Elastic wave device and filter device

Abstract

Provided is an elastic wave device with which it is possible to sufficiently suppress unwanted waves and transverse modes outside a passband, and with which it is possible to suppress deterioration in resonance characteristics. This elastic wave device is provided with: a piezoelectric substrate that includes a piezoelectric layer; and an IDT electrode (8) that is provided on the piezoelectric layer. The IDT electrode (8) has a first bus bar (14) and a second bus bar (15) facing each other, a plurality of first electrode fingers (16) each having one end connected to the first bus bar (14), and a plurality of second electrode fingers (17) each having one end connected to the second bus bar (15). The plurality of first electrode fingers (16) and the plurality of second electrode fingers (17) are interleaved and inserted with each other. An imaginary line formed by connecting the tips of the plurality of second electrode fingers (17) is defined as a first envelope line (E1), an imaginary line formed by connecting the tips of the plurality of first electrode fingers (16) is defined as a second envelope line (E2), and a region between the first envelope line (E1) and the second envelope line (E2) in the IDT electrode (8) is an intersection region (D). The shape of each of the plurality of first electrode fingers (16) and the plurality of second electrode fingers (17) in a plan view includes at least two curved portions in which the directions in which the first electrode fingers (16) and the second electrode fingers (17) bend are different in an intersection region (D). In the intersection region (D), the value of at least one of the duty ratio, the electrode finger pitch, and the thickness of the plurality of first electrode fingers (16) and the plurality of second electrode fingers (17) changes in one of a direction in which the value increases and a direction in which the value decreases as the value is closer to the first envelope (E1) or the second envelope (E2).

Description

Technical Field

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

[0002] In the past, elastic wave devices have been widely used in filters of portable phones, etc. An example of an elastic wave device is disclosed in the following patent document 1. In this elastic wave device, an IDT (Interdigital Transducer) electrode is provided on a piezoelectric substrate. The shape of the multiple electrode fingers of the IDT electrode includes a curved shape. More specifically, each electrode finger extends along a curved line from the center of the area where the IDT electrodes intersect to the common electrode.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2011 / 108229 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the IDT electrode of the elastic wave device described in Patent Document 1, the electrode finger pitch in the center portion in the direction in which the plurality of electrode fingers extend is narrower than the electrode finger pitch in the end portion in the direction. Therefore, the effect of suppressing the response of the unnecessary wave to a certain extent can be obtained. However, since the resonance frequency is different for each portion of the IDT electrode, the resonance characteristics may be degraded. In addition, the unnecessary wave cannot be fully suppressed.

[0008] An object of the present invention is to provide an elastic wave device and a filter device that can sufficiently suppress unnecessary waves and transverse modes outside a passband and suppress degradation of resonance characteristics.

[0009] Technical solutions to solve problems

[0010] In a broad aspect of the elastic wave device involved in the present invention, it comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode arranged on the piezoelectric layer, the IDT electrode having a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers being interlaced with each other, an imaginary line formed by connecting the top ends of the plurality of second electrode fingers being set as a first envelope, and an imaginary line formed by connecting the top ends of the plurality of first electrode fingers being set as a second envelope. 2 envelopes, the area between the first envelope and the second envelope in the IDT electrode is an intersection area, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view respectively include at least two curved portions in the intersection area in which the first electrode fingers and the second electrode fingers are bent in different directions, and in the intersection area, the closer to the first envelope or the second envelope, the more the value of at least any one of the duty cycle, the electrode finger pitch and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

[0011] In another broad aspect of the elastic wave device according to the present invention, the device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode disposed on the piezoelectric layer, the IDT electrode comprising a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers being interlaced with each other, an imaginary line formed by connecting the top ends of the plurality of second electrode fingers being a first envelope, and an imaginary line formed by connecting the top ends of the plurality of first electrode fingers being a second envelope, a region between the first envelope and the second envelope in the IDT electrode being an intersection region, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view each including the shapes of at least two circular arcs or elliptical arcs and having at least one inflection point, and the intersection region including the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view each including the shapes of at least two circular arcs or elliptical arcs, and having at least one inflection point, At least two curved areas in the shape of a single circular arc or an elliptical arc, the intersection area having a first edge area including the first envelope, a second edge area including the second envelope, and a central area sandwiched by the first edge area and the second edge area, at least one of the first edge area and the second edge area constituting a low sound velocity area having a sound velocity lower than that in the central area, and when the center of the circle of the circular arc or the midpoint of the two foci of the ellipse including the elliptical arc in the shape of each of the curved areas including the first electrode finger and the second electrode finger is set as a fixed point, and a portion of each of the curved areas located in the central area and on an arbitrary straight line passing through the fixed point is set as an excitation portion, the closer the excitation portion is to the first envelope or the second envelope, the more the value of at least any one of the duty cycle, the electrode finger pitch, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

[0012] A filter device according to the present invention includes a plurality of elastic wave resonators, and at least one of the elastic wave resonators is an elastic wave device configured according to the present invention.

[0013] Effects of the Invention

[0014] According to the elastic wave device and the filter device according to the present invention, unnecessary waves and transverse modes outside the passband can be sufficiently suppressed, and degradation of resonance characteristics can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention.

[0016] Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0017] Figure 3 It is a schematic plan view for explaining the structure of the IDT electrode in the first embodiment of the present invention.

[0018] Figure 4 It is a schematic top view of an IDT electrode in a comparative example.

[0019] Figure 5 It is a graph showing the impedance frequency characteristics in the first embodiment of the present invention and a comparative example.

[0020] Figure 6 It is a graph showing the return loss in the first embodiment of the present invention and the comparative example.

[0021] Figure 7 It is a diagram showing the phase characteristics in the first embodiment of the present invention and a comparative example.

[0022] Figure 8 It is a diagram showing the inverse velocity surface of the elastic wave propagating through the first piezoelectric substrate and the second piezoelectric substrate.

[0023] Fig. 9 It is a diagram showing the inverse velocity surfaces of the longitudinal wave, the fast transverse wave, and the slow transverse wave in the first piezoelectric substrate.

[0024] Fig.10 is an absolute value of the excitation angle |θ of the IDT electrode in the first embodiment, the first modification, and the second modification of the present invention. C1_prop |A graph showing the relationship between Ω and duty cycle.

[0025] Fig.11 It is a schematic top view of an IDT electrode in a reference example.

[0026] Fig.12 It is a graph showing the return loss in the first embodiment of the present invention and the reference example.

[0027] Fig.13 It is a diagram showing the impedance frequency characteristics in the first embodiment of the present invention and a reference example.

[0028] Fig.14 It is a diagram showing phase characteristics in the first embodiment and a reference example of the present invention.

[0029] Fig.15 It is a schematic front cross-sectional view of an elastic wave device according to a third modified example of the first embodiment of the present invention.

[0030] Fig.16It is a schematic front cross-sectional view of an elastic wave device according to a fourth modified example of the first embodiment of the present invention.

[0031] Fig.17 It is a schematic plan view of an elastic wave device according to a second embodiment of the present invention.

[0032] Fig.18 It is a schematic plan view for explaining the structure of an IDT electrode in the second embodiment of the present invention.

[0033] Fig.19 is an absolute value of the excitation angle |θ of the IDT electrode in the second embodiment of the present invention. C1_prop |A graph showing the relationship between Δpitch and the rate of change of the electrode finger pitch.

[0034] Fig. 20 It is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the third embodiment of the present invention.

[0035] Fig.21 This is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the first modification of the third embodiment of the present invention.

[0036] Fig. 22 This is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the second modified example of the third embodiment of the present invention.

[0037] Fig.23 It is a schematic plan view of an elastic wave device according to a fourth embodiment of the present invention.

[0038] Fig.24 It is a schematic plan view for explaining the structure of an IDT electrode in a fifth embodiment of the present invention.

[0039] Fig.25 It is a schematic plan view of an elastic wave device according to a first modified example of the fifth embodiment of the present invention.

[0040] Fig.26 This is a schematic plan view showing, in enlarged form, the first edge region and the second edge region of the IDT electrode in the first modification of the fifth embodiment of the present invention.

[0041] Fig. 27 It is a schematic plan view of an elastic wave device according to a second modified example of the fifth embodiment of the present invention.

[0042] Fig.28This is a schematic plan view showing, in an enlarged manner, the vicinity of the first edge region and the vicinity of the second edge region of the IDT electrode in the third modification of the fifth embodiment of the present invention.

[0043] Fig.29 It is a schematic plan view of an elastic wave device according to a fourth modified example of the fifth embodiment of the present invention.

