Elastic wave apparatus and filter apparatus

Abstract

The present invention provides an elastic wave device that suppresses transverse modes and reduces energy leakage of elastic waves. [Solution] The elastic wave apparatus comprises a piezoelectric substrate including a piezoelectric layer and an IDT electrode 9 having a plurality of first floating electrodes 11. The intersection region A has a central region F located on the central side in the propagation orthogonal direction perpendicular to the elastic wave propagation direction, and a first edge region H1 and a second edge region H2 facing each other with the central region F in between. The plurality of first floating electrodes 11 are located between the first edge region H1 and the first bus bar 13. The region located between the first edge region H1 and the first bus bar 13, where the plurality of first floating electrodes 11 are provided, is the first floating electrode formation region U1. The elastic wave apparatus further comprises a first mass addition film 8A provided in the first edge region H1 and a second mass addition film 8B provided in the first floating electrode formation region U1.

Description

Technical Field

[0001] The present invention relates to an elastic wave device and a filter device.

[0002] Conventionally, elastic wave devices have been widely used in filters of mobile phones and the like. In an elastic wave device, various unwanted waves occur in addition to the main mode used for forming the filter band. For example, a transverse mode occurs at a frequency between the resonance frequency and the anti-resonance frequency of the main mode. In order to obtain a good response of the main mode, it is important to suppress the response of unwanted waves such as the transverse mode.

[0003] Patent Document 1 below discloses an example of an elastic wave device. In this elastic wave device, a high sound velocity member, a low sound velocity film, and a piezoelectric film are laminated in this order. An IDT electrode is provided on the piezoelectric film.

[0004] The IDT electrode has a pair of bus bars and a plurality of electrode fingers. A plurality of openings are provided in each bus bar. One end portion of each of the plurality of electrode fingers is connected to one of the pair of bus bars. The portions and tip portions of the plurality of electrode fingers that are connected to the bus bars are made into thick portions that are wider than the widths of the other portions. With such a configuration, the transverse mode can be suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the elastic wave device described in Patent Document 1, there are cases where the leakage of the energy of the elastic wave from the region where the plurality of electrode fingers are provided to the bus bar side cannot be sufficiently suppressed.

[0007] An object of the present invention is to provide an elastic wave device that can suppress a transverse mode and suppress leakage of elastic wave energy.

Means for Solving the Problems

[0008] In a broad aspect of the elastic wave device according to the present invention, a piezoelectric substrate including a piezoelectric layer, an IDT electrode provided on the piezoelectric layer and having a pair of bus bars, a plurality of electrode fingers, and a plurality of first floating electrodes not connected to the pair of bus bars and the plurality of electrode fingers are provided. The pair of bus bars are a first bus bar and a second bus bar facing each other. The plurality of electrode fingers are a plurality of first electrode fingers and a plurality of second electrode fingers. One end portion of each of the plurality of first electrode fingers is connected to the first bus bar, and one end portion of each of the plurality of second electrode fingers is connected to the second bus bar. The plurality of first electrode fingers and the plurality of second electrode fingers are interposed with each other. In the elastic wave propagation direction, a region where adjacent first electrode fingers and second electrode fingers overlap is a crossing region. When a direction orthogonal to the elastic wave propagation direction is defined as a propagation orthogonal direction, the crossing region has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region that sandwich the central region and face each other. The first edge region is located on the first bus bar side, and the second edge region is located on the second bus bar side. The plurality of first floating electrodes are located between the first edge region and the first bus bar. A region where the plurality of first floating electrodes are provided is a first floating electrode formation region. The elastic wave device further includes a first mass addition film provided in the first edge region and a second mass addition film provided in the first floating electrode formation region.

[0009] In another broad aspect of the elastic wave apparatus according to the present invention, a piezoelectric substrate including a piezoelectric layer and an IDT electrode provided on the piezoelectric layer having a pair of busbars, a plurality of electrode fingers, and a plurality of first floating electrodes not connected to the pair of busbars and the plurality of electrode fingers, wherein 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, the plurality of first electrode fingers and the plurality of second electrode fingers are interlocked with each other, the region where adjacent first electrode fingers and second electrode fingers overlap in the elastic wave propagation direction is the crossing region, and when the direction perpendicular to the elastic wave propagation direction is defined as the propagation orthogonal direction, the crossing region is The device has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region facing each other with the central region in between, wherein the first edge region is located on the first busbar side, and the second edge region is located on the second busbar side, and the plurality of first floating electrodes are located between the first edge region and the first busbar, and the region where the plurality of first floating electrodes are provided is the first floating electrode forming region, wherein in the first edge region, at least one of the plurality of first electrode fingers and the plurality of second electrode fingers has a first wide portion that is wider than the width in the central region, and in the first floating electrode forming region, the plurality of first electrode fingers have a second wide portion that is wider than the width in the central region, and at least one of the configurations in which the plurality of first floating electrodes have a second wide portion that is wider than the other portions.

[0010] In yet another broad aspect of the elastic wave apparatus according to the present invention, the apparatus comprises a piezoelectric substrate including a piezoelectric layer, and an IDT electrode provided on the piezoelectric layer, having a pair of busbars, a plurality of electrode fingers, and a plurality of first floating electrodes not connected to the pair of busbars and the plurality of electrode fingers, wherein 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, the plurality of first electrode fingers and the plurality of second electrode fingers are interlocked with each other, and in the direction of elastic wave propagation, the region where adjacent first electrode fingers and second electrode fingers overlap is the cross region, and the direction perpendicular to the direction of elastic wave propagation When the direction is perpendicular to the propagation direction, the intersection region has a central region located on the central side in the perpendicular to the propagation direction, and a first edge region and a second edge region facing each other with the central region in between, the first edge region located on the first busbar side, and the second edge region located on the second busbar side, the plurality of first floating electrodes are located between the first edge region and the first busbar, the region where the plurality of first floating electrodes are provided is the first floating electrode forming region, and a first mass-adding film is further provided on the first edge region, and in the first floating electrode forming region, at least one of the following configurations is provided: the plurality of first electrode fingers have a second wide portion that is wider than the width in the central region, and the plurality of first floating electrodes have a second wide portion that is wider than the other portions.

[0011] In yet another broad aspect of the elastic wave apparatus according to the present invention, the apparatus comprises a piezoelectric substrate including a piezoelectric layer, and an IDT electrode provided on the piezoelectric layer, having a pair of busbars, a plurality of electrode fingers, and a plurality of first floating electrodes not connected to the pair of busbars and the plurality of electrode fingers, wherein 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, the plurality of first electrode fingers and the plurality of second electrode fingers are interlocked with each other, and in the direction of elastic wave propagation, the region where adjacent first electrode fingers and second electrode fingers overlap is an intersection region. Yes, when the direction perpendicular to the elastic wave propagation direction is defined as the propagation orthogonal direction, the intersection region has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region facing each other with the central region in between, the first edge region located on the first busbar side, and the second edge region located on the second busbar side, the plurality of first floating electrodes are located between the first edge region and the first busbar, the region in which the plurality of first floating electrodes are provided is the first floating electrode forming region, in the first edge region, at least one of the plurality of first electrode fingers and the plurality of second electrode fingers has a first wide portion that is wider than the width in the central region, and a second mass-adding film is provided in the first floating electrode forming region. [Effects of the Invention]

[0012] According to the elastic wave apparatus of the present invention, transverse modes can be suppressed, and leakage of elastic wave energy can be suppressed. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic plan view of an elastic wave apparatus according to the first embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view along line II in Figure 1. [Figure 3] This is a schematic plan view showing an enlarged view of the area enclosed by the dashed line C in Figure 1. [Figure 4] This 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 comparative example. [Figure 5] This figure shows the impedance frequency characteristics in the first embodiment of the present invention and the first comparative example. [Figure 6] This figure shows the return loss in the first embodiment of the present invention and the first comparative example. [Figure 7] This is a schematic plan view showing a magnified view of the area around the first busbar of the IDT electrode in the second comparative example. [Figure 8] This figure shows the impedance frequency characteristics in the first embodiment and the second comparative example of the present invention. [Figure 9] This figure shows the return loss in the first embodiment and the second comparative example of the present invention. [Figure 10] This is a schematic plan view showing a magnified view of the area around the first busbar of the IDT electrode in the third comparative example. [Figure 11] This is a schematic plan view showing a magnified view of the area around the first busbar of the IDT electrode in the fourth comparative example. [Figure 12] This figure shows the impedance frequency characteristics in the first embodiment, the third comparative example, and the fourth comparative example of the present invention. [Figure 13] This figure shows the return loss in the first embodiment, the third comparative example, and the fourth comparative example of the present invention. [Figure 14] This is a schematic plan view showing a circle containing an arc, when the shape of the electrode finger in a plan view of the IDT electrode in the first embodiment of the present invention is approximated as a circular arc. [Figure 15] This is a schematic plan view showing an enlarged view of the area around the first busbar of the IDT electrode in a first modified example of the first embodiment of the present invention. [Figure 16]This is a schematic plan view showing an enlarged view of the area around the first busbar of the IDT electrode in a second modified example of the first embodiment of the present invention. [Figure 17] 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 third modified example of the first embodiment of the present invention. [Figure 18] 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 second embodiment of the present invention. [Figure 19] 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 modification of a second embodiment of the present invention. [Figure 20] 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 second modified example of the second embodiment of the present invention. [Figure 21] 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 third modified example of the second embodiment of the present invention. [Figure 22] This is a schematic front cross-sectional view showing a portion of the elastic wave apparatus according to a third embodiment of the present invention, passing through a first edge region. [Figure 23] This is a schematic front cross-sectional view showing a portion of an elastic wave apparatus according to a modified third embodiment of the present invention, passing through a first edge region. [Figure 24] This is a schematic front cross-sectional view showing a portion of the elastic wave apparatus according to a fourth embodiment of the present invention, passing through a first edge region. [Figure 25] 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 fifth embodiment of the present invention. [Figure 26] 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 the fifth embodiment of the present invention. [Figure 27] 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 second modified example of the fifth embodiment of the present invention. [Figure 28] This is a schematic plan view of an elastic wave apparatus according to a sixth embodiment of the present invention. [Figure 29] This is a schematic plan view showing a magnified view of multiple electrode fingers of an IDT electrode in a modified example of the sixth embodiment of the present invention. [Figure 30] 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 seventh embodiment of the present invention. [Figure 31] This is a schematic plan view of an elastic wave apparatus according to the eighth embodiment of the present invention. [Figure 32] This is a schematic plan view showing the parallel and non-parallel regions in the eighth embodiment of the present invention. [Figure 33] This is a schematic front cross-sectional view of an elastic wave apparatus according to the ninth embodiment of the present invention. [Figure 34] This is a schematic front cross-sectional view of an elastic wave apparatus according to a first modification of the ninth embodiment of the present invention. [Figure 35] This is a schematic front cross-sectional view of an elastic wave apparatus according to a second modified example of the ninth embodiment of the present invention. [Figure 36] This is a schematic front cross-sectional view of an elastic wave apparatus according to the tenth embodiment of the present invention. [Figure 37] This is a schematic front cross-sectional view of an elastic wave apparatus according to a first modification of the tenth embodiment of the present invention. [Figure 38] This is a schematic front cross-sectional view of an elastic wave apparatus according to a second modified example of the tenth embodiment of the present invention. [Figure 39] This is a schematic front cross-sectional view of an elastic wave apparatus according to a third modified example of the tenth embodiment of the present invention. [Figure 40] This is a circuit diagram of a filter device according to the 11th embodiment of the present invention. [Modes for carrying out the invention]

[0014] The present invention will be clarified below by describing specific embodiments of the present invention with reference to the drawings.

[0015] It should be noted that the embodiments described herein are illustrative, and that partial substitution or combination of configurations is possible between different embodiments.

[0016] 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. In Figure 1, the IDT electrodes and each reflector, which will be described later, are shown by schematic diagrams with two diagonal lines added to the contour figures. Note that the dielectric film, which will be described later, is omitted in Figure 1.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] A dielectric film 19 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 9. Specifically, the dielectric film 19 is provided on the first main surface 6a of the piezoelectric layer 6. Since the IDT electrode 9 is protected by the dielectric film 19, the IDT electrode 9 is less likely to be damaged. In this embodiment, silicon oxide is used as the material for the dielectric film 19. However, the material for the dielectric film 19 is not limited to the above. Note that the dielectric film 19 is not necessarily required.

[0021] Figure 3 is a schematic plan view showing an enlarged view of the area enclosed by the dashed line C in Figure 1. Note that the dielectric film 19 is omitted in Figure 3.

[0022] 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.

[0023] The second busbar 14 is provided with a plurality of openings 14d. More specifically, the second busbar 14 has an inner busbar portion 14a and an outer busbar portion 14b, and a plurality of connecting portions 14c. The inner busbar portion 14a and the outer busbar portion 14b face each other. Of the inner busbar portion 14a and the outer busbar portion 14b, the inner busbar portion 14a is located on the side of the first busbar 13. The plurality of connecting portions 14c connect the inner busbar portion 14a and the outer busbar portion 14b. Each of the plurality of openings 14d is an opening surrounded by the inner busbar portion 14a, the outer busbar portion 14b, and the plurality of connecting portions 14c.

[0024] The inner busbar portion 14a and the outer busbar portion 14b extend in parallel. Therefore, the distance between the inner busbar portion 14a and the outer busbar portion 14b is constant. That is, when the length of the multiple openings 14d is defined as the dimension of the multiple openings 14d along the direction perpendicular to the direction in which the inner busbar portion 14a extends, the length of the multiple openings 14d is constant. On the other hand, the first busbar 13 does not have any openings.

[0025] 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."

[0026] The shapes of the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 in a plan view include curved shapes. 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.

[0027] In this embodiment, specifically, the plan view shape of the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 is curved. In this invention, the plan view shape of the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 may include both curved and straight portions. Alternatively, the shape may be entirely straight.

[0028] The multiple first electrode fingers 15 and multiple second electrode fingers 16 shown in Figure 3 each include 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 base 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 base end and the tip end.

[0029] 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.

