may be indirectly connected to the third reflector busbar 8a via the end connection electrode 28e. The other end of the second reflector electrode finger 48d may be directly connected to the fourth reflector busbar 8b.

[0227] The shapes of the multiple electrode fingers of the IDT electrode 49, and the multiple reflector electrode fingers of the first reflector 47 and the second reflector 48, in plan view are shapes that can be approximated as circular arcs. Each electrode finger of the IDT electrode 49, and each reflector electrode finger of the first reflector 47 and the second reflector 48, have a portion located in one of two regions bounded by the dashed line N, and a portion located in the other region.

[0228] Furthermore, for any electrode finger of the IDT electrode 49, the shape of the portion located in one region and the shape of the portion located in the other region in a plan view are shapes that can be approximated by the same circular arc. Similarly, for any reflector electrode finger of the first reflector 47 and the second reflector 48, the shape of the portion located in one region and the shape of the portion located in the other region in a plan view are shapes that can be approximated by the same circular arc.

[0229] However, the shape of each electrode finger of the IDT electrode 49, and the shape of each reflector electrode finger of the first reflector 47 and the second reflector 48 in a plan view are not limited to those described above. The shape of each electrode finger and each reflector electrode finger in a plan view may be, for example, a shape that can be approximated by an elliptical arc, a shape that is a parabola that cannot be approximated by a circular arc or an elliptical arc, a shape that is a circular arc, or a shape that is an elliptical arc.

[0230] In this embodiment, in the intersection region A, the shapes of the multiple electrode fingers in a plan view are each approximated by a single circular arc. In this case, there is only one curved region in the intersection region A. This is also true in the first to third embodiments and their respective modifications. However, the intersection region A may include multiple curved regions. This example is shown in the fifth embodiment.

[0231] Figure 23 is a schematic plan view of the elastic wave apparatus according to the fifth embodiment.

[0232] This embodiment differs from the first embodiment in that the intersection region A includes multiple curved regions. More specifically, the multiple curved regions in this embodiment are the first curved region W1 and the second curved region W2. The shapes of the multiple reflector electrode fingers of the first reflector 57 and the second reflector 58 correspond to the shapes of the multiple electrode fingers of the IDT electrode 59. Except for the above, the elastic wave device 50 of this embodiment has the same configuration as the elastic wave device 10 of the first embodiment.

[0233] In the elastic wave apparatus 50, the shapes of the plurality of first electrode fingers 55 and the plurality of second electrode fingers 56 in plan view each have an inflection point. In this specification, an inflection point is a point where different curves are connected, or where a curve and a straight line are connected. When different curves are connected at an inflection point, the directions of the curved shapes are different with the inflection point as the boundary. The difference in the directions of the curved shapes means, for example, that the curvature directions of the curved shapes are different. The curvature direction here refers to the direction in which the curve bends so as to be convex toward the first reflector 57, or the direction in which it bends so as to be convex toward the second reflector 58. In this embodiment, the two curved shapes are inverted toward each other with the inflection point as the boundary.

[0234] Specifically, the plan view shapes of the multiple first electrode fingers 55 and the multiple second electrode fingers 56 each include two parts that can be approximated as arcs. Furthermore, the plan view shape of each electrode finger includes a shape where these two parts are connected. The center of the circle containing one of the arcs and the center of the circle containing the other arc face each other, with the IDT electrode 59 in between. In the plan view shape of each electrode finger, the point where the two parts are connected is the inflection point.

[0235] One edge of the first curved region W1 is the first envelope E1. The other edge of the first curved region W1 is the boundary between the first curved region W1 and the second curved region W2. One edge of the second curved region W2 is the second envelope E2. The other edge of the second curved region W2 is the boundary between the first curved region W1 and the second curved region W2. In each curved region, the planar shapes of the plurality of first electrode fingers 55 and the plurality of second electrode fingers 56 are each approximated by a single circular arc. The boundary between the first curved region W1 and the second curved region W2 passes through the inflection point of each electrode finger.

[0236] In this embodiment, the boundary between the first curved region W1 and the second curved region W2 is located in the area through which the dashed line N in Figure 23 passes. In other words, the inflection points of the multiple electrode fingers on the IDT electrode 59 are aligned on the dashed line N. The dashed line N extends parallel to the direction in which the propagation axis extends and passes through the center of the intersection region A. However, the boundary between the curved regions may extend at an angle with respect to the propagation axis.