[0044] Fig.30 It is a schematic plan view of an elastic wave device according to a sixth embodiment of the present invention.

[0045] Fig.31 It is a schematic plan view of an elastic wave device according to a seventh embodiment of the present invention.

[0046] Fig.32 It is a schematic plan view of an elastic wave device according to an eighth embodiment of the present invention.

[0047] Fig.33 is an absolute value of the excitation angle of the IDT electrode in the ninth embodiment of the present invention |θ C1_prop |A diagram showing the relationship between the thickness of the electrode fingers.

[0048] Fig.34 It is a schematic front cross-sectional view of an elastic wave device according to a tenth embodiment of the present invention.

[0049] Fig.35 θ represents the absolute value of the excitation angle in the excitation portion of the first curve region covered by the dielectric film in the tenth embodiment of the present invention. C1_prop |A graph showing the relationship between and the thickness of the dielectric film.

[0050] Fig.36 is an absolute value of the excitation angle |θ in the excitation portion of the first curve region covered by the dielectric film in the modification of the tenth embodiment of the present invention. C1_prop |A graph showing the relationship between and the thickness of the dielectric film.

[0051] Fig.37 This is a circuit diagram of a filter device according to an eleventh embodiment of the present invention.

[0052] Fig.38 This is a schematic plan view showing an enlarged portion of an IDT electrode in a fifth modification of the first embodiment of the present invention.

[0053] Fig.39 It is a schematic front cross-sectional view of an elastic wave device according to a twelfth embodiment of the present invention.

[0054] Fig.40It is a schematic front cross-sectional view of an elastic wave device according to a thirteenth embodiment of the present invention.

[0055] Fig.41 It is a schematic front cross-sectional view of an elastic wave device according to a first modified example of the thirteenth embodiment of the present invention.

[0056] Fig.42 It is a schematic front cross-sectional view of an elastic wave device according to a second modified example of the thirteenth embodiment of the present invention.

[0057] Fig.43 It is a schematic front cross-sectional view of an elastic wave device according to a third modified example of the thirteenth embodiment of the present invention. DETAILED DESCRIPTION

[0058] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention will be clarified.

[0059] In addition, it should be noted that each embodiment described in this specification is an example, and some structures can be replaced or combined among different embodiments.

[0060] Figure 1 It is a schematic plan view of the elastic wave device according to the first embodiment of the present invention. Figure 2 It is along Figure 1 Schematic cross-sectional view of line II in FIG.

[0061] like Figure 1 as well as Figure 2 As shown in FIG. 1 , the elastic wave device 1 includes a piezoelectric substrate 2. The piezoelectric substrate 2 is a substrate having piezoelectricity. Specifically, Figure 2 As shown, the piezoelectric substrate 2 has a supporting member 3 and a piezoelectric layer 6. More specifically, the supporting member 3 has a supporting 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 supporting substrate 4. The second layer 5b is provided on the first layer 5a. The piezoelectric layer 6 is provided on the second layer 5b. In addition, the layer structure of the piezoelectric substrate 2 is not limited to the above. For example, the intermediate layer 5 may also be a single-layer dielectric film. Alternatively, the piezoelectric substrate 2 may also be a substrate including only the piezoelectric layer 6.

[0062] like Figure 1As shown, an IDT electrode 8 is provided on the piezoelectric layer 6. The IDT electrode 8 has a plurality of first electrode fingers 16 and a plurality of second electrode fingers 17. In the present embodiment, the shape of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 when viewed from above is a shape that connects two arcs. More specifically, it is a shape that connects two arcs whose centers are at different positions and have the same radius. The centers of the two circles are opposite to each other with the IDT electrode 8 sandwiched between them. In this specification, the term "viewed from above" refers to a shape that is viewed from the direction equivalent to Figure 2 Observe from the top of the middle. Figure 2 For example, of the support substrate 4 side and the piezoelectric layer 6 side, the piezoelectric layer 6 side is the upper side. Hereinafter, the first electrode fingers 16 and the second electrode fingers 17 may be simply described as electrode fingers.

[0063] The shapes of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 when viewed from above each have inflection points. In this specification, an inflection point is a point where mutually different curves are connected to each other, or a point where a curve and a straight line are connected. At the inflection point, when mutually different curves are connected to each other, the orientation of the curved shape differs with the inflection point as a boundary. Here, the orientation of the curved shape of the electrode finger can be defined, for example, by the positional relationship between the electrode finger and a fixed point described in detail later. Specifically, the fixed point determined in each portion of the curved shape in the intersection area excluding the edge area described later can be present in the electrode finger, Figure 1 The direction of the curved shape is defined by which side of the left or right side. In this case, the shape of the electrode finger has at least two curved portions with different bending directions of the electrode finger. In the following embodiments, the two curved shapes are inverted with the inflection point as a boundary.

[0064] In addition, the shapes of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 in a top view are not limited to the above, and can be any shape including two or more different curved portions, especially circular arcs or elliptical arcs, and can be any shape including at least one inflection point. Specifically, the different curved portions can be circular arcs, elliptical arcs, or a combination of circular arcs and elliptical arcs. The following describes the details of the structure of the IDT electrode 8.

[0065] like Figure 1As shown, the IDT electrode 8 has a first bus bar 14 and a second bus bar 15, and a plurality of first offset electrodes 18 and a plurality of second offset electrodes 19 in addition to a plurality of first electrode fingers 16 and a plurality of second electrode fingers 17. The first bus bar 14 and the second bus bar 15 are opposed to each other. One end of the plurality of first electrode fingers 16 is connected to the first bus bar 14, respectively. One end of the plurality of second electrode fingers 17 is connected to the second bus bar 15, respectively. The plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 are interlaced with each other.

[0066] One end of each of the plurality of first offset electrodes 18 is connected to the first bus bar 14. The first electrode fingers 16 and the first offset electrodes 18 are arranged alternately. One end of each of the plurality of second offset electrodes 19 is connected to the second bus bar 15. The second electrode fingers 17 and the second offset electrodes 19 are arranged alternately.

[0067] The plurality of first electrode fingers 16 and the plurality of second electrode fingers 17, and the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 include base ends and top ends, respectively. The base ends of the first electrode fingers 16 and the first offset electrodes 18 are portions connected to the first bus bar 14. The base ends of the second electrode fingers 17 and the second offset electrodes 19 are portions connected to the second bus bar 15. The top ends of the first electrode fingers 16 and the top ends of the second offset electrodes 19 face each other with a gap g2 therebetween. On the other hand, the top ends of the second electrode fingers 17 and the top ends of the first offset electrodes 18 face each other with a gap g1 therebetween.

[0068] Hereinafter, the first offset electrode 18 and the second offset electrode 19 may be simply referred to as offset electrodes. The first bus bar 14 and the second bus bar 15 may be simply referred to as bus bars. The pitch or duty ratio of the offset electrodes may be different from the electrode finger pitch or duty ratio of the IDT electrode 8 in the intersection region described later, for example.

[0069] Figure 3 FIG. 1 is a schematic top view for explaining the structure of the IDT electrode in the first embodiment. Figure 3 In the figure, hatching is performed to indicate each curve region described later.

[0070] An imaginary line formed by connecting the top ends of the plurality of second electrode fingers 17 is referred to as the first envelope E1, and an imaginary line formed by connecting the top ends of the plurality of first electrode fingers 16 is referred to as the second envelope E2. The region between the first envelope E1 and the second envelope E2 is the intersection region D. More specifically, the region surrounded by the electrode fingers at one end in the direction in which the plurality of electrode fingers are arranged, the electrode fingers at the other end, the first envelope E1, and the second envelope E2 is the intersection region D. Therefore, the first envelope E1 corresponds to the end edge portion of the intersection region D on the first bus bar 14 side. The second envelope E2 corresponds to the end edge portion of the intersection region D on the second bus bar 15 side. In the intersection region D, when viewed from the direction in which the first envelope E1 or the second envelope E2 extends, adjacent electrode fingers overlap with each other.

[0071] As described above, the shapes of the multiple electrode fingers when viewed from above are shapes in which two arcs are connected. When viewed from above, one of the arcs in the shapes of the multiple electrode fingers is one of the arcs in a plurality of concentric circles. Therefore, the centers of the circles including the arcs in the shapes of the multiple electrode fingers are consistent. In the present embodiment, the centers of these circles are set to fixed point C1. When viewed from above, another of the arcs in the shapes of the multiple electrode fingers is also one of the arcs in a plurality of concentric circles. The centers of these circles are set to fixed point C2. Thus, in the present embodiment, two fixed points C1 and C2 are defined. Fixed point C1 and fixed point C2 are opposite to each other with the IDT electrode 8 sandwiched therebetween. However, the shape of the IDT electrode 8 may also be a shape in which more than three fixed points are defined.