[0030] In this embodiment, the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends are parallel. The directions in which the first envelope E1 and the second envelope E2 extend are parallel to the direction in which the propagation axis extends. The direction in which the first envelope E1 extends and the directions in which the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 extend intersect but are not perpendicular. Similarly, the direction in which the second envelope E2 extends and the directions in which the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 extend intersect but are not perpendicular. Note that the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends may intersect.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In cross 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 1st to 3rd directions: The 1st direction is perpendicular to the direction in which the electrode finger extends. The 2nd direction is the direction connecting the shortest distance between the electrode finger and the adjacent 1st electrode finger 15 or 2nd electrode finger 16. The 3rd direction is the direction of the electric field vector generated between the electrode finger and the adjacent 1st electrode finger 15 or 2nd electrode finger 16.

[0035] Figure 3 shows an example of the elastic wave propagation direction indicated by the double-headed arrow B1. The excitation direction of the elastic wave and the elastic wave propagation direction can, strictly speaking, be different from each other. However, in this invention, treating the excitation direction of the elastic wave and the elastic wave propagation direction as the same does not have a significant effect. Therefore, in this specification, the excitation direction of the elastic wave and the elastic wave propagation direction will be treated as being the same direction.

[0036] 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.

[0037] First, each electrode finger has a curved edge. If a virtual line is drawn parallel to the direction in which the propagation axis extends, connecting both end edges at any point on the electrode finger, the centroid of the portion located on this virtual line is taken as the representative point on the virtual line. Numerous virtual lines can be drawn on an electrode finger, and therefore, there are countless representative points. The direction in which the tangents of the curves connecting these representative points extend is taken as the direction in which the electrode finger extends.

[0038] The excitation angle θ is the angle between the excitation direction of the elastic wave and the direction in which the propagation axis of the piezoelectric layer 6 extends. C_prop In this embodiment, the shape of each electrode finger in plan view within the intersection region A is curved. Therefore, in the intersection region A, the excitation angle θ C_prop The conditions are not uniform. Therefore, in the intersection region A, the excitation direction of the elastic waves is not uniform.

[0039] Returning to Figure 1, in this embodiment, the portion through which the second envelope E2 passes is the excitation angle θ. C_prop This is the region where the angle is 0°. Excitation angle θ C_prop The portions where the angle is 0° are aligned in a straight line. On the other hand, as shown by the curve M, in this embodiment, the excitation angle θ C_prop The excitation angle θ is not 0°, and C_prop When the same region is connected, the resulting line is curved. In other words, the line connecting the regions where the excitation direction of the elastic waves is the same is curve M.

[0040] However, the curve M is for excitation angles θ C_prop other than 0°, and is an example of a portion where the excitation angles θ C_prop are the same. In the crossing region A, there are innumerable curves similar to the curve M. Thus, the shapes of the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 in plan view are such that portions where the excitation angles θ C_prop are other than 0° and the same are arranged in a curved line shape.

[0041] Note that in this specification, the positive direction of the excitation angle θ C_prop is the counterclockwise direction when viewed in plan view. In this embodiment, in any portion of the crossing region A, the excitation angle θ C_prop is 0° or more. However, in the present invention, the crossing region A may include a portion where the excitation angle θ C_prop is less than 0°.

[0042] As shown in FIG. 3, the crossing region A has a central region F and a pair of edge regions. When the direction orthogonal to the elastic wave propagation direction is defined as the propagation orthogonal direction, the central region F is located on the central side in the propagation orthogonal direction in the crossing region A. In this embodiment, the central region F is located on the central side in the direction in which the first bus bar 13 and the second bus bar 14 face each other in the crossing region A. The pair of edge regions are specifically the first edge region H1 and the second edge region H2. The first edge region H1 and the second edge region sandwich the central region F and face each other.

[0043] The first edge region H1 is located on the side of the first bus bar 13. The first edge region H1 includes the first envelope line E1 as an edge portion. The second edge region H2 is located on the side of the second bus bar 14. The second edge region H2 includes the second envelope line E2 as an edge portion.

[0044] The ranges of the first edge region H1 and the second edge region H2 are based on a wavelength λ defined by the electrode finger pitch. The electrode finger pitch is the distance between the centers of adjacent first electrode fingers 15 and second electrode fingers 16. When the electrode finger pitch is p, λ = 2p.

[0045] The first edge region H1 is defined as a region extending approximately 1λ from the first envelope E1 along the normal direction of the first envelope E1. Similarly, the second edge region H2 is defined as a region extending approximately 1λ from the second envelope E2 along the normal direction of the second envelope E2. In addition, the first edge region H1 and the second edge region H2 include the entire thickness of the elastic wave apparatus 10. For example, the intermediate layer 5 shown in Figure 2 also includes the first edge region H1 and the second edge region H2.

[0046] 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 excitation angle θ is 0°. In this embodiment, the excitation angle θ C_prop The portion where the angle is 0° is the portion on the second envelope E2.

[0047] As shown in Figure 3, the IDT electrode 9 further has a plurality of floating electrodes. Specifically, the plurality of floating electrodes in this embodiment are a plurality of first floating electrodes 11. The plurality of first floating electrodes 11 are located between the first edge region H1 and the first bus bar 13. The plurality of first floating electrodes 11 are not connected to the first bus bar 13, the second bus bar 14, the plurality of first electrode fingers 15, and the plurality of second electrode fingers 16. The plurality of first floating electrodes 11 and the plurality of first electrode fingers 15 are arranged alternately. The region located between the first edge region H1 and the first bus bar 13, where the plurality of first floating electrodes 11 are provided, is the first floating electrode forming region U1.

[0048] More specifically, the first floating electrode formation region U1 is a band-shaped region in which multiple first floating electrodes 11 and multiple first electrode fingers 15 are arranged alternately. The first floating electrode formation region U1 includes the entire thickness of the elastic wave apparatus 10. For example, the intermediate layer 5 shown in Figure 2 is also included in the first floating electrode formation region U1.

[0049] As shown in Figure 3, the tips of the multiple second electrode fingers 16 face one end of the multiple first floating electrodes 11, separated by a gap. The region where the gap between the multiple second electrode fingers 16 and the multiple first floating electrodes 11 is located is the first gap region G1. The other ends of the multiple first floating electrodes 11 face the first busbar 13, separated by a gap. The region where the gap between the multiple first floating electrodes 11 and the first busbar 13 is located is the second gap region G2.

[0050] The planar shapes of the multiple first floating electrodes 11 are curved. Specifically, the planar shapes of the multiple first floating electrodes 11 are shapes that can be approximated by circular arcs. Furthermore, when the planar shapes of any one first floating electrode 11 and the second electrode finger 16 facing the first floating electrode 11 are approximated by circular arcs, the circle containing each of these arcs is the same circle.

[0051] The ends of the multiple first floating electrodes 11 on the side of the first busbar 13 are defined as the tips of the multiple first floating electrodes 11. Each of the tips of the multiple first floating electrodes 11 includes its tip. The imaginary line formed by connecting the tips of the multiple first floating electrodes 11 is defined as the third envelope E3. In this case, the region between the third envelope E3 and the first busbar 13 is the second gap region G2.

[0052] The direction in which the third envelope E3 extends intersects with the direction in which the multiple first floating electrodes 11 extend, and are not orthogonal. Similarly, the direction in which the first envelope E1 extends intersects with the direction in which the multiple first floating electrodes 11 extend, and are not orthogonal.

[0053] In this embodiment, when the width of the first gap region G1 is defined as the dimension of the first gap region G1 along the normal direction of the first envelope E1, the width of the first gap region G1 is less than 1λ. In this embodiment, when the width of the second gap region G2 is defined as the dimension of the second gap region G2 along the normal direction of the third envelope E3, the width of the second gap region G2 is less than 1λ. However, the widths of the first gap region G1 and the second gap region G2 are not limited to the above.

[0054] In this embodiment, no floating electrodes are provided on the second busbar 14 side. Therefore, the tips of the multiple first electrode fingers 15 face the second busbar 14 with a gap between them. The region where the gap between the multiple first electrode fingers 15 and the first busbar 13 is located is the gap region G.

[0055] A mass-adding film is provided in each of the first edge region H1, the first floating electrode formation region U1, and the second edge region H2. Specifically, a first mass-adding film 8A is provided in the first edge region H1. A second mass-adding film 8B is provided in the first floating electrode formation region U1. A third mass-adding film 8C is provided in the second edge region H2.

[0056] The first mass-adding film 8A has a strip-like shape. The first mass-adding film 8A is continuously provided over multiple electrode fingers. Similarly, the second mass-adding film 8B and the third mass-adding film 8C also have a strip-like shape. The second mass-adding film 8B is also continuously provided over multiple electrode fingers. Therefore, the first mass-adding film 8A and the second mass-adding film 8B are also provided on the piezoelectric layer 6 in the portions between the electrode fingers. The third mass-adding film 8C is continuously provided over multiple first floating electrodes 11 and multiple first electrode fingers 15. Therefore, the third mass-adding film 8C is also provided on the piezoelectric layer 6 in the portions between the first floating electrodes 11 and the first electrode fingers 15.

[0057] In the following, the width of the first mass-adding film 8A is defined as the dimension of the first mass-adding film 8A along the direction normal to the first envelope E1. The width of the second mass-adding film 8B is defined as the dimension of the second mass-adding film 8B along the direction normal to the third envelope E3. The width of the third mass-adding film 8C is defined as the dimension of the third mass-adding film 8C along the direction normal to the second envelope E2.

[0058] Returning to Figure 1, a pair of reflectors is provided on the piezoelectric layer 6. Specifically, the pair of reflectors are reflector 7A and reflector 7B. Reflectors 7A and 7B face each other, flanking the IDT electrode 9 in the direction in which the multiple electrode fingers of the IDT electrode 9 are aligned.

[0059] Reflector 7A and reflector 7B each have a pair of reflector busbars and a plurality of reflector electrode fingers. In reflector 7A, one end of each of the plurality of reflector electrode fingers is connected to one reflector busbar, and the other end of each of the plurality of reflector electrode fingers is connected to the other reflector busbar. The same applies to reflector 7B.

[0060] The shape of the multiple reflector electrode fingers in reflectors 7A and 7B in a plan view includes a curved shape. Specifically, the multiple reflector electrode fingers in reflectors 7A and 7B have a shape that corresponds to the multiple electrode fingers of the IDT electrode 9. As a result, the elastic waves can be effectively reflected towards the IDT electrode 9 by reflectors 7A and 7B.

[0061] More specifically, in reflectors 7A and 7B, the shape of the multiple reflector electrode fingers is curved so that in the intersection region A, the portions of the elastic waves with the same excitation direction are aligned in the trajectory that is continuous with the trajectory, and the portions of the elastic waves with the same propagation direction are aligned. However, the shape of the multiple reflector electrode fingers of reflectors 7A and 7B is not limited to the above.

[0062] A key feature of this embodiment is that a first mass-adding film 8A is provided in the first edge region H1, and a second mass-adding film 8B is provided in the first floating electrode formation region U1. This suppresses transverse modes and reduces energy leakage of elastic waves. The details of this will be explained below by comparing this embodiment with the first comparative example.

[0063] The first comparative example shown in Figure 4 differs from the first embodiment in that the IDT electrode 209A does not have multiple floating electrodes, and the first busbar 203 has multiple openings 203d. In the first comparative example, the multiple second electrode fingers 16 face the first busbar 203 with a gap between them. A first mass-adding film 8A is provided in the first edge region H1. A third mass-adding film 8C is provided in the second edge region H2.

[0064] An elastic wave apparatus 10 having the configuration of the first embodiment and an elastic wave apparatus of the first comparative example were prepared, and their impedance frequency characteristics and return loss were compared. The design parameters of the elastic wave apparatus 10 having the configuration of the first embodiment are as follows. Here, the length of the floating electrode is defined as the dimension along the direction in which the floating electrode extends. The width of the inner busbar portion of the busbar having multiple openings is defined as the dimension along the direction perpendicular to the direction in which the inner busbar portion extends.

[0065] Support substrate: Material...Si, plane orientation...(111), Euler angle (φ,θ,ψ) ψ...73° Intermediate layer, first layer: Material...SiN, Thickness...0.15λ Second layer of the intermediate layer: Material...SiO2, Thickness...0.15λ Piezoelectric layer: Material... LiTaO3 with rotational Y-cut 55° X-propagation, thickness... 0.2λ IDT electrode: Material...Al, Thickness...0.05λ Dielectric film: Material...SiO2, Thickness...0.02λ Wavelength λ: Excitation angle θ C_prop 2 μm in the region where the angle is 0° Number of electrode fingers in IDT electrodes: 90 pairs Distance between the first and second envelopes: 27.8λ Duty cycle: Excitation angle θ C_prop 0.5 Number of reflector electrode fingers in each reflector: 20 pairs Width of the first mass-addition film: 0.72λ Width of the first gap region: 0.135λ Length of the first floating electrode: 1λ Width of the second mass-addition film: 0.72λ Width of the second gap region: 0.135λ Width of the third mass-addition film: 0.62λ Width of the inner busbar section in the second busbar: 0.2λ Opening length of the opening in the second busbar: 2λ

[0066] Here, we show an example where the widths of the first and second mass-adding films are the same. However, the widths of the first and second mass-adding films may be different.

[0067] Figure 5 shows the impedance frequency characteristics in the first embodiment and the first comparative example. Figure 6 shows the return loss in the first embodiment and the first comparative example.

[0068] As shown in Figure 5, there is no significant difference between the first embodiment and the first comparative example in terms of impedance frequency characteristics. Therefore, the relative bandwidths of the first embodiment and the first comparative example are almost identical. The relative bandwidth is expressed as (|fa-fr| / fr)×100[%], where fr is the resonant frequency and fa is the anti-resonant frequency.

[0069] In addition, the capacitances are almost identical in the first embodiment and the first comparative example. More specifically, capacitance correlates with impedance at frequencies lower than the resonant frequency fr. In the first embodiment and the first comparative example, the impedances at frequencies lower than the resonant frequency fr are almost identical. Therefore, the capacitances are also almost identical in the first embodiment and the first comparative example.

[0070] As shown in Figure 6, transverse modes are suppressed in the first embodiment and the first comparative example. Transverse modes are unwanted waves that occur at frequencies between the resonant frequency fr and the anti-resonant frequency fa. Transverse modes are suppressed for the following reasons.