[0237] As shown in Figure 23, the multiple reflector electrode fingers in the first reflector 57 and the second reflector 58 each have an inflection point. The two curved shapes are inverted relative to each other, with the inflection point as the boundary. The direction of curvature here refers to the direction in which the curve becomes convex towards the IDT electrode 59, or the direction in which it becomes convex away from the IDT electrode 59. The inflection points of the multiple reflector electrode fingers in the first reflector 57 and the second reflector 58 are aligned on the dashed line N. The first reflector 57 and the second reflector 58 each have two regions with the dashed line N as the boundary. Hereafter, the dashed line N may be referred to as the boundary line.

[0238] In the region of the first reflector 57 on the side of the boundary line to the first reflector busbar 7a, the shape of the multiple reflector electrode fingers in a plan view is convex toward the side approaching the IDT electrode 59 and convex toward the first reflector busbar 7a. In the region of the first reflector 57 on the side of the boundary line to the second reflector busbar 7b, the shape of the multiple reflector electrode fingers in a plan view is convex toward the side away from the IDT electrode 59 and convex toward the second reflector busbar 7b.

[0239] In the first reflector 57, one end of each of the multiple first reflector electrode fingers 57c is connected to the first reflector busbar 7a. The other end of each of the multiple first reflector electrode fingers 57c is connected to the second reflector busbar 7b.

[0240] The first reflector 57 has an end connection electrode 57e. The end connection electrode 57e is connected to both the first reflector busbar 7a and the second reflector busbar 7b. In plan view, the shape of the end connection electrode 57e is a combination of straight lines and curves. Specifically, the straight portion of the end connection electrode 57e is located in the region on the first reflector busbar 7a side of the boundary line. The curved portion of the end connection electrode 57e is located in the region on the second reflector busbar 7b side of the boundary line.

[0241] Each of the multiple second reflector electrode fingers 57d is directly connected to an end connection electrode 57e. This means that each of the two second reflector electrode fingers 57d is indirectly connected to the first reflector busbar 7a via the end connection electrode 57e. The other end of each of the multiple second reflector electrode fingers 57d is directly connected to the second reflector busbar 7b.

[0242] In the region of the first reflector 57 on the side of the boundary line to the second reflector busbar 7b, the shape of the end connection electrode 57e in plan view is the same as the shape of the multiple first reflector electrode fingers 57c and the multiple second reflector electrode fingers 57d in plan view. Therefore, in this region, the end connection electrode 57e performs the function of reflecting elastic waves, similar to the multiple reflector electrode fingers.

[0243] In this embodiment, when viewed from the direction opposite the first reflector busbar, all of the second reflector electrode fingers 57d overlap with at least the first reflector busbar 7a. In the region of the first reflector 57 on the side of the boundary line to the first reflector busbar 7a, the direction of propagation of elastic waves is toward the second reflector busbar 7b, and in this region, the number of reflector electrode fingers increases as one moves toward the second reflector busbar 7b. As a result, elastic waves can be suitably confined to the IDT electrode 59 side without increasing the size of the first reflector 57, and the Q value of the elastic wave device 50 can be increased. Therefore, the region on the piezoelectric substrate 2 can be used efficiently.

[0244] Furthermore, in the region of the first reflector 57 on the side of the boundary line to the second reflector busbar 7b, the direction of propagation of elastic waves is toward the second reflector busbar 7b, and the number of reflector electrode fingers lined up is constant. However, as described above, the configuration in the region of the first reflector 57 on the side of the boundary line to the first reflector busbar 7a suppresses the enlargement of the first reflector 57 and provides the effect of suitably confining elastic waves to the IDT electrode 59.

[0245] In the region of the second reflector 58 on the third reflector busbar 8a side of the boundary line, the shape of the multiple reflector electrode fingers in a plan view is convex toward the side away from the IDT electrode 59 and convex toward the third reflector busbar 8a. In the region of the second reflector 58 on the fourth reflector busbar 8b side of the boundary line, the shape of the multiple reflector electrode fingers in a plan view is convex toward the side approaching the IDT electrode 59 and convex toward the fourth reflector busbar 8b.

[0246] In the second reflector 58, one end of each of the multiple third reflector electrode fingers 58c is connected to the third reflector busbar 8a. The other end of each of the multiple third reflector electrode fingers 58c is connected to the fourth reflector busbar 8b.