[0072] In addition, the shape of the plurality of electrode fingers in a plan view may include an elliptical arc. In this case, the fixed point is the midpoint of the two foci of the elliptical arc. In other words, the center of the two foci is the centroid of the two foci.

[0073] Here, the elliptic coefficient of the shape of the plurality of electrode fingers in a top view is set to α2 / α1. In the present embodiment, since the shape of each electrode finger includes two circular arcs, two elliptic coefficients α2 / α1 can be defined. Specifically, the elliptic coefficient of the circle or ellipse based on the fixed point C1 in the shape of the plurality of electrode fingers is set to α12 / α11, and the elliptic coefficient of the circle or ellipse based on the fixed point C2 is set to α22 / α21. Both the elliptic coefficients α12 / α11 and α22 / α21 in the present embodiment are 1. In addition, in the case where the shape of the arc in the shape including the plurality of electrode fingers is an ellipse, the elliptic coefficients α12 / α11 and α22 / α21 become other than 1. α1, i.e., α11 and α21 correspond to the dimensions of the ellipse along the direction of the axis passing through the intersection region D among the major axis and the minor axis. α2, i.e., α21 and α22 correspond to the dimensions of the ellipse along the direction of the axis not passing through the intersection region D among the major axis and the minor axis.

[0074] When r1 is set to an arbitrary constant, the ellipticity coefficient in the XY plane can be expressed as (x / α11) 2 + (y / α12) 2 =r1 2 Similarly, when r2 is set to an arbitrary constant, the formula for the ellipticity coefficient in the XY plane can be expressed as (x / α21) 2 + (y / α22) 2 =r2 2 .

[0075] The intersection region D includes a plurality of curve regions. Specifically, in the present embodiment, the plurality of curve regions are a first curve region W1 and a second curve region W2. The first curve region W1 includes a first envelope E1. The second curve region W2 includes a second envelope E2. In each curve region, the shapes of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 in a top view are respectively single arc shapes or elliptical arc shapes. The boundary lines between different curve regions are equivalent to lines connecting the inflection points of the electrode fingers. The boundary line between the first curve region W1 and the second curve region W2 is a straight line. Moreover, the extension line of the boundary line passes through the fixed point C1 and the fixed point C2. In addition, in the present invention, the intersection region D only needs to include at least two curve regions.

[0076] By applying an AC voltage to the IDT electrode 8, elastic waves are excited in the intersection region D. In addition, the first curved region W1 in the intersection region D has portions located on countless straight lines passing through the fixed point C1. Figure 3 , the straight line M1 is shown as an example of the countless straight lines passing through the fixed point C1 and the first curved region W1. For example, elastic waves are excited in the portion located on the straight line M1 in the first curved region W1. Elastic waves are also excited in the portions located on countless straight lines (not shown) passing through the fixed point C1 and the first curved region W1. That is, the elastic wave device 1 has an excitation portion located on the straight line M1 and an excitation portion located on countless other straight lines (not shown).

[0077] In addition, the direction of the excited elastic wave becomes a direction perpendicular to the direction in which the tangent of each part of the electrode finger extends, or a direction connecting the shortest distance between adjacent electrode fingers, or a direction parallel to the electric field vector generated between the electrode fingers. The direction in which the electrode finger extends here refers to the direction in which the tangent of the curve connecting the parts of the electrode finger extends. In addition, each part of the electrode finger can be represented by the center of gravity or a point in the middle of the two ends. Figure 4In the conventional elastic wave resonator shown, the excitation direction of the elastic wave is the same regardless of the definition. When the curve is an arc centered at the fixed point C, the direction of the excited elastic wave is represented by the direction perpendicular to the direction in which the tangent line of the curve connecting the electrode fingers extends.

[0078] The second curve region W2 in the intersection region D also has numerous excitation portions. Figure 3 , a straight line M2 is shown as an example of the countless straight lines passing through the fixed point C2 and the second curved area W2. The excitation portion in the second curved area W2 is located on the straight line passing through the fixed point C2.

[0079] As described above, the extension line of the boundary line between the first curved region W1 and the second curved region W2 passes through the fixed point C1 and the fixed point C2. In the elastic wave device 1, a straight line including the boundary line and the extension line of the boundary line is set as a reference line N. Furthermore, an angle formed by a straight line passing through the fixed point C1 and the excitation portion in the first curved region W1 and the reference line N is set as an angle θ. C1 .exist Figure 3 As an example, the angle θ of the excitation part located on the straight line M1 is shown. C1 On the other hand, the angle formed by the straight line passing through the fixed point C2 and the excitation part in the second curve region W2 and the reference line N is defined as angle θ. C2 .exist Figure 3 As an example, the angle θ of the excitation part located on the straight line M2 is shown. C2 In this specification, the angle θ C1 The positive direction is the counterclockwise direction when viewed from above. More specifically, the direction from the second bus bar 15 side toward the first bus bar 14 side is the positive direction. C2 The positive direction is set to the clockwise direction when looking down.

[0080] The angle formed by the excitation direction of the elastic wave and the reference line N at the intersection of the straight line passing through the fixed point C1 and the excitation portion of the curve region W1 and the first electrode finger 16 or the second electrode finger 17 is defined as the excitation angle θ. C1_prop On the other hand, the angle formed by the excitation direction of the elastic wave and the reference line N at the intersection of the straight line passing through the fixed point C2 and the excitation portion of the curve region W2 and the first electrode finger 16 or the second electrode finger 17 is defined as the excitation angle θ. C2_prop . Excitation angle θ C1_prop and the excitation angle θ C2_prop The positive and negative directions are set to be angles θ C1 and the angle θ C2 The positive and negative directions are in the same direction.

[0081] Here, the angle θ in the excitation portion of the first curve region W1 is C1 and the excitation angle θ C1_prop Roughly the same. Below, the angle θ is used C1 and the excitation angle θ C1_prop The discussion is made at any angle, but there is no difference in the degree of influence such as the subversive action / effect produced between the two angles. C2 and the excitation angle θ C2_prop In addition, when the ellipticity coefficient α2 / α1 is 1, that is, when it becomes a circle, the angle θ C1 and the excitation angle θ C1_prop become equal. Angle θ C2 and the excitation angle θ C2_prop become equal.

[0082] In each curve region, the angle formed by a straight line passing through the edge portion and a fixed point on the first bus bar 14 side and the reference line N, and the angle formed by a straight line passing through the edge portion and a fixed point on the second bus bar 15 side and the reference line N are respectively referred to as intersection angles. In addition, the intersection angle in the first curve region W1 is referred to as θ C1_AP , let the intersection angle in the second curve area W2 be θ C2_AP More specifically, in this embodiment, the intersection angle θ in the first curve region W1 is C1_AP is the angle formed by the straight line passing through the first envelope E1 and the fixed point C1 and the reference line N. In this case, 0≤θ C1 ≤θ C1_AP On the other hand, the intersection angle θ in the second curve region W2 C2_AP is the angle formed by the straight line passing through the second envelope E2 and the fixed point C2 and the reference line N. In this case, 0≤θ C2 ≤θ C2_AP In the elastic wave device 1 , the intersection angle θ of the first curved region W1 is C1_AP and the intersection angle θ of the second curve region W2 C2_AP However, the intersection angle θ of the first curve area W1 is C1_AP and the intersection angle θ of the second curve region W2 C2_AP They may also be different from each other.

[0083] A piezoelectric single crystal is used as a material of the piezoelectric layer 6 of the elastic wave device 1. In the piezoelectric layer 6, the propagation axis is the direction of X propagation. In the present embodiment, the straight line extending parallel to the propagation axis among the straight lines passing through the intersection region D and the fixed point C is the reference line N. However, the reference line N does not necessarily need to extend parallel to the propagation axis.

[0084] The propagation axis may be not only the X propagation direction but also a direction perpendicular to the 90° X propagation direction or the direction in which the electrode fingers of the IDT electrode 8 extend. The electrode finger extending direction here refers to the direction in which the tangent of each portion of the electrode finger extends.