[0071] In the first embodiment shown in Figure 3, the first mass-adding film 8A is provided in the first edge region H1, so that the speed of sound in the first edge region H1 is lower than the speed of sound in the central region F. As a result, a low-speed region is formed in the first edge region H1. A low-speed region is a region where the speed of sound is lower than the speed of sound in the central region F. In the second edge region H2, a low-speed region is also formed by providing a third mass-adding film 8C. The same applies to the first comparative example.

[0072] In addition, in the first gap region G1 of the first embodiment, only the multiple first electrode fingers 15 are provided among the multiple first electrode fingers 15 and multiple second electrode fingers 16. On the other hand, in the crossing region A, the first electrode fingers 15 and the second electrode fingers 16 are arranged alternately. Therefore, the speed of sound in the first gap region G1 is higher than the speed of sound in the crossing region A. As a result, a high-speed region is formed in the first gap region G1. A high-speed region is a region where the speed of sound is higher than the speed of sound in the central region F. Similarly, a high-speed region is also formed in the gap region G on the second busbar 14 side.

[0073] On the other hand, in the first embodiment, each of the multiple connection portions 14c of the second busbar 14 extends along the extension of the second electrode finger 16. None of the multiple connection portions 14c are located along the extension of the first electrode finger 15. 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 second busbar 14 where the multiple openings 14d 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 second busbar 14 where the multiple openings 14d are formed.

[0074] In the first comparative example shown in Figure 4, high-sonic-velocity regions are formed in the areas where gaps are located between multiple second electrode fingers 16 and the first bus bar 203, and in the areas where gaps are located between multiple first electrode fingers 15 and the second bus bar 14. High-sonic-velocity regions are also formed in the areas where multiple openings 203d are formed in the first bus bar 203, and in the areas where multiple openings 14d are formed in the second bus bar 14.

[0075] In the first embodiment, the central region F, a pair of low-sonic-velocity regions, and a pair of high-sonic-velocity 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 makes it easier to confine the energy of elastic waves within the intersection region A. Furthermore, the transverse standing waves generated in the intersection region A can be converted into vibration modes that are pseudo-free ends at both lateral edges of the intersection region A. Specifically, the lateral edges of the intersection region A are the edge on the side of the first edge region H1 and the edge on the side of the second edge region H2. This allows for the suppression of transverse modes. These are also true in the first comparative example.

[0076] However, in the first comparative example, a large ripple occurs within the stopband in the return loss characteristics. The stopband is the region in which the wavelength of an elastic wave becomes constant due to the confinement of the elastic wave within the periodic structure of the metal grating. Let fu be the upper limit of the stopband, i.e., the highest frequency in the stopband. On the other hand, the lower limit of the stopband, i.e., the lowest frequency in the stopband, coincides with the resonant frequency fr. Specifically, in the first comparative example, a large ripple occurs between the upper limit fu of the stopband and the anti-resonant frequency fa.

[0077] As described above, when the central region F, the low-sonic-velocity region, and the high-sonic-velocity region are arranged in this order, the energy of the elastic waves is easily confined within the intersection region A. However, some elastic waves leak out of the intersection region A. In the first comparative example shown in Figure 4, the first edge region H1, the region where the gap between the multiple second electrode fingers 16 and the first busbar 203 is located, the inner busbar section, and the region where the multiple openings 203d are provided are arranged in this order. Some elastic waves then travel from the region where the gap between the multiple second electrode fingers 16 and the first busbar 203 is located to the inner busbar section and the region where the multiple openings 203d are provided.

[0078] The velocity of sound is low in the inner busbar region. On the other hand, a high-velocity sound region is formed in the region where multiple openings 203d are provided. As a result, elastic waves that leak outside the intersection region A are reflected back towards the intersection region A. The reflected elastic waves are directed towards the second edge region H2 and the second busbar 14. Elastic waves reflected between regions with different velocities of sound are less likely to be reflected on the second edge region H2 side and the second busbar 14 side. Therefore, in the first comparative example, the leakage of elastic waves cannot be sufficiently suppressed. As a result, as shown in Figure 6, a large ripple occurs between the upper end fu of the stopband and the anti-resonance frequency fa.

[0079] In contrast, in the first embodiment, no ripple occurs between the upper limit fu of the stopband and the anti-resonant frequency fa. This is for the following reasons.

[0080] As shown in Figure 3, a plurality of first floating electrodes 11 are provided outside the intersection region A, separated by a first gap region G1. In the first embodiment, the direction in which the first envelope E1 extends and the direction in which the plurality of first electrode fingers 15 and the plurality of second electrode fingers 16 extend intersect but are not orthogonal. Therefore, elastic waves leaking outside the intersection region A reach the region where the plurality of first floating electrodes 11 and the plurality of first electrode fingers 15 are arranged alternately, i.e., the first floating electrode formation region U1. Then, the plurality of first floating electrodes 11 and the plurality of first electrode fingers 15 can reflect the elastic waves leaking outside the intersection region A back towards the intersection region A. This reflection is not a reflection between regions with different sound velocities. Therefore, elastic waves reflected by the plurality of first floating electrodes 11 and the plurality of first electrode fingers 15 are less likely to leak on the second busbar 14 side.

[0081] In addition, a second mass-adding film 8B is provided in the first floating electrode formation region U1. This creates a low-sonic-velocity region in the first floating electrode formation region U1. In the second gap region G2, only the multiple first electrode fingers 15 are provided among the multiple first electrode fingers 15 and multiple second electrode fingers 16. This creates a high-sonic-velocity region in the second gap region G2. The low-sonic-velocity region formed in the first floating electrode formation region U1 and the high-sonic-velocity region formed in the second gap region G2 are arranged in this order. This allows elastic waves that were not reflected by the multiple first floating electrodes 11 and multiple first electrode fingers 15 to be reflected towards the intersection region A.

[0082] However, elastic waves leaking outside the intersection region A reach the first floating electrode formation region U1 before reaching the boundary between the first floating electrode formation region U1 and the second gap region G2. As a result, the elastic waves can be effectively reflected by the multiple first floating electrodes 11 and the multiple first electrode fingers 15. Therefore, elastic waves leaking from the intersection region A towards the first busbar 13 and reflected back to the intersection region A are suitably reflected on the second edge region H2 side and the second busbar 14 side. Thus, leakage of elastic wave energy can be effectively suppressed. In summary, the first embodiment makes it possible to suppress transverse modes and suppress leakage of elastic wave energy simultaneously.

[0083] As in the first embodiment, it is preferable that the direction in which the first envelope E1 extends and the direction in which the plurality of first floating electrodes 11 extend intersect but are not orthogonal. This makes it possible to at least bring the characteristics of elastic wave reflection within the IDT electrode 9 closer to the characteristics of elastic wave reflection in the region where the plurality of first floating electrodes 11 and the plurality of first electrode fingers 15 are alternately arranged. This makes it possible to reflect elastic waves more reliably in that region.

[0084] It is further demonstrated that energy leakage of elastic waves can be suppressed in the first floating electrode formation region U1. The first embodiment was compared with the second comparative example.

[0085] The second comparative example shown in Figure 7 differs from the first embodiment in that the IDT electrode 209B does not have a plurality of floating electrodes but has a plurality of first offset electrodes 207, and in the position where the second mass-adding film 8B is provided. The second comparative example also differs from the first embodiment in that a second gap region is not provided. One end of the plurality of first offset electrodes 207 is connected to the first busbar 13. The other end of the plurality of first offset electrodes 207 faces the tip of the plurality of second electrode fingers 16 across a gap. The second mass-adding film 8B is provided over the plurality of first offset electrodes 207.

[0086] A seismic wave apparatus 10 having the configuration of the first embodiment and a seismic wave apparatus of a second comparative example were prepared, and their impedance frequency characteristics and return loss were compared. The design parameters of the seismic wave apparatus 10 having the configuration of the first embodiment were the same as those used in the comparison shown in Figures 5 and 6.

[0087] Figure 8 shows the impedance frequency characteristics in the first embodiment and the second comparative example. Figure 9 shows the return loss in the first embodiment and the second comparative example.

[0088] As shown in Figure 8, there is no significant difference between the first embodiment and the second comparative example in terms of impedance frequency characteristics. Therefore, the relative bandwidth and capacitance are almost identical in the first embodiment and the second comparative example.

[0089] On the other hand, as shown in Figure 9, in the second comparative example, the loss is large in the bandwidth between the resonant frequency fr and the anti-resonant frequency fa. In addition, a large ripple occurs near the anti-resonant frequency fa in that bandwidth.

[0090] In contrast, in the first embodiment, the loss is small and the ripple is suppressed between the resonant frequency fr and the anti-resonant frequency fa. This is because, in the first embodiment shown in Figure 3, a second gap region G2 is provided, and a high-sonic-velocity region is formed in this region. The low-sonic-velocity region formed in the first floating electrode formation region U1 and the high-sonic-velocity region formed in the second gap region G2 are arranged in this order. As a result, elastic waves leaking from the intersection region A can be reflected back to the intersection region A side. Thus, in the first embodiment, the leakage of elastic wave energy can be suppressed, and the loss can be suppressed. In addition, ripple can be suppressed.

[0091] Furthermore, the first embodiment was compared with the third and fourth comparative examples.

[0092] The third comparative example shown in Figure 10 differs from the first embodiment in that a second mass-adding film is not provided. The fourth comparative example shown in Figure 11 differs from the first embodiment in that a second mass-adding film is not provided and the width of the second gap region G2 is 1λ or more. The width of the second gap region G2 in the third comparative example is the same as the width of the second gap region G2 in the first embodiment.

[0093] A seismic wave apparatus 10 having the configuration of the first embodiment, as well as seismic wave apparatuses of the third and fourth comparative examples, were prepared, and their impedance frequency characteristics and return losses were compared. The design parameters of the seismic wave apparatus 10 having the configuration of the first embodiment were the same as those used in the comparisons shown in Figures 5 and 6.

[0094] Figure 12 shows the impedance frequency characteristics for the first embodiment, the third comparative example, and the fourth comparative example. Figure 13 shows the return loss for the first embodiment, the third comparative example, and the fourth comparative example.

[0095] As shown in Figure 12, the first embodiment, the third comparative example, and the fourth comparative example show no significant difference in impedance frequency characteristics. Therefore, the relative bandwidth and capacitance are almost identical in the first embodiment, the third comparative example, and the fourth comparative example.

[0096] On the other hand, as shown in Figure 13, the third comparative example and the fourth comparative example exhibit significant loss in the bandwidth between the resonant frequency fr and the anti-resonant frequency fa. In addition, large ripple occurs near the anti-resonant frequency fa in this bandwidth. The ripple is particularly large in the fourth comparative example.

[0097] In contrast, in the first embodiment, the loss is small and ripple is suppressed between the resonant frequency fr and the anti-resonant frequency fa. This is because, in the first embodiment shown in Figure 3, a second mass-adding film 8B is provided in the first floating electrode formation region U1, and a low-sonic-velocity region is formed in this region. The low-sonic-velocity region formed in the first floating electrode formation region U1 and the high-sonic-velocity region formed in the second gap region G2 are arranged in this order. As a result, elastic waves leaking from the intersection region A can be reflected back to the intersection region A side. Thus, in the first embodiment, leakage of elastic wave energy can be suppressed, and losses can be suppressed. In addition, ripple can be suppressed.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] In this specification, "one frequency and the other frequency being approximately the same" means that the absolute value of the difference between the two frequencies is 10% 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°.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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 plan view are shapes with a gradually changing curvature. Therefore, in the intersection region A, the curvature of each first electrode finger 15 and second electrode finger 16 is not constant. Specifically, the shapes of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 in 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 plan view may be shapes that can be approximated by elliptical arcs. Alternatively, for example, the shape of each electrode finger in plan view may be a parabola that cannot be approximated by circular arcs or elliptical arcs.

[0108] Curvature is a quantity that represents the degree of curvature of a curve or surface. It can also be expressed as curvature by calculating the radius when a curve is locally approximated as a circular arc at any point on the curve, and then taking the reciprocal of that radius. That is, if the calculated radius is r, then the curvature is 1 / r.

[0109] 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.

[0110] The tip of the electrode finger is defined as the portion extending approximately 1λ from the tip of the electrode finger along the direction in which the electrode finger extends. The adjacent portion is also defined as the portion extending approximately 1λ along the direction in which the electrode finger extends. The first edge region H1 is the region where the tip of the second electrode finger 16 and the adjacent portion of the first electrode finger 15 are located. The second edge region H2 is the region where the tip of the first electrode finger 15 and the adjacent portion of the second electrode finger 16 are located.

[0111] 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.

[0112] 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.

[0113] As an example of the third type, the excitation angle θ in all first electrode fingers 15 and all second electrode fingers 16 C_prop It 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.

[0114] 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.

[0115] 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 curved shapes from each other. Therefore, the relationship shown in Figure 14 below holds.

[0116] Figure 14 is a schematic plan view of the IDT electrode in the first embodiment, showing the circle containing the arc when the shape of the electrode finger in a plan view is approximated as a circular arc. In Figure 14, the IDT electrode 9, reflector 7A, and reflector 7B are shown by schematic diagrams with two diagonals added to the shape showing the outline.

[0117] In Figure 14, 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.

[0118] 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.

[0119] 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 reflector 7A and reflector 7B has the same shape as each electrode finger in IDT electrode 9. Specifically, in reflector 7A and reflector 7B, 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.

[0120] Thus, the shapes of the multiple reflector electrode fingers in reflectors 7A and 7B correspond to the shapes of the multiple electrode fingers in the IDT electrode 9. As a result, the elastic waves can be effectively reflected back to the IDT electrode 9 by reflectors 7A and 7B.

[0121] 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 a circular arc, are different from each other.

[0122] 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, it is preferable that, 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 in the curved region, 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. However, in the curved region, it is sufficient that, when the planar shapes of at least one pair of electrode fingers among the multiple first electrode fingers 15 and multiple second electrode fingers 16 of the IDT electrode 9 are approximated as elliptical arcs, the positions of the centroids of the ellipses containing the elliptical arcs are different from each other.

[0123] 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°.