[0247] The second reflector 58 has an end connection electrode 58e. The end connection electrode 58e is connected to both the third reflector busbar 8a and the fourth reflector busbar 8b. In plan view, the shape of the end connection electrode 58e is a combination of straight lines and curves. Specifically, the straight portion of the end connection electrode 58e is located in the area on the fourth reflector busbar 8b side of the boundary line. The curved portion of the end connection electrode 58e is located in the area on the third reflector busbar 8a side of the boundary line.

[0248] One end of each of the multiple fourth reflector electrode fingers 58d is directly connected to the third reflector busbar 8a. The other end of each of the multiple fourth reflector electrode fingers 58d is directly connected to the end connection electrode 58e. As a result, the other end of each fourth reflector electrode finger 58d is indirectly connected to the fourth reflector busbar 8b via the end connection electrode 58e.

[0249] In the second reflector 58, in the region on the side of the third reflector bus bar 8a from the boundary line, the shape of the end connection electrode 58e in a plan view is the same as the shape of the plurality of third reflector electrode fingers 58c and the plurality of fourth reflector electrode fingers 58d in a plan view. Therefore, in this region, the end connection electrode 58e functions to reflect elastic waves, similarly to the plurality of reflector electrode fingers.

[0250] In the present embodiment, when viewed from the direction facing the second reflector bus bar, all the fourth reflector electrode fingers 58d overlap at least the fourth reflector bus bar 8b. In the region of the second reflector 58 on the side of the fourth reflector bus bar 8b from the boundary line, the propagation direction of the elastic wave is a direction toward the third reflector bus bar 8a, and in this region, the number of the plurality of reflector electrode fingers arranged increases as it goes toward the third reflector bus bar 8a. Thereby, without increasing the size of the second reflector 58, the elastic wave can be suitably confined to the IDT electrode 59 side, and the Q value of the elastic wave device 50 can be increased.

[0251] Since the first reflector 57 and the second reflector 58 have the above-described configuration, the region on the piezoelectric substrate 2 can be used more efficiently.

[0252] In the region of the second reflector 58 on the side of the third reflector bus bar 8a from the boundary line, the propagation direction of the elastic wave is a direction toward the third reflector bus bar 8a, and the number of the plurality of reflector electrode fingers arranged is constant. However, as described above, due to the configuration in the region of the second reflector 58 on the side of the fourth reflector bus bar 8b from the boundary line, the effect of suppressing the increase in the size of the second reflector 58 and suitably confining the elastic wave to the IDT electrode 59 can be obtained.

[0253] In the plurality of electrode fingers in the IDT electrode 59 and the plurality of reflector electrode fingers in the first reflector 57 and the second reflector 58, portions that can be approximated by an arc are connected to each other at the inflection points. Note that, for example, at the inflection points, portions that can be approximated by an elliptical arc may be connected to each other. Alternatively, at the inflection points, curves having a parabolic shape that cannot be approximated by an arc or an elliptical arc may be connected to each other. At the inflection points, curves having an arc shape may be connected to each other, or curves having an elliptical arc shape may be connected to each other.

[0254] In the crossover region A, the shape of each electrode finger in a plan view may have a plurality of inflection points. For example, the crossover region may include three or more curved regions. Similarly, in the first reflector 57 and the second reflector 58, the shape of each reflector electrode finger in a plan view may have a plurality of inflection points. For example, each of the first reflector 57 and the second reflector 58 may include three or more regions.

[0255] Incidentally, the stacked structure of the piezoelectric substrate is not limited to the configuration shown in FIG. 2. The sixth embodiment shows an example in which the elastic wave device has a piezoelectric substrate different from that of the first embodiment.

[0256] FIG. 24 is a schematic front cross-sectional view of the elastic wave device according to the sixth embodiment.

[0257] This embodiment is different from the first embodiment in the stacked structure of the piezoelectric substrate 62. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device 10 of the first embodiment.

[0258] The piezoelectric substrate 62 comprises a support substrate 4, an intermediate layer 65, and a piezoelectric layer 6. The intermediate layer 65 is provided on the support substrate 4. The piezoelectric layer 6 is provided on the intermediate layer 65. In this embodiment, the intermediate layer 65 has a frame-like shape, that is, the intermediate layer 65 has through holes. The support substrate 4 blocks one of the through holes in the intermediate layer 65. The piezoelectric layer 6 blocks the other of the through holes in the intermediate layer 65. As a result, a hollow portion 62c is formed in the piezoelectric substrate 62. A part of the piezoelectric layer 6 and a part of the support substrate 4 face each other with the hollow portion 62c in between.