[0085] In the excitation part through which the reference line N passes, the angle θ C1 and the angle θ C2 , and the excitation angle θ C1_prop and the excitation angle θ C2_prop is 0°. Between each excitation part, the excitation angle θ C1_prop Or the excitation angle θ C2_prop Different from each other, the propagation characteristics of the elastic waves are different from each other. In contrast, in the present embodiment, the duty ratios are made different between the multiple excitation parts so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are roughly the same. In addition, the absolute value of the excitation angle |θ C1_prop |or|θ C2_prop |The duty ratio is the same between the same excitation parts. Since the IDT electrode 8 is configured as described above, the resonance characteristics are unlikely to deteriorate. However, the duty ratio may be fixed.

[0086] In addition, in this specification, the term "one frequency and another frequency are roughly consistent" means that the absolute value of the difference between the two frequencies is less than 2% relative to the reference frequency. In addition, the so-called reference frequency is the frequency when the excitation angle in each curve area is 0°. In each curve area, it is preferred that the absolute value of the difference between the highest resonant frequency and the lowest resonant frequency of the main mode is less than 1% relative to the reference frequency. Alternatively, in each curve area, it is preferred that the absolute value of the difference between the highest anti-resonant frequency and the lowest anti-resonant frequency of the main mode is less than 1% relative to the reference frequency.

[0087] In IDT electrode 8 of elastic wave device 1 , the electrode finger pitch is fixed. Therefore, when the wavelength defined by the electrode finger pitch is λ, the wavelength λ in IDT electrode 8 does not depend on the excitation angle θ. C1_prop and the excitation angle θ C2_prop The electrode finger pitch is the distance between the centers of the adjacent first electrode fingers 16 and second electrode fingers 17. When the electrode finger pitch is denoted as p, λ=2p.

[0088] In the IDT electrode 8, the first envelope E1 and the first bus bar 14 extend in parallel. Similarly, the second envelope E2 and the second bus bar 15 extend in parallel. When the angle formed by the reference line N and the bus bar is set as the bus bar inclination angle, the bus bar inclination angles of the first bus bar 14 and the second bus bar 15 are the same. However, the bus bar inclination angles of the first bus bar 14 and the second bus bar 15 may be different from each other. In this specification, the positive direction of the bus bar inclination angle is set to the counterclockwise direction when viewed from above.

[0089] A pair of reflectors 9A and 9B are provided on the piezoelectric layer 6. The reflectors 9A and 9B face each other with the IDT electrode 8 sandwiched therebetween in the direction in which the plurality of electrode fingers of the IDT electrode 8 are arranged. The reflector 9A has a plurality of electrode fingers 9a. The reflector 9B has a plurality of electrode fingers 9b. The shapes of the plurality of electrode fingers 9a of the reflector 9A and the shapes of the plurality of electrode fingers 9b of the reflector 9B in a plan view are shapes connecting two arcs. Specifically, these arcs correspond to each of the arcs in a plurality of concentric circles. More specifically, the center of a circle including one of the shapes of the plurality of electrode fingers 9a and the plurality of electrode fingers 9b coincides with a fixed point C1. The center of a circle including another arc coincides with a fixed point C2. In addition, the shape of the electrode fingers of each reflector may be a shape of a curve or a straight line different from the shape of the electrode fingers of the IDT electrode 8 in the excitation portion. The structural parameters such as the electrode finger pitch or duty ratio of each reflector may also be different from the structural parameters of the electrode fingers of the IDT electrode 8 in the excitation portion. The electrode fingers of each reflector may be formed in a pattern different from the shape of the electrode fingers of the IDT electrode 8 in the excitation portion.

[0090] The present embodiment is characterized in that the intersection region D includes a plurality of curve regions, and in the intersection region D, the duty ratio changes in one of a direction of increasing and a direction of decreasing as the portion is closer to the first envelope E1 or the second envelope E2. C1_prop and the excitation angle θ C2_prop The duty cycle is the largest in the excitation section with an angle of 0°, and the closer the excitation section is to the first envelope E1 or the second envelope E2, the smaller the duty cycle. Accordingly, it is possible to suppress useless waves and transverse modes outside the passband. In addition, in this specification, the so-called outside the passband in the elastic wave device refers to the low frequency side compared to the resonant frequency and the high frequency side compared to the anti-resonant frequency. The following is a comparison of the present embodiment and the comparative example to show the details of the above effect.

[0091] In the comparative example, Figure 4As shown, each electrode finger of the IDT electrode 208, the reflector 209A, and the reflector 209B is linear. In the IDT electrode 208, the intersection region is rectangular. In the elastic wave devices of the first embodiment and the comparative example, the impedance frequency characteristics, the return loss, and the phase characteristics are compared. In addition, the design parameters of the elastic wave device 1 of the first embodiment are as follows. Here, the dimension of the offset electrode along the direction connecting the base end portion (the root portion) and the tip portion is set as the length of the offset electrode.

[0092] Support substrate 4: Material: Si, plane orientation: (111), ψ of the Euler angles (φ, θ, ψ): 73°

[0093] First layer 5a: material…SiN, thickness…0.15λ

[0094] Second layer 5b: material…SiO2, thickness…0.15λ

[0095] Piezoelectric layer 6: Material: LiTaO3 with rotation Y-cut 55° X-propagation, thickness: 0.2λ

[0096] IDT electrode 8: material…Al, thickness…0.05λ,

[0097] Number of pairs of electrode fingers of IDT electrode 8: 100 pairs

[0098] Ellipticity coefficient of electrode finger shape α12 / α11:1

[0099] Ellipticity coefficient of electrode finger shape α22 / α21: 1

[0100] Crossing angle θ C1_AP : 7.5°

[0101] Crossing angle θ C2_AP : 7.5°

[0102] Wavelength λ: 2μm

[0103] Duty cycle: At the excitation angle θ C1_prop and the excitation angle θ C1_prop 0.5 in the excitation section at 0°

[0104] The bus bar inclination angle of the first bus bar 14 and the second bus bar 15 is 7.5°

[0105] Length of the first offset electrode 18 and the second offset electrode 19: 3.5λ

[0106] Reflector 9A and reflector 9B: Number of pairs of electrode fingers: 20 pairs

[0107] On the other hand, when the direction in which the plurality of electrode fingers extend is defined as the electrode finger extension direction and the dimension of the intersection region along the electrode finger extension direction is defined as the intersection width, the intersection width in the IDT electrode 208 of the elastic wave device of the comparative example is 41.5λ. The number of pairs of electrode fingers of the IDT electrode 208 is 60, and the number of pairs of electrode fingers of the reflector 209A and the reflector 209B are 20, respectively. In the IDT electrode 208, the duty ratio is 0.5.

[0108] Figure 5 It is a graph showing the impedance frequency characteristics in the first embodiment and the comparative example. Figure 6 It is a graph showing the return loss in the first embodiment and the comparative example. Figure 7 It is a diagram showing the phase characteristics in the first embodiment and the comparative example.

[0109] like Figure 5 as well as Figure 6 As shown in FIG. 1 , in the comparative example, multiple ripples are generated between the resonant frequency and the anti-resonant frequency. Specifically, multiple ripples are generated around 1950 MHz to 2000 MHz. These ripples are caused by the transverse mode. In contrast, it can be seen that in the first embodiment, the ripples caused by the transverse mode are suppressed. Figure 7 As shown, it can be seen that in the first embodiment, the unnecessary waves outside the passband are suppressed compared with the comparative example. Specifically, in the first embodiment, the unnecessary waves are suppressed on both the low frequency side of the resonant frequency and the high frequency side of the anti-resonant frequency. As described above, in the first embodiment, the unnecessary waves outside the passband can be suppressed, and the transverse mode can be suppressed.

[0110] In the present invention, the above-mentioned effects are obtained by utilizing the fact that propagation characteristics of elastic waves differ in the respective excitation parts. The details are described below.

[0111] The phase velocity of the elastic wave has a dependency on the excitation angle in each curve region, and shows a characteristic inherent to the structure of the substrate. In addition, the inverse of the phase velocity is equivalent to the inverse velocity surface. Therefore, the excitation angle θ C1_prop and the excitation angle θ C2_propThe relationship between the phase velocity and the reverse velocity surface of the piezoelectric substrate is roughly equal. Thus, an example of the reverse velocity surface of a piezoelectric substrate with different layer structures is shown. One piezoelectric substrate is a substrate that includes only LiTaO3 (LT) that is rotated Y-cut 42°X propagation. This substrate is set as the first piezoelectric substrate. The other piezoelectric substrate is a bonded substrate of a piezoelectric layer / support substrate. This substrate is set as the second piezoelectric substrate. More specifically, the second piezoelectric substrate is a substrate on which a silicon substrate with a surface orientation of (100), a silicon oxide film, and a lithium tantalate layer are stacked in sequence. Even if the surface orientation of the silicon substrate is other surface orientations such as (110) or (111), the concave and convex shape of the reverse velocity surface will not change.