[0124] In the following, unless otherwise specified, the statement that the resonant frequency or anti-resonant frequency is approximately the same means that the resonant frequency or anti-resonant frequency of the main mode is approximately the same. In the first embodiment, in the crossover 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. More specifically, in the first embodiment, the excitation angle θ C_prop In the region where the same, the duty cycle is constant. In at least a portion of the crossover region A, the excitation angle θ of the IDT electrode 9 is set such that the resonant frequency or anti-resonant frequency is approximately the same. C_prop The duty cycle in the region where the same is the excitation angle θ C_propThe larger the absolute value of [the variable], the larger or smaller it becomes. However, this is not the only possible interpretation.

[0125] For example, the excitation angle θ of the IDT electrode 9 C_prop In the portion where the same, the electrode finger pitch may be constant. In at least a portion of the crossover region A, the excitation angle θ of the IDT electrode 9 is such that the resonant frequency or anti-resonant frequency substantially coincides. C_prop The electrode finger pitch in the portion where the same is the excitation angle θ C_prop The larger the absolute value of , the wider or narrower the range may be.

[0126] Alternatively, the excitation angle θ of the IDT electrode 9 C_prop In the portion where the same, the thickness of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 may be constant. In at least a portion of the intersection region A, the excitation angle θ of the multiple first electrode fingers 15 and the multiple second electrode fingers 16 may be set such that the resonant frequency or anti-resonant frequency substantially coincides. C_prop The thickness may change in the portion where the same angle is maintained. Specifically, the excitation angle θ C_prop The greater the absolute value of , the thicker or thinner the above thickness may be.

[0127] 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 constant in the region where it is the same, and 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.

[0128] 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 19 is provided on the piezoelectric substrate 2 so as to cover the IDT electrode 9, the thickness of the dielectric film 19 is changed in the intersection region A, according to the excitation angle θ. C_prop The parameters of the IDT electrode 9, or multiple parameters other than those of the IDT electrode 9, may be changed in the crossover region A, according to 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.

[0129] 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 ensures that the resonance characteristics of the elastic wave device 10 are improved more reliably.

[0130] As described above, in the first embodiment shown in Figure 3, the width of the second gap region G2 is less than 1λ. However, it is not limited to this. For example, in the first modified example of the first embodiment shown in Figure 15, the width of the second gap region G2 is 1λ or more. In this case, the dimension of the high-sound velocity region formed in the second gap region G2 along the normal direction of the third envelope E3 can be increased. This allows the elastic waves to be more reliably confined to the intersection region A. In addition, similar to the first embodiment, transverse modes can be suppressed, and leakage of elastic wave energy from the second busbar side and other areas can be suppressed.

[0131] Returning to Figure 3, in the first embodiment, the first busbar 13 does not have any openings. The first busbar 13 may be configured similarly to the second busbar 14. For example, in the second modified example of the first embodiment shown in Figure 16, the first busbar 13B of the IDT electrode 9B is provided with a plurality of openings 13d. More specifically, the first busbar 13B has an inner busbar portion 13a and an outer busbar portion 13b, and a plurality of connecting portions 13c. The inner busbar portion 13a and the outer busbar portion 13b face each other. Of the inner busbar portion 13a and the outer busbar portion 13b, the inner busbar portion 13a is located on the side of the intersection region A. The plurality of connecting portions 13c connect the inner busbar portion 13a and the outer busbar portion 13b. Each of the plurality of openings 13d is an opening surrounded by the inner busbar portion 13a, the outer busbar portion 13b, and the plurality of connecting portions 13c.

[0132] The speed of sound in the region of the first busbar 13B where multiple openings 13d are formed is higher than the speed of sound in the intersection region A, similar to the region of the second busbar 14 where multiple openings 14d are formed, as shown with reference to Figure 3. As a result, a high-speed sound region is formed in the region of the first busbar 13B where multiple openings 13d are formed. In this case, elastic waves can be more reliably confined to the intersection region A side. In addition, in this modified example, as in the first embodiment, transverse modes can be suppressed, and leakage of elastic wave energy from the second busbar side and other sides can be suppressed.

[0133] Alternatively, the IDT electrode 9 shown in Figure 3 may have multiple offset electrodes. For example, in the third modified example of the first embodiment shown in Figure 17, the IDT electrode 9C has multiple offset electrodes. Specifically, the multiple offset electrodes of the IDT electrode 9C are a plurality of first offset electrodes 17 and a plurality of second offset electrodes 18. One end of each of the plurality of first offset electrodes 17 is connected to the first busbar 13. The first electrode fingers 15 and the first offset electrodes 17 are arranged alternately.

[0134] One end of each of the multiple second offset electrodes 18 is connected to the second busbar 14C. The second electrode fingers 16 and the second offset electrodes 18 are arranged alternately. The second busbar 14C does not have any openings.

[0135] Similar to the multiple first electrode fingers 15 and the multiple second electrode fingers 16, the multiple first offset electrodes 17 and the multiple second offset electrodes 18 each include a base end and a tip end. The base ends of the first electrode fingers 15 and the first offset electrodes 17 are the portions connected to the first busbar 13. The base ends of the second electrode fingers 16 and the second offset electrodes 18 are the portions connected to the second busbar 14C. The tip end of the first electrode finger 15 and the tip end of the second offset electrode 18 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 17 face each other with a gap between them.

[0136] In this modified example, the plan view shapes of the multiple first offset electrodes 17 are curved. Specifically, the shape of each first offset electrode 17 corresponds to the shape of the opposing second electrode finger 16. More specifically, the plan view shapes of the multiple first offset electrodes 17 are shapes that can be approximated by circular arcs. When the plan view shapes of any first offset electrode 17 and the second electrode finger 16 facing the first offset electrode 17 are approximated by circular arcs, the circle containing each arc is the same circle.

[0137] The curvature of the tips of all the first offset electrodes 17 is 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 17 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 first offset electrodes 17 among the multiple first offset electrodes 17 may be different from each other. In this case as well, the main mode can still be effectively reflected towards the crossover region A.

[0138] Alternatively, for example, the shape of the multiple first offset electrodes 17 in plan view may be linear. In this case, the distance from the tip of the first offset electrode 17 to the first busbar 13 can be shortened. This makes it possible to lower the electrical resistance of the IDT electrode 9C. Therefore, when the elastic wave device is used as a filter device, it is possible to suppress the increase in insertion loss.

[0139] In this modified example, the shape of the multiple second offset electrodes 18 in plan view is linear. As a result, the shape of each second offset electrode 18 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 9C can be reduced.

[0140] Furthermore, in this modified example, similar to the first embodiment, transverse modes can be suppressed, and leakage of elastic wave energy can be reduced.

[0141] The configurations of the first to third modified examples of the first embodiment can also be adopted in other configurations of the present invention. For example, at least the first busbar of the pair of busbars of the IDT electrode may be provided with multiple openings similar to those in the first modified example. Alternatively, in the present invention, each busbar of the IDT electrode may not be provided with multiple openings, and the IDT electrode may not have multiple offset electrodes.

[0142] Returning to Figure 2, the following shows examples of materials for each component in the piezoelectric substrate 2.

[0143] 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.

[0144] 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, 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; or semiconductors such as silicon; or materials mainly composed of the above materials can be used. 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.

[0145] 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.

[0146] The piezoelectric layer 6 shown in Figure 2 may be, for example, a piezoelectric single crystal substrate. The piezoelectric layer 6 may also be formed, for example, by film deposition.

[0147] For example, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate) can be used as the material for the piezoelectric layer 6. It is preferable that lithium tantalate or lithium niobate be 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.

[0148] In the piezoelectric layer 6 of the first embodiment, the direction in which the propagation axis extends is the X-direction direction. However, it is not limited to this. The direction in which the propagation axis extends may be, for example, the 90° X-direction direction, or it may be a direction perpendicular to any of the directions in which the electrode fingers of the IDT electrode 9 extend.

[0149] 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.

[0150] The materials for the IDT electrode 9, reflector 7A, and reflector 7B 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, reflector 7A, and reflector 7B 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, reflector 7A, and reflector 7B.

[0151] 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.

[0152] In the following, the first mass-adding film 8A, the second mass-adding film 8B, the third mass-adding film 8C, and the other mass-adding films may be collectively referred to simply as "mass-adding films." In the first embodiment, the first mass-adding film 8A, the second mass-adding film 8B, and the third mass-adding film 8C are directly provided on the piezoelectric layer 6 and on the first electrode finger 15, the second electrode finger 16, or the first floating electrode 11. Therefore, in the portion where the mass-adding film is laminated with the IDT electrode 9, the piezoelectric layer 6, the IDT electrode 9, and the mass-adding film are laminated in this order. However, in the portion where the mass-adding film is laminated with the IDT electrode 9, the piezoelectric layer 6, the mass-adding film, and the IDT electrode 9 may be laminated in this order. That is, the mass-adding film may be provided between the piezoelectric layer 6 and the IDT electrode 9.

[0153] The dielectric film 19 shown in Figure 2 is provided on the first mass-adding film 8A, the second mass-adding film 8B, and the third mass-adding film 8C. Suitable dielectric materials can be used for the first mass-adding film 8A, the second mass-adding film 8B, and the third mass-adding film 8C.

[0154] However, a first mass-adding film 8A, a second mass-adding film 8B, and a third mass-adding film 8C may be provided on the dielectric film 19. In this case, suitable metals or dielectrics can be used as the materials for the first mass-adding film 8A, the second mass-adding film 8B, and the third mass-adding film 8C. It is preferable that the materials for the first mass-adding film 8A, the second mass-adding film 8B, and the third mass-adding film 8C are the same as the materials for the low-sonic film.

[0155] In the first embodiment, no floating electrodes are provided on the second busbar 14 side. However, multiple floating electrodes may be provided on both the first busbar 13 side and the second busbar 14 side. This example is shown in the second embodiment.

[0156] Figure 18 is a schematic plan view showing an enlarged view of the area around the first and second busbars of the IDT electrode in the second embodiment.

[0157] This embodiment differs from the first embodiment in that the IDT electrode 29 has a plurality of second floating electrodes 22. This embodiment also differs from the first embodiment in that the second busbar 14C does not have a plurality of openings. Furthermore, the second embodiment differs from the first embodiment in that a fourth mass-adding membrane 28D is provided. Apart from the above, the elastic wave apparatus 20 of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment. Hereinafter, the first floating electrode 11 and the second floating electrode 22 may be simply referred to as floating electrodes.

[0158] The multiple second floating electrodes 22 are located between the second edge region H2 and the second busbar 14C. The multiple second floating electrodes 22 are not connected to the first busbar 13, the second busbar 14C, the multiple first electrode fingers 15, and the multiple second electrode fingers 16. The multiple second floating electrodes 22 and the multiple second electrode fingers 16 are arranged alternately. The region located between the second edge region H2 and the second busbar 14C, where the multiple second floating electrodes 22 are provided, is the second floating electrode forming region U2.

[0159] More specifically, the second floating electrode formation region U2 is a band-shaped region in which a plurality of second floating electrodes 22 and a plurality of second electrode fingers 16 are arranged alternately. The second floating electrode formation region U2 shall include the entire thickness of the elastic wave apparatus 20.

[0160] The fourth mass-adding film 28D is provided in the second floating electrode formation region U2. This constitutes a low-sonic region in the second floating electrode formation region U2. Specifically, the fourth mass-adding film 28D has a strip-like shape. The fourth mass-adding film 28D is continuously provided over a plurality of second floating electrodes 22 and a plurality of second electrode fingers 16. Therefore, the fourth mass-adding film 28D is also provided on the piezoelectric layer 6 in the portion between the second floating electrodes 22 and the second electrode fingers 16.

[0161] As the material for the fourth mass-adding membrane 28D, it is preferable to use the same material as the low-sonic membrane described above, similar to the first mass-adding membrane 8A, the second mass-adding membrane 8B, and the third mass-adding membrane 8C.

[0162] The shape of the multiple second floating electrodes 22 in a plan view is linear. However, the shape of the multiple second floating electrodes 22 in a plan view may also be curved.

[0163] The tips of the multiple first electrode fingers 15 face one end of the multiple second floating electrodes 22, separated by a gap. The region where the gap between the multiple first electrode fingers 15 and the multiple second floating electrodes 22 is located is the third gap region G3. The other ends of the multiple second floating electrodes 22 face the second busbar 14C, separated by a gap. The region where the gap between the multiple second floating electrodes 22 and the second busbar 14C is located is the fourth gap region G4.

[0164] The ends of the multiple second floating electrodes 22 on the second busbar 14C side are considered to be the tips of the multiple second floating electrodes 22. Each of the tips of the multiple second floating electrodes 22 includes its tip. The imaginary line formed by connecting the tips of the multiple second floating electrodes 22 is called the fourth envelope E4. In this case, the region between the fourth envelope E4 and the second busbar 14C is the fourth gap region G4.

[0165] The direction in which the fourth envelope E4 extends is perpendicular to the direction in which the multiple second floating electrodes 22 extend. Similarly, the direction in which the second envelope E2 extends is perpendicular to the direction in which the multiple second floating electrodes 22 extend.

[0166] In this embodiment, when the width of the third gap region G3 is defined as the dimension of the third gap region G3 along the normal direction of the fourth envelope E4, the width of the third gap region G3 is less than 1λ. In this embodiment, when the width of the fourth gap region G4 is defined as the dimension of the fourth gap region G4 along the normal direction of the fourth envelope E4, the width of the fourth gap region G4 is less than 1λ. However, the widths of the third gap region G3 and the fourth gap region G4 are not limited to the above.

[0167] In this embodiment, energy leakage of elastic waves can be effectively suppressed on both the first busbar 13 side and the second busbar 14C side. In addition, transverse modes can be suppressed, similar to the first embodiment.

[0168] The shape of each mass-adding film in the elastic wave apparatus 20 in a plan view is strip-shaped. However, it is not limited to this. Below, the first to third modifications of the second embodiment are shown, in which only the shape or arrangement of any one of the mass-adding films differs from that of the second embodiment. In the first to third modifications, as in the second embodiment, transverse modes can be suppressed and leakage of elastic wave energy can be suppressed.

[0169] In the first modified example shown in Figure 19, a plurality of second mass-adding films 8B are provided in the first floating electrode formation region U1. The plurality of second mass-adding films 8B have a piece-like shape. Specifically, a second mass-adding film 8B is provided on each first electrode finger 15 and on each second electrode finger 16. More specifically, each second mass-adding film 8B is provided across one electrode finger and the piezoelectric layer 6. Each second mass-adding film 8B is in contact with only one of two adjacent electrode fingers.