[0259] In this embodiment, the dominant mode can be reflected back to the piezoelectric layer 6. Therefore, the energy of the elastic wave can be effectively confined to the piezoelectric layer 6. In addition, similar to the first embodiment, the region on the piezoelectric substrate 62 can be used efficiently.

[0260] In the following, we show a first and second modification of the sixth embodiment, in which only the laminated structure of the piezoelectric substrate differs from that of the sixth embodiment. In the first and second modifications, as in the sixth embodiment, the region on the piezoelectric substrate can be used efficiently, and the energy of the elastic waves can be effectively confined to the piezoelectric layer.

[0261] In the first modified example shown in Figure 25, the piezoelectric substrate 62A comprises a support substrate 4, an acoustic reflective film 67, an intermediate layer 65A, and a piezoelectric layer 6. The acoustic reflective film 67 is provided on the support substrate 4. The intermediate layer 65A is provided on the acoustic reflective film 67. The piezoelectric layer 6 is provided on the intermediate layer 65A. The intermediate layer 65A is a low-sound velocity film.

[0262] The acoustic reflective film 67 is a laminate of multiple acoustic impedance layers. Specifically, the acoustic reflective film 67 has multiple low acoustic impedance layers and multiple high acoustic impedance layers. The high acoustic impedance layers are layers with relatively high acoustic impedance. More specifically, the multiple high acoustic impedance layers of the acoustic reflective film 67 are high acoustic impedance layer 67a, high acoustic impedance layer 67c, and high acoustic impedance layer 67e. On the other hand, the low acoustic impedance layers are layers with relatively low acoustic impedance. More specifically, the multiple low acoustic impedance layers of the acoustic reflective film 67 are low acoustic impedance layer 67b and low acoustic impedance layer 67d. The low acoustic impedance layers and high acoustic impedance layers are laminated alternately. The high acoustic impedance layer 67a is the layer located closest to the piezoelectric layer 6 in the acoustic reflective film 67.

[0263] The acoustic reflective film 67 has two low acoustic impedance layers and three high acoustic impedance layers. However, the acoustic reflective film 67 only needs to have at least one low acoustic impedance layer and at least one high acoustic impedance layer.

[0264] For the low acoustic impedance layer, materials such as silicon oxide or aluminum can be used. For the high acoustic impedance layer, materials such as metals like platinum or tungsten, or dielectrics like aluminum nitride or silicon nitride can be used. The material of the intermediate layer 65A may be the same as the material of the low acoustic impedance layer.

[0265] In the second modified example shown in Figure 26, the piezoelectric substrate 62B has a support substrate 64 and a piezoelectric layer 6. The piezoelectric layer 6 is provided directly on the support substrate 64. More specifically, the support substrate 64 has a recess. The piezoelectric layer 6 is provided on the support substrate 64 so as to fill the recess. As a result, a hollow portion is provided in the piezoelectric substrate 62B. In a plan view, the hollow portion overlaps with at least a part of the IDT electrode 9.

[0266] Figure 27 is a schematic front cross-sectional view of an elastic wave apparatus according to the seventh embodiment.

[0267] This embodiment differs from the first embodiment in that the IDT electrode 9 has a protective film 79 instead of the dielectric film 18 shown in Figure 2. The IDT electrode 9 is embedded in the protective film 79. Apart from the above, the elastic wave apparatus of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment.

[0268] Specifically, a protective film 79 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 9. The thickness of the protective film 79 is greater than the thickness of the IDT electrode 9. The IDT electrode 9 is embedded in the protective film 79. This makes the IDT electrode 9 less susceptible to damage.

[0269] The protective film 79 has a first protective layer 79a and a second protective layer 79b. The IDT electrode 9 is embedded in the first protective layer 79a. The second protective layer 79b is provided on top of the first protective layer 79a. As a result, the protective film 79 can provide multiple effects. Specifically, in this embodiment, silicon oxide is used as the material for the first protective layer 79a. This makes it possible to reduce the absolute value of the frequency temperature coefficient (TCF) in the elastic wave apparatus. Thus, the temperature characteristics of the elastic wave apparatus can be improved. Silicon nitride is used for the second protective layer 79b. This makes it possible to improve the moisture resistance of the elastic wave apparatus.