[0112] Figure 8 It is a diagram showing the inverse velocity surface of the elastic wave propagating through the first piezoelectric substrate and the second piezoelectric substrate.

[0113] Figure 8 The x-axis shown corresponds to the result when it is parallel to the propagation axis. That is, it corresponds to the excitation angle θ C1_prop and the excitation angle θ C2_prop The result when the angle of the first piezoelectric substrate and the second piezoelectric substrate are both linearly symmetrical with the x-axis as the axis of symmetry. The reciprocal velocity surface in the first piezoelectric substrate is concave. On the other hand, the reciprocal velocity surface in the second piezoelectric substrate is convex. Thus, it can be seen that the elastic wave propagating in the substrate has a linear symmetry with respect to the excitation angle θ. C1_prop and the excitation angle θ C2_prop The dependence of varies depending on the structure of the substrate. In addition, when the elastic wave mode is different, the excitation angle θ in the same substrate C1_prop and the excitation angle θ C2_prop The dependencies are different. This is due to Fig. 9 Shown.

[0114] Fig. 9 It is a diagram showing the inverse velocity surfaces of the longitudinal wave, the fast transverse wave, and the slow transverse wave in the first piezoelectric substrate.

[0115] like Fig. 9 As shown, the inverse velocity surfaces of the three elastic wave modes, namely the longitudinal wave, the fast shear wave and the slow shear wave, are different from each other. Fig. 9 The portions passing through arrows L1 and L2 correspond to the excitation angles θ C1_prop and the excitation angle θ C2_propAn example of the result for a case other than 0°. The interval between the inverse velocity surfaces of the slow shear wave and the fast shear wave in the portion passing through arrow L1 is different from the interval between the inverse velocity surfaces of the slow shear wave and the fast shear wave in the portion passing through arrow L2. Similarly, the interval between the inverse velocity surfaces of the fast shear wave and the longitudinal wave in the portion passing through arrow L1 is different from the interval between the inverse velocity surfaces of the fast shear wave and the longitudinal wave in the portion passing through arrow L2. That is, in each curve region, in the excitation portions having different excitation angles, the intervals between the inverse velocity surfaces of different modes are different. This is also the case in the relationship between the main mode and the useless wave used in the elastic wave device.

[0116] In this case, in the elastic wave device 1 of the first embodiment, the resonant frequencies of the main modes or the antiresonant frequencies are made substantially consistent in all the excitation parts. Therefore, the frequencies of the unnecessary waves in different excitation parts become different from each other. As a result, the unnecessary waves and transverse modes outside the passband are dispersed. Therefore, the unnecessary waves and transverse modes outside the passband can be suppressed.

[0117] In the first embodiment, since the resonant frequencies or anti-resonant frequencies in the respective excitation parts are substantially consistent with each other, the main mode is preferably excited. Figure 5 As shown in FIG. 1 , the impedance ratio in the first embodiment is the same as the impedance ratio in the comparative example. In this way, it is possible to suppress degradation of the resonance characteristics.

[0118] Moreover, if Figure 3 As shown in the figure, in the first embodiment, the intersection region D includes the first curved region W1 and the second curved region W2. Thus, the intersection angle can be effectively increased at any position of the elastic wave device 1. More specifically, each electrode finger includes a portion located in the first curved region W1 and a portion located in the second curved region W2. Therefore, the intersection angle in the portion where each electrode finger is located is equivalent to the intersection angle θ in the first curved region W1. C1_AP and the intersection angle θ in the second curve area W2 C2_AP Therefore, at any position in the intersection region D, the range of the excitation angle is wide. As a result, it is possible to effectively disperse the unnecessary waves and transverse modes outside the passband.

[0119] The following describes in more detail the case where the resonant frequencies of the main modes are made substantially consistent. As described above, the phase velocity is equivalent to the inverse of the inverse velocity surface. Therefore, the excitation angle θ C1_prop and the excitation angle θ C2_prop The relationship between the phase velocity and Fig. 9 The inverse velocity surface in the XY plane of the piezoelectric substrate shown in FIG. 1 is approximately equal. That is, the function representing the curved shape of the electrode finger can be said to be determined by the shape of the inverse velocity surface in the XY plane of the piezoelectric substrate. The phase velocity of the elastic wave has a constant with respect to the excitation angle θ.C1_prop and the excitation angle θ C2_prop dependency.

[0120] However, if the electrode fingers are simply shaped into a curve, the impedance frequency characteristic becomes C1_prop and the excitation angle θ C2_prop The impedance frequency characteristic is an impedance frequency characteristic in which the characteristics of the resonance frequencies in the MOSFET are greatly different from each other. Therefore, the impedance frequency characteristic is greatly deteriorated. Therefore, in the first embodiment, the duty ratio affecting the frequency is adjusted according to the excitation angle θ. C1_prop and the excitation angle θ C2_prop Thus, each excitation angle θ can be changed. C1_prop and the excitation angle θ C2_prop The frequencies of the elastic waves excited in the circuit are roughly consistent. Therefore, in each excitation unit, the resonant frequencies can be roughly consistent with each other. In addition, in each excitation unit, the anti-resonant frequencies can also be roughly consistent with each other. Therefore, the impedance frequency characteristic is formed in which the resonant frequency or the anti-resonant frequency is roughly consistent.

[0121] Depend on Fig.10 The excitation angle θ in the first embodiment is shown. C1_prop In addition, examples in which the maximum value of the duty ratio is different from that of the first embodiment are also shown as first and second modified examples of the first embodiment.

[0122] Fig.10 is an absolute value of the excitation angle |θ of the IDT electrode in the first embodiment, the first modification, and the second modification. C1_prop |A graph showing the relationship between 0 and duty cycle.

[0123] In the first embodiment, at the excitation angle θ C1_prop When the excitation angle θ is 0°, the duty ratio is set to the maximum value. C1_prop When the excitation angle is 0°, the duty cycle is 0.5. C1_prop The larger | is, the smaller the duty ratio is. Thus, in all the excitation parts in the first curve region, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0124] In the first and second modified examples, the absolute value of the excitation angle |θ C1_prop | is larger, the duty ratio is smaller. In the first modification, at the excitation angle θ C1_prop When the excitation angle θ is 0°, the duty ratio is 0.64. C1_propWhen the duty ratio is 0°, the duty ratio is 0.425. In the first variant and the second variant, the resonant frequencies or anti-resonant frequencies of all the excitation parts in the first curve region are substantially consistent with each other. In addition, in the first embodiment, the first variant and the second variant, the absolute value of the excitation angle in the second curve region |θ C2_prop The relationship between | and duty cycle is also set to Fig.10 Therefore, in all the excitation parts in the second curve region, the resonant frequencies or the anti-resonant frequencies are substantially consistent with each other.

[0125] In addition, in the first modification and the second modification, the configuration is the same as that of the first embodiment except for the duty ratio. Therefore, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0126] When forming the IDT electrode 8, for example, semiconductor photolithography is used. When using semiconductor photolithography to form a resist and metal wiring pattern, if the duty ratio is less than 0.2 or greater than 0.8, pattern formation becomes difficult, and stable pattern processing with small deviation becomes difficult. Fig.10 , excitation angle θ C1_prop The larger the duty cycle when the excitation angle is 0°, the greater the absolute value of the excitation angle |θ C1_prop | becomes larger. That is, θ C1_prop The larger the duty ratio when it is 0°, the greater the absolute value of the excitation angle |θ C1_prop |The larger the curve pattern. For the absolute value of the excitation angle |θ C1_prop | The curve pattern in a larger range can further improve the effect of suppressing unnecessary waves. Therefore, the duty ratio of the electrode fingers of the IDT electrode 8 is preferably set in the range of 0.2 to 0.8, and more preferably in the range of 0.25 to 0.75. C1_prop The duty ratio at 0° is preferably set to 0.5 rather than 0.425, and more preferably set to 0.64 rather than 0.5.