[0170] Similarly, multiple fourth mass-adding films 28D are provided in the second floating electrode formation region U2. Each fourth mass-adding film 28D is provided across one electrode finger and the piezoelectric layer 6. Each fourth mass-adding film 28D is in contact with only one of two adjacent electrode fingers. Alternatively, multiple second mass-adding films 8B and multiple fourth mass-adding films 28D may each be provided on only one electrode finger.

[0171] In this modified example, the materials for the multiple second mass-adding films 8B and the multiple fourth mass-adding films 28D can be any suitable metal or dielectric material.

[0172] On the other hand, similar to the second embodiment, one first mass-adding film 8A is provided in the first edge region H1. One third mass-adding film 8C is provided in the second edge region H2. The first mass-adding film 8A and the third mass-adding film 8C have a strip-like shape in plan view. In this modified example as well, low-sonic regions are formed in the first edge region H1, the first floating electrode formation region U1, the second edge region H2, and the second floating electrode formation region U2, respectively.

[0173] In the second modified example shown in Figure 20, a plurality of first mass-adding films 8A are provided on the first edge region H1. The plurality of first mass-adding films 8A have a piece-like shape. Specifically, a first mass-adding film 8A is provided on each first electrode finger 15 and each second electrode finger 16. More specifically, each first mass-adding film 8A is provided across one electrode finger and the piezoelectric layer 6. Each first mass-adding film 8A is in contact with only one of two adjacent electrode fingers.

[0174] Similarly, multiple third mass-adding films 8C are provided in the second edge region H2. Each third mass-adding film 8C is provided across one electrode finger and the piezoelectric layer 6. Each third mass-adding film 8C is in contact with only one of two adjacent electrode fingers. Alternatively, multiple first mass-adding films 8A and multiple third mass-adding films 8C may each be provided on only one electrode finger.

[0175] In this modified example, the materials for the multiple first mass-adding films 8A and the multiple third mass-adding films 8C can be any suitable metal or dielectric material.

[0176] In addition, similar to the first modified example, the first floating electrode formation region U1 is provided with a plurality of second mass-adding films 8B. The second floating electrode formation region U2 is provided with a plurality of fourth mass-adding films 28D. Each second mass-adding film 8B and each fourth mass-adding film 28D has a piece-like shape. In this modified example as well, low-sonic regions are formed in the first edge region H1, the first floating electrode formation region U1, the second edge region H2, and the second floating electrode formation region U2, respectively.

[0177] In the third modified example shown in Figure 21, a plurality of first mass-adding films 8A are provided in the first edge region H1. The plurality of first mass-adding films 8A have a piece-like shape. Specifically, the plurality of first mass-adding films 8A are provided in the portion between the electrode fingers on the piezoelectric layer 6. Each first mass-adding film 8A does not come into contact with the electrode finger.

[0178] Multiple second mass-adding films 8B are also provided in the first floating electrode formation region U1. Each second mass-adding film 8B is provided in the portion between the first floating electrode 11 and the first electrode finger 15 on the piezoelectric layer 6. Multiple third mass-adding films 8C are also provided in the second edge region H2. Each third mass-adding film 8C is provided in the portion between the electrode fingers on the piezoelectric layer 6. Similarly, multiple fourth mass-adding films 28D are also provided in the second floating electrode formation region U2. Each fourth mass-adding film 28D is provided in the portion between the second floating electrode 22 and the second electrode finger 16 on the piezoelectric layer 6. Each second mass-adding film 8B, each third mass-adding film 8C, and each fourth mass-adding film 28D do not come into contact with the electrode fingers or the floating electrode.

[0179] In this modified example, the materials for the multiple first mass-adding films 8A, multiple second mass-adding films 8B, multiple third mass-adding films 8C, and multiple fourth mass-adding films 28D can be any suitable metal or dielectric material. Each first mass-adding film 8A and each third mass-adding film 8C may be in contact with both of two adjacent electrode fingers. Each second mass-adding film 8B and each fourth mass-adding film 28D may be in contact with both adjacent electrode fingers and floating electrodes. In these cases, the materials for the multiple first mass-adding films 8A, multiple second mass-adding films 8B, multiple third mass-adding films 8C, and multiple fourth mass-adding films 28D can be any suitable dielectric material.

[0180] In this modified example, low-sonic-velocity regions are also formed in the first edge region H1, the first floating electrode formation region U1, the second edge region H2, and the second floating electrode formation region U2, respectively.

[0181] While some examples were given in the first to third modifications, the combinations of arrangement of the mass-adding films may be other than those shown in the first to third modifications.

[0182] Although omitted in Figure 18, the elastic wave apparatus 20 has a dielectric film 19, as shown with reference to Figure 2. The thickness of the dielectric film 19 is thinner than the thickness of the IDT electrode 29. However, the IDT electrode 29 may be embedded in a protective film. This example is shown in the third embodiment.

[0183] Figure 22 is a schematic front cross-sectional view showing a portion of the elastic wave apparatus according to the third embodiment, passing through the first edge region.

[0184] This embodiment differs from the second embodiment in that the IDT electrode 29 has a protective film 39 instead of the dielectric film 19 shown with reference to Figure 2. Apart from the above, the elastic wave apparatus 30 of this embodiment has the same configuration as the elastic wave apparatus 20 of the second embodiment.

[0185] Specifically, a protective film 39 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 29. The thickness of the protective film 39 is greater than the thickness of the IDT electrode 29. The IDT electrode 29 is embedded in the protective film 39. This makes the IDT electrode 29 less susceptible to damage. In addition, in this embodiment as well, similar to the second embodiment, transverse modes can be suppressed, and leakage of elastic wave energy can be suppressed.

[0186] The protective film 39 is a single layer film. However, the protective film 39 may be a laminate. For example, in the modified example of the third embodiment shown in Figure 23, the protective film 39A has a first protective layer 39a and a second protective layer 39b. The IDT electrode 29 is embedded in the first protective layer 39a. The second protective layer 39b is provided on the first protective layer 39a. As a result, multiple effects can be obtained with the protective film 39A.

[0187] Specifically, in this modified example, silicon oxide is used as the material for the first protective layer 39a. This makes it possible to reduce the absolute value of the frequency temperature coefficient (TCF) in the elastic wave apparatus. Therefore, the temperature characteristics of the elastic wave apparatus can be improved. Silicon nitride is used for the second protective layer 39b. This makes it possible to improve the moisture resistance of the elastic wave apparatus. However, the materials for the first protective layer 39a and the second protective layer 39b are not limited to those described above. The protective film 39A may be a laminate of three or more layers.

[0188] In this modified example, as in the third embodiment, transverse modes can be suppressed, and leakage of elastic wave energy can be reduced.

[0189] In the first to third embodiments and their respective modifications, each mass-adding film is provided directly on the piezoelectric layer or the IDT electrode. However, the arrangement of each mass-adding film is not limited to the above. This example is shown in the fourth embodiment.

[0190] Figure 24 is a schematic front cross-sectional view showing a portion of the elastic wave apparatus according to the fourth embodiment, passing through the first edge region.

[0191] This embodiment differs from the third embodiment in the arrangement of each mass-adding film. Apart from the above, the elastic wave apparatus 40 of this embodiment has the same configuration as the elastic wave apparatus 30 of the third embodiment.

[0192] In the elastic wave apparatus 40, the first mass-adding film 8A is provided within the piezoelectric substrate 2. Specifically, one first mass-adding film 8A is provided within the piezoelectric layer 6 and one within the second layer 5b of the intermediate layer 5. In addition, one first mass-adding film 8A is provided within the protective film 39 and one on the protective film 39.

[0193] Similarly, the second, third, and fourth mass-adding films are each provided one within the piezoelectric layer 6, one within the second layer 5b of the intermediate layer 5, one within the protective film 39, and one on the protective film 39. In this embodiment as well, similar to the third embodiment, low-sonic regions are configured in the first edge region, the first floating electrode formation region, the second edge region, and the second floating electrode formation region, respectively. In the elastic wave device 40, transverse modes can be suppressed, and leakage of elastic wave energy can be suppressed.

[0194] In this embodiment, the shape of each mass-adding film in plan view is a strip shape. However, at least one of the first mass-adding film 8A, the second mass-adding film, the third mass-adding film, and the fourth mass-adding film may be arranged in the same manner as the first to third modified examples of the second embodiment shown in Figures 19 to 21. Alternatively, the combination of arrangements of the mass-adding films may be other than the combinations of the first to third modified examples.

[0195] The first mass-adding film 8A may be provided in at least one of the following locations: inside the piezoelectric substrate 2, on the piezoelectric layer 6, on the electrode finger, inside the protective film 39, and on the protective film 39. The same applies to the third mass-adding film. The second mass-adding film may be provided in at least one of the following locations: inside the piezoelectric substrate 2, on the piezoelectric layer 6, on the first floating electrode, on the first electrode finger 15, inside the protective film 39, and on the protective film 39. The fourth mass-adding film may be provided in at least one of the following locations: inside the piezoelectric substrate 2, on the piezoelectric layer 6, on the second floating electrode, on the second electrode finger 16, inside the protective film 39, and on the protective film 39.

[0196] In the first to fourth embodiments and their respective modifications, the low-sonic region is provided by a mass-adding membrane. However, the low-sonic region may also be provided by widening the width of the electrode fingers or floating electrodes. This example is shown in the fifth embodiment.

[0197] Figure 25 is a schematic plan view showing an enlarged view of the area around the first and second busbars of the IDT electrode in the fifth embodiment.

[0198] This embodiment differs from the second embodiment in that a mass-adding film is not provided, and the electrode fingers and floating electrodes of the IDT electrode 59 have wide portions. The width of the electrode fingers in the wide portion is wider than the width of the electrode fingers in the central region F. The width of the floating electrode in the wide portion is wider than the width of the floating electrode in the portion other than the wide portion. Except for the above, the elastic wave apparatus of this embodiment has the same configuration as the elastic wave apparatus 20 of the second embodiment.

[0199] Specifically, in the first edge region H1, the plurality of second electrode fingers 56 have a first wide portion 56a that is wider than the width in the central region F. This constitutes a low-sonic region in the first edge region H1. In this embodiment, the plurality of first electrode fingers 55 in the first edge region H1 do not have a first wide portion. However, the plurality of first electrode fingers 55 in the first edge region H1 may have a first wide portion.

[0200] In addition, in the first floating electrode formation region U1, the plurality of first floating electrodes 51 have a second wide portion 51a that is wider than the width in other parts. This constitutes a low-sonic region in the first floating electrode formation region U1. In this embodiment, the plurality of first electrode fingers 55 in the first floating electrode formation region U1 do not have a second wide portion. However, the plurality of first electrode fingers 55 in the first floating electrode formation region U1 may have a second wide portion.

[0201] On the other hand, in the second edge region H2, the multiple first electrode fingers 55 have a third wide portion 55b that is wider than the width in the central region F. This constitutes a low-sonic region in the second edge region H2. In this embodiment, the multiple second electrode fingers 56 in the second edge region H2 do not have a third wide portion. However, the multiple second electrode fingers 56 in the second edge region H2 may have a third wide portion.

[0202] Furthermore, in the second floating electrode formation region U2, the plurality of second floating electrodes 52 have a fourth wide portion 52b that is wider than the width in other parts. This constitutes a low-sonic region in the second floating electrode formation region U2. In this embodiment, the plurality of second electrode fingers 56 in the second floating electrode formation region U2 do not have a fourth wide portion. However, the plurality of second electrode fingers 56 in the second floating electrode formation region U2 may have a fourth wide portion.

[0203] The features of this embodiment are as follows: 1) In the first edge region H1, at least one of the plurality of first electrode fingers 55 and the plurality of second electrode fingers 56 has a first wide portion that is wider than the width in the central region F. 2) In the first floating electrode formation region U1, at least one of the following configurations is achieved: the plurality of first electrode fingers 55 have a second wide portion that is wider than the width in the central region F, and the plurality of first floating electrodes 51 have a second wide portion 51a that is wider than the other portions. As a result, a low-sonic region is formed in the first edge region H1 and the first floating electrode formation region U1. In this case as well, as in the first and second embodiments, transverse modes can be suppressed and leakage of elastic wave energy can be suppressed.

[0204] As in this embodiment, it is preferable to have the following configuration: 3) In the second edge region H2, at least one of the plurality of first electrode fingers 55 and the plurality of second electrode fingers 56 has a third wide portion that is wider than the width in the central region F. 4) In the second floating electrode forming region U2, at least one of the following configurations is available: a plurality of second electrode fingers 56 having a fourth wide portion that is wider than the width in the central region F, and a plurality of second floating electrodes 52 having a fourth wide portion 52b that is wider than the other portions. By having the above configuration 3) or 4) in the elastic wave device, transverse modes can be effectively suppressed and leakage of elastic wave energy can be effectively suppressed.

[0205] However, even when the electrode finger or floating electrode has a wide portion, a mass-adding film may be provided. This example is shown by a first and second modification of the fifth embodiment, which differ from the fifth embodiment only in that a mass-adding film is provided and the arrangement of the wide portion is arranged. In the first and second modifications, as in the fifth embodiment, transverse modes can be suppressed and leakage of elastic wave energy can be suppressed.

[0206] In the first modified example shown in Figure 26, a first mass-adding film 8A is provided in the first edge region H1. A third mass-adding film 8C is provided in the second edge region H2. On the other hand, the first floating electrode formation region U1 and the second floating electrode formation region U2 are configured in the same manner as in the fifth embodiment.

[0207] Furthermore, the elastic wave device only needs to have the configuration of 2) above in the first floating electrode formation region U1. That is, in this region, it is sufficient to have at least one of the following configurations: a configuration in which a plurality of first electrode fingers 55 have a second wide portion that is wider than the width in the central region F, and a configuration in which a plurality of first floating electrodes 51 have a second wide portion 51a that is wider than the other parts. The second floating electrode formation region U2 only needs to have the configuration of 4) above. That is, in this region, it is sufficient to have at least one of the following configurations: a configuration in which a plurality of second electrode fingers 56 have a fourth wide portion that is wider than the width in the central region F, and a configuration in which a plurality of second floating electrodes 52 have a fourth wide portion 52b that is wider than the other parts.