[0270] In addition, in this embodiment as well, the IDT electrode 9, the first reflector 7, and the second reflector 8 are configured in the same manner as in the first embodiment. This allows for efficient use of the region on the piezoelectric substrate 2.

[0271] The materials of the first protective layer 79a and the second protective layer 79b are not limited to those described above. The protective film 79 may be a single layer or a laminate of three or more layers.

[0272] Figure 28 is a schematic front cross-sectional view of an elastic wave apparatus according to the eighth embodiment.

[0273] This embodiment is different from the first embodiment in that the IDT electrodes 9 are provided on both the first main surface 6a and the second main surface 6b of the piezoelectric layer 6. The IDT electrode 9 provided on the second main surface 6b is embedded in the second layer 5b of the intermediate layer 5. Except for the above points, the surface acoustic wave device 80 of this embodiment has the same configuration as the surface acoustic wave device 10 of the first embodiment.

[0274] The IDT electrode 9 provided on the first main surface 6a of the piezoelectric layer 6 and the IDT electrode 9 provided on the second main surface 6b face each other with the piezoelectric layer 6 interposed therebetween. Similarly, the first reflector 7 provided on the first main surface 6a of the piezoelectric layer 6 and the first reflector 7 provided on the second main surface 6b face each other with the piezoelectric layer 6 interposed therebetween. The second reflector 8 provided on the first main surface 6a of the piezoelectric layer 6 and the second reflector 8 provided on the second main surface 6b face each other with the piezoelectric layer 6 interposed therebetween.

[0275] In the surface acoustic wave device 80, on the first main surface 6a, the IDT electrode 9, the first reflector 7, and the second reflector 8 are configured inthe same manner as in the first embodiment. The same applies to the second main surface 6b. As a result, in the piezoelectric substrate 2, the regions on the first main surface 6a and the second main surface 6b of the piezoelectric layer 6 can be efficiently used.

[0276] Note that, for example, the design parameters of the IDT electrodes 9 provided on the first main surface 6a and the second main surface 6b of the piezoelectric layer 6 may be different from each other. The same applies to the first reflectors 7 and the second reflectors 8 provided on the first main surface 6a and the second main surface 6b.

[0277] Hereinafter, the first to third modified examples of the eighth embodiment are shown, in which at least one of the configuration of the electrode provided on the second main surface of the piezoelectric layer and the stacked structure of the piezoelectric substrate is different from that of the eighth embodiment. In the first to third modified examples, unnecessary waves outside the band can be suppressed in the same manner as in the eighth embodiment.

[0278] In the first modified example shown in Figure 29, the piezoelectric substrate 62 is configured in the same way as in the sixth embodiment. Specifically, the piezoelectric substrate 62 has a support substrate 4, an intermediate layer 65, and a piezoelectric layer 6. The IDT electrode 9 provided on the second main surface 6b of the piezoelectric layer 6 is located within the hollow portion 62c. In this modified example, a dielectric film 18 is provided on the second main surface 6b of the piezoelectric layer 6 so as to cover the IDT electrode 9. The material of the dielectric film 18 may be the same as the material of the intermediate layer 65, or it may be a different material from the material of the intermediate layer 65. However, the dielectric film 18 is not necessarily required.

[0279] In the second modified example shown in Figure 30, a plate-shaped electrode 88 is provided on the second main surface 6b of the piezoelectric layer 6. The IDT electrode 9 and the electrode 88 face each other with the piezoelectric layer 6 in between. The electrode 88 is embedded in the second layer 5b.

[0280] In the third modified example shown in Figure 31, the piezoelectric substrate 62 is configured in the same way as in the first modified example, and an electrode 88 similar to that in the second modified example is provided on the second main surface 6b of the piezoelectric layer 6. The electrode 88 is located within the hollow portion 62c. A dielectric film 18 is provided on the second main surface 6b so as to cover the electrode 88. However, the dielectric film 18 is not necessarily required.

[0281] The sixth to eighth embodiments and their respective modifications show examples where the IDT electrode 9, the first reflector 7, and the second reflector 8 have the same configuration as in the first embodiment. The piezoelectric substrates in the sixth to eighth embodiments and their respective modifications can also be used when the configurations of the IDT electrode and each reflector are different from those of the first embodiment. Alternatively, in the present invention, the piezoelectric substrate may consist only of a piezoelectric layer.

[0282] The following describes an example of a procedure for reading the shape of the electrode fingers of the IDT electrode and the reflector electrode fingers of the first and second reflectors.