[0127] In addition, the relationship between the duty ratio and the frequency of each mode varies depending on the reverse velocity surface of the piezoelectric substrate. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the excitation angle |θ C1_prop | and |θ C2_prop | The larger the duty ratio, the larger the duty ratio. In all the excitation parts, the resonant frequencies or anti-resonant frequencies may be roughly the same. As an example, an elastic wave device in which an IDT electrode provided on a substrate including only LiNbO3 that rotates Y-cut -4°X propagates is embedded in a thick SiO2 film can be cited. Alternatively, at the excitation angle θ where the reference line N passes, C1_prop and the excitation angle θC2_prop In the excitation portion at 0°, the duty ratio is not necessarily the maximum or minimum.

[0128] In the first embodiment, the loss below the resonance frequency can be reduced. This effect is shown by comparing the first embodiment and the reference example. In the reference example, Fig.11 As shown in the schematic diagram, the shape of the IDT electrode 218 when viewed from above is roughly fan-shaped, and is linearly symmetrical with the reference line N as the symmetry axis. The shape of each electrode finger when viewed from above in the reference example is a single arc shape. Therefore, there is only one fixed point in the reference example. The reference line N in the reference example passes through the center of the intersection area and the fixed point.

[0129] The design parameters of the elastic wave device 1 of the first embodiment according to the comparison are the same as those of the first embodiment except for the following points. Figure 5 to Figure 7 The design parameters of the elastic wave device 1 involved in the comparison are the same.

[0130] Number of pairs of electrode fingers of IDT electrode 8: 90 pairs

[0131] Crossing angle θ C1_AP : 10°

[0132] Crossing angle θ C2_AP : 10°

[0133] Duty cycle: At the excitation angle θ C1_prop and the excitation angle θ C1_prop The excitation part with a 0° angle is 0.64

[0134] The design parameters of the reference example are also the same as those of the elastic wave device 1 of the first embodiment of the comparison. In the reference example, the crossing angle θ is C1_AP The angle is equivalent to the angle formed by the reference line N and the edge of the intersection region on the side of one bus bar. C2_AP This corresponds to the angle formed by the reference line N and the edge portion on the other busbar side of the intersection region. In the reference example, the duty ratio is also adjusted so that the resonant frequency or antiresonant frequency is substantially the same in all the excitation parts in the intersection region.

[0135] Fig.12 It is a diagram showing the return loss in the first embodiment and the reference example. Fig.13 It is a graph showing the impedance frequency characteristics in the first embodiment and the reference example. Fig.14 It is a diagram showing the phase characteristics in the first embodiment and the reference example.

[0136] like Fig.12As shown, at least in the vicinity of the frequency indicated by the arrow R, the absolute value of the return loss in the first embodiment becomes smaller than the absolute value of the return loss in the reference example. In addition, the resonant frequency of the elastic wave device in the first embodiment and the reference example is near 1940 MHz, and the anti-resonant frequency is near 2010 MHz. Thus, it can be seen that in the first embodiment, the loss below the resonant frequency can be reduced. Furthermore, in the first embodiment, the loss can be reduced in the frequency band between the resonant frequency and the anti-resonant frequency.

[0137] like Fig.13 As shown in FIG. 1 , the impedance ratio in the first embodiment is the same as the impedance ratio in the reference example. Furthermore, the fractional bandwidth in the first embodiment is also the same as the fractional bandwidth in the reference example. In addition, when the resonant frequency is fr and the antiresonant frequency is fa, the fractional bandwidth is represented by |fa-fr| / fr. Fig.14 As shown, in both the first embodiment and the reference example, it is possible to suppress unnecessary waves outside the passband.

[0138] Back to Figure 1 The shapes of the plurality of first offset electrodes 18 in the first embodiment correspond to the shapes of the arcs of the plurality of concentric circles. The center of the circle including the arcs of the shapes of the plurality of first offset electrodes 18 is Figure 3 In the first curve region W1, when the shape of the plurality of electrode fingers in a plan view is an elliptical arc shape, the shape of the plurality of first offset electrodes 18 may be an elliptical arc shape included in an ellipse with the fixed point C1 as the center of gravity. In the IDT electrode 8, in the region between the first curve region W1 and the first bus bar 14, the duty ratio changes similarly to the first curve region W1. More specifically, in the first embodiment, in the region between the first bus bar 14 and the intersection region D, the closer to the first bus bar 14, the smaller the duty ratio becomes.

[0139] Similarly, the shapes of the plurality of second offset electrodes 19 are also shapes corresponding to the shapes of the arcs in the plurality of concentric circles. The center of the circle including the arcs in the shapes of the plurality of second offset electrodes 19 coincides with the fixed point C2. In addition, in the second curve region W2, when the shapes of the plurality of electrode fingers in a plan view are the shapes of elliptical arcs, the shapes of the plurality of second offset electrodes 19 may be the shapes of elliptical arcs included in the ellipse with the fixed point C2 as the center of gravity. In the IDT electrode 8, in the region between the second curve region W2 and the second bus bar 15, the duty ratio changes in the same manner as in the second curve region W2. More specifically, in the first embodiment, in the region between the second bus bar 15 and the intersection region D, the closer to the second bus bar 15, the smaller the duty ratio becomes.

[0140] In addition, the shapes of the plurality of first offset electrodes 18 and the plurality of second offset electrodes 19 are not limited to the above. For example, in the area between the first bus bar 14 and the intersection area D, the closer to the first bus bar 14, the larger the duty ratio. In the area between the second bus bar 15 and the intersection area D, the closer to the second bus bar 15, the larger the duty ratio. Alternatively, the offset electrodes may not necessarily be provided. In this case, in the present invention, useless waves can also be suppressed. Furthermore, the shapes of the first electrode fingers 16 and the second electrode fingers 17 are not particularly limited in areas other than the intersection area D.

[0141] As described above, the top end of the second electrode finger 17 and the top end of the first offset electrode 18 are opposed to each other with the gap g1 therebetween. The size of the gap g1 is the distance between the top end of the second electrode finger 17 and the top end of the first offset electrode 18. Similarly, the size of the gap g2 is the distance between the top end of the first electrode finger 16 and the top end of the second offset electrode 19. The sizes of the gap g1 and the gap g2 are preferably less than 1λ, and more preferably less than 0.5λ. If the gap g1 is larger than 0.5λ, there is a tendency for the elastic wave to easily leak in the direction from the intersection area D toward the first bus bar 14. The same is true when the gap g2 is larger than 0.5λ. If the sizes of the gap g1 and the gap g2 exceed 1λ, the amount of main mode leakage increases, and sometimes the loss cannot be ignored.

[0142] In addition, the length of the first offset electrode 18 and the second offset electrode 19 is preferably 1λ or more, and more preferably 1.3λ or more. If the length of the first offset electrode 18 is shorter than 1.3λ, there is a tendency that the elastic wave becomes easy to leak in the direction from the intersection area D toward the first bus bar 14. The same is true when the length of the second offset electrode 19 is shorter than 1.3λ. If the length of the first offset electrode 18 and the second offset electrode 19 is shorter than 1λ, the amount of main mode leakage increases, and the loss may become non-negligible.

[0143] In addition, if Figure 2 As shown, in the first embodiment, the piezoelectric substrate 2 is a stacked substrate of a supporting substrate 4, a first layer 5a and a second layer 5b of an intermediate layer 5, and a piezoelectric layer 6. More specifically, the first layer 5a in the first embodiment is a high-acoustic-velocity film. The high-acoustic-velocity film is a layer with a relatively high-acoustic-velocity. More specifically, the sound velocity of the body wave propagating in the high-acoustic-velocity film is higher than the sound velocity of the elastic wave propagating in the piezoelectric layer 6. On the other hand, the second layer 5b is a low-acoustic-velocity film. The low-acoustic-velocity film is a film with a relatively low-acoustic-velocity. More specifically, the sound velocity of the body wave propagating in the low-acoustic-velocity film is lower than the sound velocity of the body wave propagating in the piezoelectric layer 6.

[0144] In the first embodiment, the high-acoustic-velocity film, the low-acoustic-velocity film, and the piezoelectric layer 6 are sequentially stacked on the piezoelectric substrate 2. This allows the energy of the elastic wave to be effectively confined in the piezoelectric layer 6.

[0145] As materials for the high acoustic velocity membrane, for example, silicon, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconium oxide, cordierite, mullite, steatite, forsterite, magnesium oxide, DLC (diamond-like carbon) film, diamond, spinel or sialon, etc., and media with the above materials as the main components can be used.

[0146] As the material of the low acoustic velocity film, for example, a material mainly composed of glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum pentoxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide can be used.

[0147] As a material for the piezoelectric layer 6 , for example, lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate) can be used. As a material for the piezoelectric layer 6 , lithium tantalate or lithium niobate is preferably used.