[0208] In the second modified example shown in Figure 27, a second mass-adding film 8B is provided in the first floating electrode formation region U1. A fourth mass-adding film 28D is provided in the second floating electrode formation region U2. On the other hand, the first edge region H1 and the second edge region H2 are configured in the same manner as in the fifth embodiment.

[0209] Furthermore, the elastic wave device only needs to have the configuration of 1) above in the first edge region H1. That is, in this region, at least one of the plurality of first electrode fingers 55 and the plurality of second electrode fingers 56 has a first wide portion that is wider than the width in the central region F. The device only needs to have the configuration of 3) above in the second edge region H2. That is, in this region, at least one of the plurality of first electrode fingers 55 and the plurality of second electrode fingers 56 has a third wide portion that is wider than the width in the central region F.

[0210] Alternatively, in the region where the mass-adding film is provided, the electrode finger or floating electrode may have a wide portion. This may create a low-sonic-velocity region.

[0211] By the way, in the IDT electrodes of the first to fifth embodiments and each of their modifications, 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.

[0212] 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.

[0213] 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.

[0214] It is preferable that the shapes of the multiple reflector electrode fingers of each reflector 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, each reflector can effectively reflect elastic waves towards the IDT electrode.

[0215] In addition, in the present invention, the shape of the multiple electrode fingers in a plan view may include both curved and straight portions. Examples of this are shown in the sixth and seventh embodiments.

[0216] Figure 28 is a schematic plan view of the elastic wave apparatus according to the sixth embodiment.

[0217] This embodiment differs from the second embodiment in the shape of the multiple electrode fingers of the IDT electrode 69. The shape of the multiple reflector electrode fingers of reflectors 67A and 67B in plan view also corresponds to the shape of the multiple electrode fingers in plan view. This embodiment also differs from the second embodiment in the point where the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends intersect. Apart from the above, the elastic wave apparatus of this embodiment has the same configuration as the elastic wave apparatus 20 of the second embodiment.

[0218] The intersection region A of the IDT electrode 69 has a first curved region W1, a second curved region W2, and a straight region T. As described above, a curved region is a region in which the shapes of the multiple first electrode fingers 65 and the multiple second electrode fingers 66 in a plan view are curved. Note that the intersection region A may include three or more curved regions.

[0219] On the other hand, the linear region T is the region in which the shapes of the multiple first electrode fingers 65 and the multiple second electrode fingers 66 in a plan view are linear. The first curved region W1, the second curved region W2, and the linear region T are aligned in directions where the first busbar 13 and the second busbar 14C face each other. More specifically, the first curved region W1 and the second curved region W2 face each other with the linear region T in between.

[0220] 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 straight region T. 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 second curved region W2 and the straight region T.

[0221] In the IDT electrode 69, each electrode finger has two inflection points. In this specification, each inflection point is the point where a curved portion and a straight portion are connected. The area where the inflection points of multiple electrode fingers are aligned is the boundary between the curved region and the straight region.

[0222] In Figure 28, the dashed line N passes through the center of the intersection region A and extends parallel to the direction in which the propagation axis extends. More specifically, the dashed line N passes through the center of the linear region T. The first envelope E1 is inclined in the positive direction with respect to the direction in which the propagation axis extends. The second envelope E2 is inclined in the negative direction with respect to the direction in which the propagation axis extends.

[0223] In this embodiment, in each of the first curve region W1 and the second curve region W2, the excitation angle θ C_propHowever, the resonant or anti-resonant frequencies are approximately the same throughout the entirety of the first curve region W1 and the second curve region W2. Furthermore, the resonant or anti-resonant frequencies are also approximately the same throughout the entirety of the crossover region A. As a result, unwanted out-of-band waves such as Rayleigh waves can be suppressed by dispersing them.

[0224] In the linear region T, the excitation angle θ C_prop It is constant. More specifically, in the linear region T, the excitation angle θ C_prop θ is 0°. In other words, in this embodiment, in the entire linear region T, the direction in which the multiple electrode fingers extend is perpendicular to the direction in which the propagation axis extends. Therefore, the linear region T is a stable region with respect to the propagation axis. Because the intersection region A has the linear region T, the change in the propagation direction of the IDT electrode 69 as a whole can be reduced, and the propagation of elastic waves can be stabilized. Note that the excitation angle θ in the linear region T is C_prop It does not necessarily have to be 0°.

[0225] In this embodiment, the first curved region W1 includes the first edge region H1. The first floating electrode formation region U1 is formed between the first edge region H1 and the first bus bar 13. Furthermore, a first gap region is positioned between the first edge region H1 and the first floating electrode formation region U1. A second gap region is positioned between the first floating electrode formation region U1 and the first bus bar 13.

[0226] On the other hand, the second curved region W2 includes the second edge region H2. A second floating electrode formation region U2 is formed between the second edge region H2 and the second bus bar 14C. A third gap region is located between the second edge region H2 and the second floating electrode formation region U2. A fourth gap region is located between the second floating electrode formation region U2 and the second bus bar 14C.

[0227] A mass-adding film is provided in the first edge region H1, the second edge region H2, the first floating electrode formation region U1, and the second floating electrode formation region U2, respectively, similar to the second embodiment. As a result, low-sonic regions are formed in the first edge region H1, the second edge region H2, the first floating electrode formation region U1, and the second floating electrode formation region U2, respectively. This allows for the suppression of transverse modes and the reduction of elastic wave energy leakage in this embodiment as well.

[0228] In the first to sixth embodiments and each of their modifications, the curves in the shape of the multiple electrode fingers when viewed from above are smooth curves. However, the curves in the shape of the multiple electrode fingers when viewed from above may be formed by connecting minute straight lines. The curves in the shape of the multiple electrode fingers when viewed from above may be formed by connecting multiple vertices with curves. Alternatively, the curves in the shape of the multiple electrode fingers when viewed from above do not necessarily have to be smooth curves. This example is shown as a modification of the sixth embodiment.

[0229] In the modified example shown in Figure 29, the curves of the IDT electrode 69A when viewed from above are not smooth curves. Specifically, the shape of each first electrode finger 65A when viewed from above is formed by connecting straight lines. These straight lines are not minute in size. More specifically, the length of the straight lines in this shape is, for example, only a few percent of the total length of the first electrode finger 65A. However, the angles between the connected straight lines in this shape are large, for example, between 160° and 180°. Therefore, the shape of each first electrode finger 65A when viewed from above is a shape that can be approximated as a curve. The same applies to the second electrode finger 66A.

[0230] In this modified example, as in the sixth embodiment, transverse modes can be suppressed, and leakage of elastic wave energy can be reduced.

[0231] Figure 30 is a schematic plan view showing an enlarged view of the area around the first and second busbars of the IDT electrode in the seventh embodiment.

[0232] This embodiment differs from the first embodiment in the shape of the multiple electrode fingers of the IDT electrode 79 and the arrangement of the curved regions. The shape of the multiple reflector electrode fingers of each reflector in a plan view also corresponds to the shape of the multiple electrode fingers in a plan view. Except for the points mentioned above, the elastic wave device 70 of this embodiment has the same configuration as the elastic wave device 10 of the first embodiment.

[0233] The intersection region A in the elastic wave apparatus 70 has a curved region W, a first straight region T1, and a second straight region T2. ​​The curved region W, the first straight region T1, and the second straight region T2 are aligned in directions in which the first busbar 13 and the second busbar 14 face each other. More specifically, the first straight region T1 and the second straight region T2 face each other with the curved region W in between. The first straight region T1 includes a part of the central region F and the first edge region H1 in the intersection region A. The second straight region T2 includes a part of the central region F and the second edge region H2. The curved region W is included in the central region F.

[0234] One edge of the curved region W is the boundary between the curved region W and the first straight region T1. This edge is the first intersection line D1. The first intersection line D1 is a hypothetical line that extends parallel to the first envelope E1 and passes through the central region F in the intersection region A.

[0235] The other edge of the curved region W is the boundary between the curved region W and the second straight region T2. ​​This edge is the second intersection line D2. The second intersection line D2 is a hypothetical line that extends parallel to the second envelope E2 and passes through the central region F.

[0236] In each of the first electrode fingers 75, the portion intersecting with the first cross line D1 is the first intersection portion 75c. In each of the second electrode fingers 76, the portion intersecting with the first cross line D1 is the second intersection portion 76c. On the other hand, in each of the first electrode fingers 75, the portion intersecting with the second cross line D2 is the first intersection portion 75d. In each of the second electrode fingers 76, the portion intersecting with the second cross line D2 is the second intersection portion 76d.

[0237] It is assumed that the first intersection portion 75c is a portion located within the curved region W and is a portion within a range of about 1λ along the direction in which the first electrode finger 75 extends from the first cross line D1. Similarly, it is assumed that the second intersection portion 76c is a portion located within the curved region W and is a portion within a range of about 1λ along the direction in which the second electrode finger 76 extends from the first cross line D1. On the other hand, it is assumed that the first intersection portion 75d is a portion located within the curved region W and is a portion within a range of about 1λ along the direction in which the first electrode finger 75 extends from the second cross line D2. It is assumed that the second intersection portion 76d is a portion located within the curved region W and is a portion within a range of about 1λ along the direction in which the second electrode finger 76 extends from the second cross line D2.

[0238] In the curved region W, the excitation angle θ C_prop is not uniform. However, in the entire curved region W, the resonance frequency or the anti-resonance frequency is substantially the same. Furthermore, as a whole of the intersection region A, the resonance frequency or the anti-resonance frequency is substantially the same. Thereby, unnecessary waves outside the band such as Rayleigh waves can be suppressed by dispersing them.

[0239] In this embodiment, in the curved region W, the curvatures of the respective first electrode fingers 75 and second electrode fingers 76 are not constant. And in this embodiment, between the first crossing portions 75c and the second crossing portions 76c of all the first electrode fingers 75 and all the second electrode fingers 76, the curvatures are different from each other. In this case, in the curved region W, in plan view, the shapes of all the electrode fingers of the IDT electrode 79 are curves with different shapes from each other. Thus, similarly to the first embodiment, unnecessary waves can be more surely and effectively suppressed.

[0240] In addition, in this embodiment, between the first crossing portions 75d and the second crossing portions 76d of all the first electrode fingers 75 and all the second electrode fingers 76, the curvatures are different from each other. Also in this case, in the curved region W, in plan view, the shapes of all the electrode fingers of the IDT electrode 79 are curves with different shapes from each other. With this configuration as well, unnecessary waves can be more surely and effectively suppressed.

[0241] However, it is only necessary that the curvatures be different from each other between the first crossing portions 75c and the second crossing portions 76c in at least one set of electrode fingers among the plurality of first electrode fingers 75 and the plurality of second electrode fingers 76. Alternatively, it is only necessary that the curvatures be different from each other between the first crossing portions 75d and the second crossing portions 76d in at least one set of electrode fingers among the plurality of first electrode fingers 75 and the plurality of second electrode fingers 76.

[0242] In other words, when the first crossing line D1 or the second crossing line D2 is used as the crossing line, it is only necessary that the first crossing portion and the second crossing portion based on the crossing line have the above configuration. Specifically, in each first electrode finger 75, the portion crossing the crossing line is the first crossing portion. In each second electrode finger 76, the portion crossing the crossing line is the second crossing portion. And in the curved region W, it is only necessary that the curvatures be different from each other between the first crossing portion and the second crossing portion in at least one set of electrode fingers among the plurality of first electrode fingers 75 and the plurality of second electrode fingers 76.

[0243] In the curve region W of the elastic wave apparatus 70, the shapes of all electrode fingers in plan view are shapes that can be approximated by circular arcs, and are different curve shapes from each other. Therefore, the relationship shown in Figure 14 above holds true in the curve region W. More specifically, in the curve region W, when the shapes of all first electrode fingers 75 and all second electrode fingers 76 in plan view are approximated by circular arcs, the positions of the centers of the circles containing these arcs are different from each other.

[0244] A mass-adding film is provided in the first edge region H1, the second edge region H2, and the first floating electrode formation region U1, respectively, as in the first embodiment. As a result, low-sonic-velocity regions are formed in the first edge region H1, the second edge region H2, and the first floating electrode formation region U1, respectively. This allows for the suppression of transverse modes and the reduction of elastic wave energy leakage in this embodiment as well.

[0245] Furthermore, as in the fifth embodiment, a low-sonic-velocity region may be formed by providing a wide portion. Alternatively, as in each of the modifications of the fifth embodiment, a low-sonic-velocity region may be formed by providing a mass-adding membrane and a wide portion.

[0246] Excitation angle θ in this embodiment C_prop The portion where the angle is 0° is the portion on the second envelope E2. In any part of the intersection region A, the excitation angle θ C_prop It is greater than or equal to 0°. However, in the intersection region A, the excitation angle θ C_prop It may include a portion where the value is less than 0°.

[0247] Excitation angle θ of IDT electrode 79 C_prop Where the same parameters are present, both the electrode finger pitch and duty cycle are constant. However, this is not limited to this. 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. This makes it possible to more reliably improve the resonance characteristics of the elastic wave device 70.

[0248] As described above, in cross region A, the excitation direction of the elastic wave at any part of any electrode finger among the multiple electrode fingers is one of the first to third directions. In this embodiment, the excitation direction is the first direction. Specifically, the first direction as the excitation direction of the elastic wave at any part of any electrode finger is the direction perpendicular to the direction in which the electrode finger extends. The excitation direction may also be the second direction or the third direction.

[0249] In the IDT electrode 79, the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends are parallel. However, as in the sixth embodiment, for example, the direction in which the first envelope E1 extends and the direction in which the second envelope E2 extends may intersect.

[0250] Furthermore, in the present invention, multiple electrode fingers or multiple reflector electrode fingers may have a bent shape at multiple nodes. An example of this is shown in the eighth embodiment.

[0251] Figure 31 is a schematic plan view of an elastic wave apparatus according to the eighth embodiment.

[0252] This embodiment differs from the second embodiment in the shape of the multiple electrode fingers of the IDT electrode 89. The shape of the multiple reflector electrode fingers of the reflector 87A and reflector 87B in plan view also corresponds to the shape of the multiple electrode fingers in plan view. This embodiment also differs from the second embodiment in the shape of the first busbar 83 and the second busbar 84, as well as the shapes of the first envelope E81, the second envelope E82, the third envelope E83, and the fourth envelope E84. Except for the points mentioned above, the elastic wave device 80 of this embodiment has the same configuration as the elastic wave device 20 of the second embodiment.