[0283] First, an image including the electrode finger or reflector electrode finger is acquired using a microscope or similar device. For example, a scanning electron microscope (SEM), optical microscope, or laser scanning microscope may be used.

[0284] Next, the image is processed to allow identification of the electrode finger's end by adjusting the contrast and other parameters. Then, the electrode finger's end is detected, and its coordinate values ​​are extracted. Finally, the extracted contour of the electrode finger's end is approximated by a polynomial curve within an appropriate region size.

[0285] Next, the centroid is determined from the curves at both ends of the electrode finger. Here, the centroid is considered to be a linear centroid. Specifically, the centroid is the line connecting the midpoints of lines that connect any two adjacent points on the curves at both ends.

[0286] Next, the normal direction at each coordinate point is calculated from the curve equation. Then, the electrode finger width, electrode finger pitch, and duty cycle are calculated based on the above normal direction. Here, the electrode finger width is defined as the dimension along the above normal direction of the electrode finger. The electrode finger pitch is defined as the distance between the centers of adjacent electrode fingers in the above normal direction. The duty cycle is defined as the electrode finger width divided by the electrode finger pitch.

[0287] Curvature represents the degree to which a curve or surface is bent. It can also be expressed as curvature by calculating the radius of a locally approximated circular arc at any point on the curve, and then taking the reciprocal of that radius. That is, if the calculated radius is r, the curvature is 1 / r. [Explanation of symbols]

[0288] 2… Piezoelectric substrate 3…Support member 4…Support substrate 5…Middle class 5a, 5b... 1st and 2nd layers 6…Piezoelectric layer 6a, 6b…First and second principal surfaces 7…First reflector 7a, 7b…First and second reflector busbars 7c, 7d...1st and 2nd reflector electrode fingers 8…Second reflector 8a, 8b…Third and fourth reflector busbars 8c, 8d... Third and fourth reflector electrode fingers 9,9A…IDT electrode 10... Elastic wave device 11, 12… First and second offset electrodes 13, 13A... First bus bar 13a...First inner busbar section 13b...First outer busbar section 13c...First connection point 13d…Opening 14, 14A… Second bus bar 14a...Second inner busbar section 14b...Second outer busbar section 14c...Second connection point 14d...Opening 15, 16… First and second electrode fingers 18…Dielectric film 21…Mass addition membrane 25A, 25C... First electrode finger 25a, 25b... Wider section 26A, 26C... Second electrode finger 26a, 26b... Wider section 27,27D…First reflector 27e...End connection electrode 28, 28D, 28E… Second reflector 28e...End connection electrode 29A,29C…IDT electrode 37…First reflector 37e...End connection electrode 38...Second reflector 38e...End connection electrode 40... Elastic wave device 45, 46... First and second electrode fingers 47…First reflector 47c, 47d... First and second reflector electrode fingers 48...Second reflector 48c, 48d... Third and fourth reflector electrode fingers 49…IDT electrode 50... Elastic wave device 55, 56… First and second electrode fingers 57…First reflector 57c, 57d... First and second reflector electrode fingers 57e...End connection electrode 58...Second reflector 58c, 58d... Third and fourth reflector electrode fingers 58e...End connection electrode 59…IDT electrode 62, 62A, 62B… Piezoelectric substrates 62c...Hollow part 64…Support board 65,65A…middle layer 67…Acoustic reflective film 67a... High acoustic impedance layer 67b... Low acoustic impedance layer 67c... High acoustic impedance layer 67d... Low acoustic impedance layer 67e... High acoustic impedance layer 79...Protective film 79a, 79b... First and second protective layers 80... Elastic wave device 88...Electrode 107, 108… First and second reflectors A...Cross area B…Blank area F…Central area H1, H2… First and second edge regions W1, W2… First and second curve regions