[0148] As the material of the support substrate 4, for example, piezoelectrics such as aluminum nitride, lithium tantalate, lithium niobate, quartz, alumina, sapphire, magnesium oxide, silicon nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, spinel, ceramics such as sialon, dielectrics such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), diamond, or semiconductors such as silicon, or materials containing the above materials as the main component can also be used. In addition, the above-mentioned spinel listed as an example of the material of the support substrate 4 and the high acoustic velocity film includes aluminum compounds containing one or more elements selected from Mg, Fe, Zn, Mn, etc. and oxygen. As examples of the above-mentioned spinel, MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4 can be listed. As the material of the support substrate 4, silicon is preferably used.

[0149] In this specification, the main component refers to a component that accounts for more than 50% by weight. The material of the main component may be in any state of single crystal, polycrystalline, or amorphous, or in a state of a mixture of these.

[0150] In addition, the relationship between the acoustic velocities in the first layer 5a and the second layer 5b in the intermediate layer 5 is not limited to the above. Furthermore, the layer structure of the piezoelectric substrate 2 is not limited to the above. The third and fourth variants of the first embodiment are shown below, in which only the structure of the piezoelectric substrate 2 is different from that of the first embodiment. In the third and fourth variants, as in the first embodiment, it is possible to suppress unnecessary waves and transverse modes outside the passband. Furthermore, it is possible to effectively confine the energy of the elastic wave on the piezoelectric layer 6 side.

[0151] exist Fig.15 In the third variation shown, the piezoelectric substrate 2A includes a support substrate 4, an acoustic reflection film 7, an intermediate layer 5A, and a piezoelectric layer 6. The acoustic reflection film 7 is provided on the support substrate 4. The intermediate layer 5A is provided on the acoustic reflection film 7. The piezoelectric layer 6 is provided on the intermediate layer 5A. The intermediate layer 5A is a low acoustic velocity film.

[0152] The acoustic reflection film 7 is a laminate of multiple acoustic impedance layers. Specifically, the acoustic reflection film 7 has multiple low acoustic impedance layers and multiple high acoustic impedance layers. The high acoustic impedance layer is a layer with relatively high acoustic impedance. More specifically, the multiple high acoustic impedance layers of the acoustic reflection film 7 are the high acoustic impedance layer 13a, the high acoustic impedance layer 13b, and the high acoustic impedance layer 13c. On the other hand, the low acoustic impedance layer is a layer with relatively low acoustic impedance. More specifically, the multiple low acoustic impedance layers of the acoustic reflection film 7 are the low acoustic impedance layer 12a and the low acoustic impedance layer 12b. The low acoustic impedance layers and the high acoustic impedance layers are alternately laminated. In addition, the high acoustic impedance layer 13a is the layer located closest to the piezoelectric layer 6 in the acoustic reflection film 7.

[0153] The acoustic reflective film 7 has two low acoustic impedance layers and three high acoustic impedance layers. However, the acoustic reflective film 7 only needs to have at least one low acoustic impedance layer and at least one high acoustic impedance layer.

[0154] As the material of the low acoustic impedance layer, for example, silicon oxide or aluminum can be used. As the material of the high acoustic impedance layer, for example, metals such as platinum or tungsten, and dielectrics such as aluminum nitride or silicon nitride can be used. In addition, the material of the intermediate layer 5A can also be the same as that of the low acoustic impedance layer.

[0155] exist Fig.16 In the fourth variant shown, the piezoelectric substrate 2B has a supporting substrate 4B and a piezoelectric layer 6. The piezoelectric layer 6 is directly provided on the supporting substrate 4B. More specifically, the supporting substrate 4B has a recess 4c. The piezoelectric layer 6 is provided on the supporting substrate 4B so as to block the recess 4c. Thus, a hollow portion is provided in the piezoelectric substrate 2B. In a plan view, the hollow portion overlaps with at least a portion of the IDT electrode 8.

[0156] In the first embodiment, the duty cycle is changed in each curve region according to the excitation angle, so that the resonant frequencies or anti-resonant frequencies of all the excitation parts are roughly consistent with each other. However, it is not limited to this. As long as the excitation part is closer to the first envelope E1 or the second envelope E2, the value of at least one of the duty cycle, the electrode finger spacing, and the thickness of the plurality of first electrode fingers 16 and the plurality of second electrode fingers 17 changes in one of the directions of increasing and decreasing. Alternatively, parameters such as the thickness of the intermediate layer in the piezoelectric substrate that affects the frequency can also be changed in each curve region according to the excitation angle. In the case where a dielectric film is provided on the piezoelectric substrate so as to cover the IDT electrode, the thickness of the dielectric film can also be changed in each curve region according to the excitation angle. It is also possible to change multiple parameters among the above parameters in each curve region according to the excitation angle. In these cases, it is also possible to make the resonant frequencies or anti-resonant frequencies roughly consistent with each other in all the excitation parts.

[0157] Alternatively, the parameters including the duty ratio of the offset electrode, the center-to-center distance between the offset electrode and the electrode finger, and the thickness of the offset electrode may be changed in the same manner as the parameters of the electrode finger in the excitation portion.

[0158] The following describes examples in which parameters other than the duty ratio are changed in accordance with the excitation angle in each curve region. In each of the following examples, the shape of the reflector is different from that of the first embodiment because the shape of the IDT electrode is different from that of the first embodiment.

[0159] Fig.17 It is a schematic plan view of an elastic wave device according to a second embodiment.

[0160] The present embodiment differs from the first embodiment in that the shape of the plurality of electrode fingers in a plan view is an elliptical arc shape. The present embodiment also differs from the first embodiment in that the duty cycle is fixed and the electrode finger pitch is not fixed in the IDT electrode 28. Except for the above aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0161] The shape of the plurality of electrode fingers when viewed from above is a shape formed by connecting two elliptical arcs. Fig.18 As shown, in this embodiment, the intersection region D also has a first curved region W1 and a second curved region W2. In the first curved region W1, the shapes of the plurality of electrode fingers in a plan view are shapes of elliptical arcs corresponding to a plurality of ellipses whose centers of gravity are at the same position. In more detail, Fig.18 The midpoint between the focus A1 and the focus B1 shown is the center of gravity. And, this center of gravity is the fixed point C1. The same is true in the second curve area W2. And, the center of gravity between the focus A2 and the focus B2 is the fixed point C2.

[0162] In the present embodiment, regarding α12 / α11 and α22 / α21 of the ellipticity coefficients α1 / α2 of the shape of the plurality of electrode fingers in a plan view, α12 / α11<1 and α22 / α21<1. More specifically, α12 / α11=α22 / α21=0.72. However, the ellipticity coefficients α12 / α11 and α22 / α21 are not limited to the above.

[0163] As described above, the duty ratio is fixed in the IDT electrode 28. Specifically, the duty ratio is 0.5. In the first curve region W1, the absolute value of the excitation angle |θ C1_prop The larger | is, the narrower the electrode finger pitch is. In the second curve region W2, the absolute value of the excitation angle |θ C2_prop The larger the | is, the narrower the electrode finger pitch is. As a result, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other in all the excitation parts. The absolute value of the excitation angle |θ is specifically shown below. C1_prop | and the electrode finger pitch. Here, the excitation angle θ C1_prop The electrode finger pitch in the excitation portion at 0° is defined as p0, the electrode finger pitch in an arbitrary portion is defined as p1, and {(p1-p0) / p0}×100[%] is defined as the electrode finger pitch change rate Δpitch[%].

[0164] Fig.19 is an absolute value of the excitation angle |θ of the IDT electrode in the second embodiment. C1_prop |A graph showing the relationship between Δpitch and the rate of change of the electrode finger pitch.

[0165] like Fig.19 As shown, in this embodiment, the excitation angle θ in the IDT electrode 28 is C1_prop In the excitation section with a value of 0°, Δpitch is 0%. C1_prop |The larger the value, the more negative Δpitch becomes. That is, the absolute value of the excitation angle |θ C1_prop The larger |θ is, the narrower the electrode finger pitch is. In addition, in the present embodiment, the absolute value of the excitation angle in the second curve region W2 |θ C2_prop The relationship between | and Δpitch is also set to Fig.19 The relationship shown is the same. Accordingly, in all the excitation parts in the first curve area W1 and the second curve area W2, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other. Moreover, as in the first embodiment, the unnecessary waves and transverse modes outside the passband can be dispersed, and the unnecessary waves and transverse modes outside the passband can be suppressed.

[0166] Furthermore, an example of design parameters of the elastic wave device according to the present embodiment is shown below.