[0253] In the IDT electrode 89, the plan view shape of the multiple first electrode fingers 85 and the multiple second electrode fingers 86 is a bent shape at multiple nodes. More specifically, the plan view shape of the multiple first electrode fingers 85 and the multiple second electrode fingers 86 is a shape in which straight lines are connected at each node. The plan view shape of the multiple first floating electrodes 81 and the multiple second floating electrodes 82 is a bent shape at one or more nodes.

[0254] In this embodiment, each electrode finger and each floating electrode is bent so as a whole that it is convex toward the reflector 87B. The shape of each electrode finger and each floating electrode in plan view can be approximated as a circular arc, an elliptical arc, or a parabola.

[0255] Figure 32 is a schematic plan view showing the parallel and non-parallel regions in the eighth embodiment. In Figure 32, each region is indicated by hatching. The same hatching and reference numerals are used for the parallel region and the region extended from the parallel region, which will be described later. The same hatching and reference numerals are used for the non-parallel region and the region extended from the non-parallel region, which will be described later.

[0256] Intersecting region A has multiple parallel regions J and multiple non-parallel regions K. Similarly, the first floating electrode formation region U1 and the second floating electrode formation region U2 each have one or more parallel regions J and non-parallel regions K. Specifically, a parallel region J is a region where multiple first electrode fingers 85 and multiple second electrode fingers 86 extend in parallel. A parallel region J is also a region where multiple first floating electrodes 81 and multiple second floating electrodes 82 extend in parallel. A non-parallel region K is a region where the directions in which multiple first electrode fingers 85 and multiple second electrode fingers 86 extend intersect each other. A non-parallel region K is also a region where the directions in which multiple first floating electrodes 81 and multiple second floating electrodes 82 extend intersect each other.

[0257] Furthermore, the intersection region A only needs to include at least two parallel regions J and at least one non-parallel region K. The first floating electrode formation region U1 and the second floating electrode formation region U2 do not necessarily need to have both parallel regions J and non-parallel regions K.

[0258] Parallel regions J and non-parallel regions K are arranged alternately. Multiple first electrode fingers 85 and multiple second electrode fingers 86 each extend linearly in parallel regions J and non-parallel regions K, and are bent at the boundary between parallel regions J and non-parallel regions K. In this embodiment, parallel regions J and non-parallel regions K are arranged alternately throughout the entire intersection region A. However, it is sufficient if parallel regions J and non-parallel regions K are arranged alternately in at least a part of intersection region A.

[0259] In multiple parallel regions J, the directions in which multiple electrode fingers extend are different from each other. Therefore, in the intersecting region A, the excitation direction and excitation angle θ of the elastic wave are different. C_prop These frequencies are not uniform. Furthermore, in this embodiment, the resonant frequency or anti-resonant frequency is approximately the same throughout the entire intersection region A. This allows for the suppression of unwanted out-of-band waves, such as Rayleigh waves, by dispersing them.

[0260] In addition, some of the multiple floating electrodes and some of the electrode fingers are contained within the same parallel region J, while other parts of the multiple floating electrodes and other parts of the electrode fingers are contained within the same non-parallel region K. This allows the multiple floating electrodes to effectively reflect elastic waves, thereby effectively suppressing elastic wave leakage.

[0261] In a plan view, the shapes of the plurality of reflector electrode fingers of reflector 87A and reflector 87B are bent shapes in a plurality of nodes, similar to each electrode finger of the IDT electrode 89. Specifically, the plurality of reflector electrode fingers extend linearly in a region extending the parallel region J and a region extending the non-parallel region K. And the plurality of reflector electrode fingers are bent at the boundary between the region extending the parallel region J and the region extending the non-parallel region K. Thereby, the resonance characteristics can be more surely enhanced.

[0262] As shown in FIG. 31, the first envelope E81 has a plurality of portions inclined with respect to the propagation axis. And the first envelope E81 has a plurality of bent portions. More specifically, the bent portion is a portion where the direction in which the envelope extends changes. In the present embodiment, the shape of the first envelope E81 is a wave-like shape in which adjacent bent portions are connected by a straight line. However, the shape of the first envelope E81 may be a wave-like shape in which adjacent bent portions are connected by a curve.

[0263] Similarly, the second envelope E82, the third envelope E83, and the fourth envelope E84 also each have a plurality of portions inclined with respect to the propagation axis. The second envelope E82, the third envelope E83, and the fourth envelope E84 each have a plurality of bent portions. The shapes of the second envelope E82, the third envelope E83, and the fourth envelope E84 are wave-like shapes in which adjacent bent portions are connected by a straight line. However, the shapes of the second envelope E82, the third envelope E83, and the fourth envelope E84 may be wave-like shapes in which adjacent bent portions are connected by a curve.

[0264] As described above, in the present embodiment, the first envelope E81, the second envelope E82, the third envelope E83, and the fourth envelope E84 have a plurality of bent portions. Note that at least any one of the first envelope E81, the second envelope E82, the third envelope E83, and the fourth envelope E84 may have at least one bent portion.

[0265] The end edges of the first busbar 83 on the side of the multiple first floating electrodes 81 extend parallel to the third envelope E83. Therefore, these end edges have multiple bends. The shape of these end edges is wavy, with adjacent bends connected by straight lines.

[0266] The ends of the second busbar 84 on the side of the second floating electrodes 82 extend parallel to the fourth envelope E84. Therefore, the ends have multiple bends. The shape of the ends is wavy, with adjacent bends connected by straight lines.

[0267] A mass-adding film is provided in the first edge region H1, the second edge region H2, the first floating electrode formation region U1, and the second floating electrode formation region U2, respectively, similar to the second embodiment. As a result, low-sonic regions are formed in the first edge region H1, the second edge region H2, the first floating electrode formation region U1, and the second floating electrode formation region U2, respectively. This allows for the suppression of transverse modes in this embodiment as well, and effectively reduces the leakage of elastic wave energy.

[0268] Incidentally, the laminated structure of the piezoelectric substrate is not limited to the configuration shown in Figure 2. The ninth embodiment shows an example in which the elastic wave device has a piezoelectric substrate different from that of the first embodiment.

[0269] Figure 33 is a schematic front cross-sectional view of an elastic wave apparatus according to the ninth embodiment.

[0270] This embodiment differs from the first embodiment in the laminated structure of the piezoelectric substrate 92. 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.

[0271] The piezoelectric substrate 92 comprises a support substrate 4, an intermediate layer 95, and a piezoelectric layer 6. The intermediate layer 95 is provided on the support substrate 4. The piezoelectric layer 6 is provided on the intermediate layer 95. In this embodiment, the intermediate layer 95 has a frame-like shape, that is, the intermediate layer 95 has through holes. The support substrate 4 blocks one of the through holes in the intermediate layer 95. The piezoelectric layer 6 blocks the other of the through holes in the intermediate layer 95. As a result, a hollow portion 92c is formed in the piezoelectric substrate 92. A part of the piezoelectric layer 6 and a part of the support substrate 4 face each other with the hollow portion 92c in between.

[0272] 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 transverse mode can be suppressed, and leakage of the elastic wave energy can be suppressed.

[0273] In the following, a first and second modification of the ninth embodiment are shown, in which only the laminated structure of the piezoelectric substrate differs from that of the ninth embodiment. In the first and second modifications, as in the ninth embodiment, transverse modes can be suppressed and the leakage of elastic wave energy can be suppressed.

[0274] In the first modified example shown in Figure 34, the piezoelectric substrate 92A includes a support substrate 4, an acoustic reflective film 97, an intermediate layer 95A, and a piezoelectric layer 6. The acoustic reflective film 97 is provided on the support substrate 4. The intermediate layer 95A is provided on the acoustic reflective film 97. The piezoelectric layer 6 is provided on the intermediate layer 95A. The intermediate layer 95A is a low-sound velocity film.

[0275] The acoustic reflective film 97 is a laminate of multiple acoustic impedance layers. Specifically, the acoustic reflective film 97 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 97 are high acoustic impedance layer 97a, high acoustic impedance layer 97c, and high acoustic impedance layer 97e. 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 97 are low acoustic impedance layer 97b and low acoustic impedance layer 97d. The low acoustic impedance layers and high acoustic impedance layers are laminated alternately. The high acoustic impedance layer 97a is the layer located closest to the piezoelectric layer 6 in the acoustic reflective film 97.

[0276] The acoustic reflective film 97 has two low acoustic impedance layers and three high acoustic impedance layers. However, the acoustic reflective film 97 only needs to have at least one low acoustic impedance layer and at least one high acoustic impedance layer.

[0277] 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 95A may be the same as the material of the low acoustic impedance layer.

[0278] In the second modified example shown in Figure 35, the piezoelectric substrate 92B has a support substrate 94 and a piezoelectric layer 6. The piezoelectric layer 6 is provided directly on the support substrate 94. More specifically, the support substrate 94 has a recess. The piezoelectric layer 6 is provided on the support substrate 94 so as to fill the recess. As a result, a hollow portion is provided in the piezoelectric substrate 92B. In a plan view, the hollow portion overlaps with at least a part of the IDT electrode 9.

[0279] Figure 36 is a schematic front cross-sectional view of an elastic wave apparatus according to the tenth embodiment.

[0280] This embodiment differs from the first embodiment in that 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 electrodes 9 provided on the second main surface 6b are embedded in the second layer 5b of the intermediate layer 5. Apart from the above, the elastic wave apparatus 100 of this embodiment has the same configuration as the elastic wave apparatus 10 of the first embodiment.

[0281] The IDT electrodes 9 provided on the first main surface 6a and the second main surface 6b of the piezoelectric layer 6 face each other across the piezoelectric layer 6. In the elastic wave apparatus 100, the IDT electrodes 9 and the mass-adding film are configured on the first main surface 6a in the same manner as in the first embodiment. This makes it possible to suppress transverse modes and reduce the leakage of elastic wave energy.

[0282] Furthermore, 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 differ from each other.

[0283] In the following, we show the first to third modifications of the 10th embodiment, in which at least one of the configuration of the electrodes provided on the second main surface of the piezoelectric layer and the laminated structure of the piezoelectric substrate differs from that of the 10th embodiment. In the first to third modifications, as in the 10th embodiment, transverse modes can be suppressed and leakage of elastic wave energy can be suppressed.

[0284] In the first modified example shown in Figure 37, the piezoelectric substrate 92 is configured in the same way as in the ninth embodiment. Specifically, the piezoelectric substrate 92 has a support substrate 4, an intermediate layer 95, 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 92c. In this modified example, a dielectric film 19 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 19 may be the same as the material of the intermediate layer 95, or it may be a different material from the material of the intermediate layer 95. However, the dielectric film 19 is not necessarily required.

[0285] In the second modified example shown in Figure 38, a plate-shaped electrode 108 is provided on the second main surface 6b of the piezoelectric layer 6. The IDT electrode 9 and the electrode 108 face each other with the piezoelectric layer 6 in between. The electrode 108 is embedded in the second layer 5b.

[0286] In the third modified example shown in Figure 39, the piezoelectric substrate 92 is configured in the same way as in the first modified example, and an electrode 108 similar to that in the second modified example is provided on the second main surface 6b of the piezoelectric layer 6. The electrode 108 is located within the hollow portion 92c. A dielectric film 19 is provided on the second main surface 6b so as to cover the electrode 108. However, the dielectric film 19 is not necessarily required.

[0287] The ninth and tenth embodiments and their respective modifications show examples where the IDT electrode 9 and the mass addition film have the same configuration as in the first embodiment. The piezoelectric substrate of the ninth embodiment and its respective modifications can also be used when the configuration of the IDT electrode and mass addition film is a configuration of the present invention other than that of the first embodiment. Alternatively, the piezoelectric substrate of the ninth embodiment and its respective modifications can be used even when the electrode fingers or floating electrodes of the IDT electrode have wide portions. However, in the present invention, the piezoelectric substrate may consist only of a piezoelectric layer. The configuration of the second main surface in the piezoelectric layer, similar to that of the tenth embodiment and its respective modifications, can also be used when the configuration of the IDT electrode and mass addition film is a configuration of the present invention other than that of the first embodiment, or when the electrode fingers or floating electrodes have wide portions.

[0288] The elastic wave apparatus according to the present invention can be used, for example, in a filter apparatus. This example is shown below.

[0289] Figure 40 is a circuit diagram of a filter device according to the eleventh embodiment.

[0290] The filter device 110 of this embodiment is a ladder-type filter. The filter device 110 has a first signal terminal 112 and a second signal terminal 113, and a plurality of series arm resonators and a plurality of parallel arm resonators. In the filter device 110, all series arm resonators and all parallel arm resonators are elastic wave resonators. Furthermore, all series arm resonators and all parallel arm resonators are elastic wave devices according to the present invention. However, it is sufficient that at least one of the plurality of elastic wave resonators in the filter device 110 is an elastic wave device according to the present invention.

[0291] The first signal terminal 112 is an antenna terminal. The antenna terminal is connected to an antenna. However, the first signal terminal 112 does not necessarily have to be an antenna terminal. The first signal terminal 112 and the second signal terminal 113 may be configured as, for example, electrode pads or as wiring.

[0292] The multiple series-arm resonators in this embodiment are specifically series-arm resonators S1, S2, and S3. The multiple series-arm resonators are connected in series with each other between the first signal terminal 112 and the second signal terminal 113. The multiple parallel-arm resonators are specifically parallel-arm resonators P1 and P2. Parallel-arm resonator P1 is connected between the connection point between series-arm resonators S1 and S2 and the ground potential. Parallel-arm resonator P2 is connected between the connection point between series-arm resonators S2 and S3 and the ground potential. Note that the circuit configuration of the filter device 110 is not limited to the above. The filter device 110 may include, for example, a longitudinally coupled resonator type elastic wave filter.

[0293] The elastic wave resonator in the filter device 110 is an elastic wave device according to the present invention. Therefore, the transverse mode can be suppressed in the elastic wave resonator of the filter device 110, and leakage of elastic wave energy can be suppressed.

[0294] The following shows an example of the procedure for reading the shape of the electrode fingers of an IDT electrode and the reflector electrode fingers of a reflector.