Claims

1. A piezoelectric substrate including a piezoelectric layer, An IDT electrode is provided on the piezoelectric layer and has a pair of busbars and a plurality of electrode fingers, On the piezoelectric layer, a first reflector and a second reflector are provided so as to face each other with the IDT electrode in between, and each reflector has a pair of reflector busbars and a plurality of reflector electrode fingers, Equipped with, The shape of the plurality of electrode fingers of the IDT electrode in a plan view is curved, The excitation direction of the elastic wave in any part of any electrode finger among the plurality of electrode fingers is one of the first to third directions. The first direction is perpendicular to the direction in which the electrode finger extends. The second direction is the direction connecting the electrode finger and the shortest distance between the electrode finger and the adjacent electrode finger. The third direction is the direction of the electric field vector generated between the electrode finger and the electrode finger adjacent to it. In the first reflector, the pair of reflector busbars are a first reflector busbar and a second reflector busbar facing each other, and in each of the first reflector and the second reflector, the shape of the plurality of reflector electrode fingers in plan view is curved. The plurality of reflector electrode fingers in the first reflector include a first reflector electrode finger whose both ends are directly connected to the first reflector busbar and the second reflector busbar, and a second reflector electrode finger whose one end is not directly connected to the first reflector busbar, wherein the first reflector electrode finger is located closer to the IDT electrode than the second reflector electrode finger. When viewed from a direction in which the first reflector busbar and the second reflector busbar are facing each other, all of the second reflector electrode fingers overlap with at least one of the first reflector busbar and the second reflector busbar. An elastic wave apparatus in which, in at least a portion of the region of the first reflector, the direction of propagation of elastic waves is toward the second reflector busbar, and in that region, the number of the plurality of reflector electrode fingers increases toward the second reflector busbar.

2. The elastic wave apparatus according to claim 1, wherein one end of the second reflector electrode finger is not connected to an electrode, and the other end is directly connected to the second reflector busbar.

3. The first reflector further has end connecting electrodes connected to the first reflector busbar and the second reflector busbar, The elastic wave apparatus according to claim 1, wherein one end of at least one second reflector electrode finger is indirectly connected to the first reflector busbar via the end connecting electrode, and the other end is directly connected to the second reflector busbar.

4. The first reflector further has end connecting electrodes connected to the first reflector busbar and the second reflector busbar, At least one end of the second reflector electrode finger is indirectly connected to the first reflector busbar via the end-connecting electrode, and the other end is indirectly connected to the second reflector busbar via the end-connecting electrode, The elastic wave apparatus according to claim 1, wherein in a portion of the region of the first reflector, the direction of propagation of elastic waves is toward the second reflector busbar, and in that region, the number of the plurality of reflector electrode fingers increases toward the second reflector busbar, and in another portion of the region, the direction of propagation of elastic waves is toward the first reflector busbar, and in that region, the number of the plurality of reflector electrode fingers increases toward the first reflector busbar.

5. The elastic wave apparatus according to any one of claims 1 to 4, wherein, when viewed from a direction in which the first reflector busbar and the second reflector busbar are facing each other, at least a portion of all of the second reflector electrode fingers overlaps with both the first reflector busbar and the second reflector busbar.

6. In the second reflector, the pair of reflector busbars are a third reflector busbar and a fourth reflector busbar facing each other. The plurality of reflector electrode fingers in the second reflector include a third reflector electrode finger whose both ends are directly connected to the third reflector busbar and the fourth reflector busbar, and a fourth reflector electrode finger whose one end is not directly connected to the fourth reflector busbar, wherein the third reflector electrode finger is located closer to the IDT electrode than the fourth reflector electrode finger. When viewed from a direction in which the third reflector busbar and the fourth reflector busbar are facing each other, all of the fourth reflector electrode fingers overlap with at least one of the third reflector busbar and the fourth reflector busbar. The elastic wave apparatus according to any one of claims 1 to 5, wherein in at least a portion of the region of the second reflector, the direction of propagation of the elastic wave is toward the third reflector busbar, and in that region, the number of the plurality of reflector electrode fingers increases toward the third reflector busbar.

7. The elastic wave apparatus according to claim 6, wherein, when viewed from a direction in which the third reflector busbar and the fourth reflector busbar are facing each other, all of the fourth reflector electrode fingers overlap with both the third reflector busbar and the fourth reflector busbar.

8. The elastic wave apparatus according to any one of claims 1 to 7, wherein the number of multiple reflector electrode fingers in the first reflector and the number of multiple reflector electrode fingers in the second reflector are different from each other.

9. The elastic wave apparatus according to any one of claims 1 to 8, wherein at least one of the electrode finger pitch and duty cycle is constant in the portion of the IDT electrode where the excitation direction is the same.

10. The plurality of electrode fingers in the IDT electrode include a plurality of first electrode fingers and a plurality of second electrode fingers that are interlocked with each other. The imaginary line formed by connecting the tips of the multiple second electrode fingers is called the first envelope, and the imaginary line formed by connecting the tips of the multiple first electrode fingers is called the second envelope. The region between the first envelope and the second envelope in the IDT electrode is called the intersection region. The elastic wave apparatus according to any one of claims 1 to 9, wherein the resonant frequency or anti-resonant frequency of the main mode substantially coincides in the crossover region.