[0295] 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.

[0296] 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. Next, the extracted contour of the electrode finger's end is interpolated using a polynomial-approximated curve within an appropriate region size.

[0297] Next, the centroid is determined from the curves at both ends of the electrode finger. Here, the centroid is assumed to be a linear centroid. Specifically, first, any two adjacent points on the curves at both ends are connected by straight lines. Similarly, multiple pairs of points are connected by multiple straight lines. The line connecting the midpoints of these lines is taken as the centroid.

[0298] The curve obtained by polynomial approximation of the above linear centroid in a local region is defined as the curve representing the centroid. From the equation of this curve, the normal direction at each coordinate point on the centroid is calculated. Next, 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.

[0299] As mentioned above, curvature represents the degree to which a curve or surface is bent. Alternatively, the radius of a locally approximated circular arc at any point on the curve can be calculated, and the reciprocal of this radius can be expressed as the curvature. That is, if the calculated radius is r, the curvature is 1 / r. [Explanation of Symbols]

[0300] 2… Piezoelectric substrate 3…Support member 4…Support board 5…Middle class 5a, 5b... 1st and 2nd layers 6…Piezoelectric layer 6a, 6b…First and second principal surfaces 7A,7B…Reflector 8A~8C…1st to 3rd mass-addition membranes 9,9B,9C…IDT electrode 10... Elastic wave device 11...First floating electrode 13, 13B... First bus bar 13a...Inner busbar section 13b...Outer busbar section 13c...connection part 13d…Opening 14,14C...Second bus bar 14a...Inner busbar section 14b...Outer busbar section 14c...connection part 14d…Opening 15, 16… First and second electrode fingers 17,18…First and second offset electrodes 19… Dielectric film 20... Elastic wave device 22...Second floating electrode 28D...Fourth mass-addition membrane 29…IDT electrode 30... Elastic wave device 39,39A…Protective film 39a, 39b... First and second protective layers 40... Elastic wave device 51...First floating electrode 51a...Second wide section 52...Second floating electrode 52b...Fourth wide section 55...First electrode finger 55b...Third wide section 56...Second electrode finger 56a...First wide section 59…IDT electrode 65, 65A... First electrode finger 66, 66A... Second electrode finger 67A,67B…Reflector 69,69A…IDT electrode 70... Elastic wave device 75, 76… First and second electrode fingers 75c, 76c… First and second intersections 75d, 76d... First and second intersections 79…IDT electrode 80... Elastic wave device 81, 82… First and second floating electrodes 83, 84… 1st and 2nd bus bars 85, 86... First and second electrode fingers 87A,87B…Reflector 89…IDT electrode 92, 92A, 92B… Piezoelectric substrates 92c…Hollow part 94...Support board 95,95A…Middle layer 97…Acoustic reflective film 97a... High acoustic impedance layer 97b... Low acoustic impedance layer 97c... High acoustic impedance layer 97d... Low acoustic impedance layer 97e... High acoustic impedance layer 100... Elastic wave device 108...Electrode 110…Filter device 112, 113… First and second signal terminals 203... First bus bar 203d…opening 207...First offset electrode 209A,209B…IDT electrode A...Cross area F…Central area G...Gap area G1-G4...Gap regions 1-4 H1, H2… First and second edge regions J…Parallel area K…non-parallel region P1, P2… Parallel arm resonators S1~S3...Series arm resonator T…straight line area T1, T2… First and second linear regions U1, U2…First and second floating electrode formation regions W…Curve area 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, a plurality of electrode fingers, and a plurality of first floating electrodes that are not connected to the pair of busbars and the plurality of electrode fingers, Equipped with, 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. In the direction of elastic wave propagation, the region where adjacent first electrode fingers and second electrode fingers overlap is the intersection region, and when the direction perpendicular to the direction of elastic wave propagation is defined as the propagation orthogonal direction, the intersection region has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region facing each other with the central region in between, wherein the first edge region is located on the first busbar side, and the second edge region is located on the second busbar side. The plurality of first floating electrodes are located between the first edge region and the first busbar, and the region where the plurality of first floating electrodes are provided is the first floating electrode forming region. The first mass-adding film provided in the first edge region, The second mass-adding film provided in the first floating electrode formation region, An elastic wave device, further equipped with these features.

2. A piezoelectric substrate including a piezoelectric layer, An IDT electrode is provided on the piezoelectric layer and has a pair of busbars, a plurality of electrode fingers, and a plurality of first floating electrodes that are not connected to the pair of busbars and the plurality of electrode fingers, Equipped with, 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. In the direction of elastic wave propagation, the region where adjacent first electrode fingers and second electrode fingers overlap is the intersection region, and when the direction perpendicular to the direction of elastic wave propagation is defined as the propagation orthogonal direction, the intersection region has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region facing each other with the central region in between, wherein the first edge region is located on the first busbar side, and the second edge region is located on the second busbar side. The plurality of first floating electrodes are located between the first edge region and the first busbar, and the region where the plurality of first floating electrodes are provided is the first floating electrode forming region. In the first edge region, at least one of the plurality of first electrode fingers and the plurality of second electrode fingers has a first wide portion that is wider than the width in the central region. An elastic wave apparatus having at least one of the following configurations in the first floating electrode forming region: the plurality of first electrode fingers having a second wide portion that is wider than the width in the central region, and the plurality of first floating electrodes having a second wide portion that is wider than the other portions.

3. A piezoelectric substrate including a piezoelectric layer, An IDT electrode is provided on the piezoelectric layer and has a pair of busbars, a plurality of electrode fingers, and a plurality of first floating electrodes that are not connected to the pair of busbars and the plurality of electrode fingers, Equipped with, 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. In the direction of elastic wave propagation, the region where adjacent first electrode fingers and second electrode fingers overlap is the intersection region, and when the direction perpendicular to the direction of elastic wave propagation is defined as the propagation orthogonal direction, the intersection region has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region facing each other with the central region in between, wherein the first edge region is located on the first busbar side, and the second edge region is located on the second busbar side. The plurality of first floating electrodes are located between the first edge region and the first busbar, and the region where the plurality of first floating electrodes are provided is the first floating electrode forming region. The first mass-adding film is provided in the first edge region, An elastic wave apparatus having at least one of the following configurations in the first floating electrode forming region: the plurality of first electrode fingers having a second wide portion that is wider than the width in the central region, and the plurality of first floating electrodes having a second wide portion that is wider than the other portions.

4. A piezoelectric substrate including a piezoelectric layer, An IDT electrode is provided on the piezoelectric layer and has a pair of busbars, a plurality of electrode fingers, and a plurality of first floating electrodes that are not connected to the pair of busbars and the plurality of electrode fingers, Equipped with, 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. In the direction of elastic wave propagation, the region where adjacent first electrode fingers and second electrode fingers overlap is the intersection region, and when the direction perpendicular to the direction of elastic wave propagation is defined as the propagation orthogonal direction, the intersection region has a central region located on the central side in the propagation orthogonal direction, and a first edge region and a second edge region facing each other with the central region in between, wherein the first edge region is located on the first busbar side, and the second edge region is located on the second busbar side. The plurality of first floating electrodes are located between the first edge region and the first busbar, and the region where the plurality of first floating electrodes are provided is the first floating electrode forming region. In the first edge region, at least one of the plurality of first electrode fingers and the plurality of second electrode fingers has a first wide portion that is wider than the width in the central region. An elastic wave apparatus further comprising a second mass-adding film provided in the first floating electrode formation region.

5. The acoustic wave apparatus according to any one of claims 1 to 4, further comprising a third mass-adding film provided in the second edge region.

6. The elastic wave apparatus according to any one of claims 1 to 5, wherein in the second edge region, at least one of the plurality of first electrode fingers and the plurality of second electrode fingers has a third wide portion that is wider than the width in the central region.

7. The IDT electrode further comprises a plurality of second floating electrodes that are not connected to the first busbar, the second busbar, the plurality of first electrode fingers, and the plurality of second electrode fingers, and are located between the second edge region and the second busbar. The region where the plurality of second floating electrodes are provided is the second floating electrode forming region. The elastic wave apparatus according to any one of claims 1 to 6, further comprising a fourth mass-adding film provided in the second floating electrode forming region.

8. The IDT electrode further comprises a plurality of second floating electrodes that are not connected to the first busbar, the second busbar, the plurality of first electrode fingers, and the plurality of second electrode fingers, and are located between the second edge region and the second busbar. The region where the plurality of second floating electrodes are provided is the second floating electrode forming region. The elastic wave apparatus according to any one of claims 1 to 7, wherein in the second floating electrode forming region, the plurality of second electrode fingers have a fourth wide portion that is wider than the width in the central region, and the plurality of second floating electrodes have a fourth wide portion that is wider than the other portions.

9. The elastic wave apparatus according to any one of claims 1 to 8, wherein when a virtual line formed by connecting the tips of the plurality of second electrode fingers is defined as the first envelope, the direction in which the first envelope extends intersects with the direction in which the plurality of first electrode fingers and the plurality of second electrode fingers extend, and are not orthogonal to each other.

10. The elastic wave apparatus according to claim 9, wherein the direction in which the first envelope extends and the direction in which the plurality of first floating electrodes extend intersect and are not orthogonal to each other.

11. The elastic wave apparatus according to any one of claims 1 to 10, wherein the plan view shapes of the plurality of first electrode fingers and the plurality of second electrode fingers include a curved shape.

12. The elastic wave apparatus according to claim 11, wherein the plan view shapes of the plurality of first electrode fingers and the plurality of second electrode fingers include the shape of a circular arc or an elliptical arc.

13. When the imaginary line formed by connecting the tips of the plurality of second electrode fingers is called the first envelope, and the imaginary line formed by connecting the tips of the plurality of first electrode fingers is called the second envelope, the portion of the first electrode finger that includes the portion located on the first envelope and is adjacent to any tip of the second electrode finger is the adjacent portion of the first electrode finger, and the portion of the second electrode finger that includes the portion located on the second envelope and is adjacent to any tip of the first electrode finger is the adjacent portion of the second electrode finger, The elastic wave apparatus according to claim 11, wherein in the intersection region, the curvature of each of the first electrode fingers and the second electrode fingers is not constant, and the curvature differs between the tip portions located on the first envelope side, between adjacent portions, or between the tip portion and the adjacent portion of at least one pair of electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers.

14. When the regions in which the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view are curved are defined as curved regions, the intersection region includes at least one of the curved regions. When the imaginary line formed by connecting the tips of the plurality of second electrode fingers is called the first envelope, and the imaginary line formed by connecting the tips of the plurality of first electrode fingers is called the second envelope, when the imaginary line extending parallel to the first envelope or the second envelope and passing through the central region in the intersection region is called the intersection line, the intersection line is the edge of one of the curved regions, In each of the first electrode fingers, the portion that intersects with the cross line is the first intersection, and in each of the second electrode fingers, the portion that intersects with the cross line is the second intersection. The elastic wave apparatus according to claim 11, wherein in the curved region, the curvature of each of the first electrode fingers and the second electrode fingers is not constant, and the curvature of at least one pair of electrode fingers among the plurality of first electrode fingers and the plurality of second electrode fingers differs from that of the first intersection and the second intersection.

15. The elastic wave apparatus according to any one of claims 11 to 13, wherein the shape of the plurality of first floating electrodes in a plan view is curved.

16. The elastic wave apparatus according to any one of claims 11 to 15, wherein the resonant frequency or anti-resonant frequency of the main mode substantially coincides in the crossover region.

17. The piezoelectric layer has a propagation axis, In the aforementioned intersection region, the excitation direction of the elastic wave in any portion of any electrode finger among the plurality of first electrode fingers and the plurality of second electrode fingers is one of the first to third directions, wherein 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 or second electrode finger, and the third direction is the direction of the electric field vector generated between the electrode finger and the adjacent first or second electrode finger. The elastic wave apparatus according to claim 16, wherein, when the excitation angle is defined as the angle between the excitation direction and the direction in which the propagation axis extends, at least one of the duty cycle, electrode finger pitch, and thickness of the plurality of first electrode fingers and the plurality of second electrode fingers is constant in the portion of the IDT electrode where the excitation angle is the same.

18. In the portion of the IDT electrode where the excitation angle is the same, the duty cycle is constant. The elastic wave apparatus according to claim 17, wherein, in at least a portion of the crossover region, the duty cycle of the IDT electrode in the portion where the excitation angle is the same increases or decreases as the absolute value of the excitation angle increases, such that the resonant frequency or anti-resonant frequency of the main mode substantially coincides.

19. In the portion of the IDT electrode where the excitation angle is the same, the electrode finger pitch is constant. The elastic wave apparatus according to claim 17 or 18, wherein, in at least a portion of the crossover region, the electrode finger pitch of the IDT electrode in the portion where the excitation angle is the same is wider or narrower as the absolute value of the excitation angle increases, such that the resonant frequency or anti-resonant frequency of the main mode substantially coincides.

20. In the portion of the IDT electrode where the excitation angle is the same, the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers is constant. The elastic wave apparatus according to any one of claims 17 to 19, wherein, in at least a portion of the crossover region, the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers in the portions where the excitation angles are the same increases or decreases as the absolute value of the excitation angle increases, such that the resonant frequency or anti-resonant frequency of the main mode substantially coincides.

21. 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 20, 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.

22. The elastic wave apparatus according to any one of claims 1 to 21, wherein the wavelength is defined by the electrode finger pitch, and the imaginary line formed by connecting the tips of the plurality of floating electrodes on the first busbar side is defined as the third envelope, and the dimension of the region between the third envelope and the first busbar along the normal direction of the third envelope is 1λ or more.

23. The piezoelectric substrate has a support substrate, The elastic wave apparatus according to any one of claims 1 to 22, wherein the piezoelectric layer is provided on the support substrate.

24. The elastic wave apparatus according to claim 23, wherein the piezoelectric substrate has an intermediate layer provided between the support substrate and the piezoelectric layer.

25. The elastic wave apparatus according to claim 23 or 24, 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.

26. The elastic wave apparatus according to any one of claims 1 to 22, wherein the piezoelectric substrate consists only of the piezoelectric layer.

27. Equipped with multiple elastic wave resonators, A filter device wherein at least one of the elastic wave resonators is an elastic wave device according to any one of claims 1 to 26.

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