11. In the IDT electrode, the pair of busbars are a first busbar and a second busbar facing each other, the plurality of electrode fingers are a plurality of first electrode fingers and a plurality of second electrode fingers, one end of each of the plurality of first electrode fingers is connected to the first busbar, one end of each of the plurality of second electrode fingers is connected to the second busbar, and the plurality of first electrode fingers and the plurality of second electrode fingers are interlocked with each other. The IDT electrode further comprises a plurality of offset electrodes, each having one end connected to at least the first busbar of the pair of busbars. The elastic wave apparatus according to any one of claims 1 to 10, wherein the other end of each of the plurality of offset electrodes, one end of which is connected to the first busbar, faces the plurality of second electrode fingers across a gap.

12. In the IDT electrode, the pair of busbars are a first busbar and a second busbar facing each other. Of the pair of busbars, at least the first busbar has an inner busbar portion and an outer busbar portion that face each other, and a plurality of connecting portions that connect the inner busbar portion and the outer busbar portion. In the first busbar, of the inner busbar portion and the outer busbar portion, the inner busbar portion is located on the side of the second busbar. The elastic wave apparatus according to any one of claims 1 to 10, wherein the first busbar is provided with a plurality of openings surrounded by the inner busbar portion, the outer busbar portion, and the plurality of connecting portions.

13. The plurality of electrode fingers in the IDT electrode are a plurality of first electrode fingers and a plurality of second electrode fingers that are interlocked with each other. The imaginary line formed by connecting the tips of the multiple second electrode fingers is called the first envelope, and the imaginary line formed by connecting the tips of the multiple first electrode fingers is called the second envelope. The region between the first envelope and the second envelope in the IDT electrode is called the intersection region. The intersection region comprises a first edge region including the first envelope, a second edge region including the second envelope, and a central region sandwiched between the first and second edge regions. The elastic wave apparatus according to any one of claims 1 to 12, wherein in at least one of the first edge region and the second edge region, at least one of the electrode fingers has a wide portion that is wider than the width in the central region.

14. The plurality of electrode fingers in the IDT electrode are a plurality of first electrode fingers and a plurality of second electrode fingers that are interlocked with each other. The imaginary line formed by connecting the tips of the multiple second electrode fingers is called the first envelope, and the imaginary line formed by connecting the tips of the multiple first electrode fingers is called the second envelope. The region between the first envelope and the second envelope in the IDT electrode is called the intersection region. The intersection region comprises a first edge region including the first envelope, a second edge region including the second envelope, and a central region sandwiched between the first and second edge regions. The acoustic wave apparatus according to any one of claims 1 to 13, further comprising a mass-adding film provided in at least one of the first edge region and the second edge region such that, when viewed from above, it overlaps with at least one of the plurality of first electrode fingers and the plurality of second electrode fingers.

15. The plurality of electrode fingers in the IDT electrode are a plurality of first electrode fingers and a plurality of second electrode fingers that are interlocked with each other. The imaginary line formed by connecting the tips of the multiple second electrode fingers is called the first envelope, and the imaginary line formed by connecting the tips of the multiple first electrode fingers is called the second envelope. The region between the first envelope and the second envelope in the IDT electrode is called the intersection region. The intersection region comprises a first edge region including the first envelope, a second edge region including the second envelope, and a central region sandwiched between the first and second edge regions. The elastic wave apparatus according to any one of claims 1 to 14, wherein in at least one of the first edge region and the second edge region, at least one of the electrode fingers is thicker than the thickness in the central region.

16. The piezoelectric substrate has a support substrate, The elastic wave apparatus according to any one of claims 1 to 15, wherein the piezoelectric layer is provided on the support substrate.

17. The elastic wave apparatus according to claim 16, wherein the piezoelectric substrate has an intermediate layer provided between the support substrate and the piezoelectric layer.

18. The elastic wave apparatus according to claim 16 or 17, wherein a hollow portion is formed in the piezoelectric substrate, and a part of the support substrate and a part of the piezoelectric layer face each other with the hollow portion in between.

19. The elastic wave apparatus according to any one of claims 1 to 15, wherein the piezoelectric substrate consists only of the piezoelectric layer.

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