[0167] Ellipticity coefficient of electrode finger shape α12 / α11: 0.72

[0168] Ellipticity coefficient of electrode finger shape α22 / α21: 0.72

[0169] Crossing angle θ C1_AP : 7.5°

[0170] Crossing angle θ C2_AP : 7.5°

[0171] The longest wavelength λ: 2μm

[0172] Electrode finger spacing: at excitation angle θ C1_prop and the excitation angle θ C1_prop 1μm in the excitation part at 0°

[0173] Duty cycle: 0.5

[0174] Bus bar inclination angle of the 1st bus bar and the 2nd bus bar: 7.5°

[0175] Length of the first offset electrode and the second offset electrode: 3.5λ

[0176] In addition, the relationship between the electrode finger pitch and the frequency of each mode varies depending on the reciprocal velocity surface of the piezoelectric substrate. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the excitation angle |θ C1_prop | and |θ C2_prop | When the electrode finger pitch is wider, the resonant frequencies or anti-resonant frequencies of all the excitation parts may be roughly the same. As an example, an elastic wave device in which an IDT electrode provided on a substrate including only a rotating Y-cut -4°X-propagated LiNbO3 is embedded in a thick SiO2 film can be cited. Alternatively, at the excitation angle θ passing through the reference line N C1_prop and the excitation angle θ C2_prop In the excitation portion with an angle of 0°, the value of the electrode finger pitch is not necessarily the maximum or the minimum.

[0177] Fig. 20 It is a schematic plan view showing the vicinity of the gap on the first bus bar side of the IDT electrode in the third embodiment.

[0178] This embodiment differs from the first embodiment in that the duty ratio is constant in the region between the intersection region and the first bus bar 14 and in the region between the intersection region and the second bus bar. Except for the above, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0179] The duty ratio in the region between the intersection region and the first bus bar 14 is the same as the duty ratio in the portion where the top ends of the plurality of second electrode fingers 17 are arranged. The widths of the plurality of first offset electrodes 38 are fixed. The widths of the plurality of first electrode fingers 16 are also fixed in the region outside the intersection region. More specifically, the widths of the plurality of first offset electrodes 38 are the same as the widths of the top ends of the plurality of second electrode fingers 17. Furthermore, the widths of the plurality of first electrode fingers 16 are the same as the widths of the plurality of first offset electrodes 38 in the region outside the intersection region. In addition, the shape of the plurality of first offset electrodes 38 when viewed from above is curved. The shape of the plurality of first electrode fingers 16 in the region outside the intersection region when viewed from above is also curved.

[0180] Although not shown in the figure, the duty ratio in the region between the intersection region and the second bus bar is the same as the duty ratio in the portion where the top ends of the plurality of first electrode fingers 16 are arranged. The width of the plurality of second offset electrodes is the same as the width of the top ends of the plurality of first electrode fingers 16 and is constant. The width of the plurality of second electrode fingers 17 is the same as the width of the plurality of second offset electrodes in the region outside the intersection region. The shape of the plurality of second offset electrodes in a plan view is a curve. The shape of the plurality of second electrode fingers 17 in the region outside the intersection region in a plan view is also a curve.

[0181] In the present embodiment, the widths of the plurality of first offset electrodes 38 and the plurality of first electrode fingers 16 do not become narrower in the intersection region and the region between the first bus bars 14. The widths of the plurality of second offset electrodes and the plurality of second electrode fingers 17 do not become narrower in the intersection region and the region between the second bus bars. This can reduce the series resistance.

[0182] Moreover, in this embodiment, similarly to the first embodiment, the intersection region includes a plurality of curve regions, and the closer the excitation portion is to the first envelope or the second envelope, the smaller the duty cycle is. Accordingly, the resonant frequency or anti-resonant frequency can be made substantially consistent in all the excitation portions, and the unnecessary waves and transverse modes outside the passband can be suppressed.

[0183] The following shows a first variant and a second variant of the third embodiment in which the structures of only the region between the intersection region and the first bus bar 14 and the region between the intersection region and the second bus bar are different from those of the third embodiment. In the first variant and the second variant, as in the third embodiment, the resonant frequency or the anti-resonant frequency can be made substantially consistent in all the excitation parts, the unnecessary waves and the transverse mode outside the passband can be suppressed, and the series resistance can be reduced.

[0184] exist Fig.21In the first modified example shown, the width of the plurality of first offset electrodes 38A is wider than the width of the top end portions of the plurality of second electrode fingers 37A. The width of the plurality of first electrode fingers 36A is the same as the width of the plurality of first offset electrodes 38A in the region outside the intersection region. Although not shown, the width of the plurality of second offset electrodes is wider than the width of the top end portions of the plurality of first electrode fingers 36A. The width of the plurality of second electrode fingers 37A is the same as the width of the plurality of second offset electrodes in the region outside the intersection region.

[0185] Therefore, in this variation, the duty ratio in the region between the intersection region and the first bus bar 14 is greater than the duty ratio in the portion where the top ends of the plurality of second electrode fingers 37A are arranged. Similarly, the duty ratio in the region between the intersection region and the second bus bar is greater than the duty ratio in the portion where the top ends of the plurality of first electrode fingers 36A are arranged.

[0186] exist Fig. 22 In the second modification shown, the first offset electrodes 38B and the second offset electrodes are linear in plan view. Similarly, in this modification, the first electrode fingers 36B and the second electrode fingers 37B are linear in plan view in the region outside the intersection region.

[0187] Fig.23 It is a schematic plan view of an elastic wave device according to a fourth embodiment.

[0188] The present embodiment differs from the first embodiment in that the plurality of electrode fingers of the IDT electrode 48 include a linear portion. The present embodiment also differs from the first embodiment in that there are two reference lines N1 and a reference line N2. More specifically, the reference line N1 is a reference line in the first curve region W1. The reference line N2 is a reference line in the second curve region W2. Except for the above aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0189] The intersection region of the IDT electrode 48 includes a first curved region W1, a second curved region W2, and a straight region T. The first curved region W1, the second curved region W2, and the straight region T are arranged in a direction in which the first bus bar 14 and the second bus bar 15 are opposed to each other. More specifically, the first curved region W1 and the second curved region W2 are opposed to each other with the straight region T interposed therebetween.

[0190] In the IDT electrode 48, each electrode finger has two inflection points. Each inflection point is a point connecting an arc and a straight line. The extension line of the boundary line of the straight line region T and the first curve region W1 passes through the fixed point C1. The straight line including the boundary line and the extension line of the boundary line is the reference line N1 in the first curve region W1. The angle θ in the first curve region W1 is C1is the angle formed by the straight line passing through the fixed point C1 and the excitation part in the first curve region W1 and the reference line N1. C1 =θ C1_prop On the other hand, the extension line of the boundary line between the straight area T and the second curved area W2 passes through the fixed point C2. The straight line including the boundary line and the extension line of the boundary line is the reference line N2 in the second curved area W2. The angle θ in the second curved area W2 is C2 is the angle formed by the straight line passing through the fixed point C2 and the excitation part in the second curve area W2 and the reference line N2. C2 =θ C2_prop .

[0191] The excitation angle is constant in the straight region T. More specifically, at the boundary between the straight region T and the first curved region W1, the excitation angle θ is constant. C1_prop Similarly, at the boundary between the straight line region T and the second curved region W2, the excitation angle θ C2_prop Therefore, the excitation angle of the excitation portion in the straight region T is equivalent to 0°. In addition, the excitation angle of the excitation portion in the straight region T does not necessarily have to be 0°.

[0192] In this embodiment, the X propagation direction, which is the direction in which the propagation axis of the piezoelectric layer 6 extends, is orthogonal to the direction in which the plurality of electrode fingers extend in the entire straight region T. Therefore, the straight region T is a region that is stable with respect to the propagation axis. By having the straight region T in the intersection region, the change in the propagation direction can be reduced as a whole for the IDT electrode 48, and the propagation of the elastic wave can be stabilized.

[0193] In addition, in this embodiment, as in the first embodiment, the intersection region includes a plurality of curve regions, and the duty ratio is smaller as the excitation portion is closer to the first envelope E1 or the second envelope E2. Thus, the resonant frequency or anti-resonant frequency can be made substantially consistent in all the excitation portions, and unnecessary waves and transverse modes outside the passband can be suppressed.

[0194] In addition, the reference line in each curve region may be a straight line including the first envelope or the second envelope. This example is shown in the fifth embodiment.

[0195] Fig.24 is a schematic top view for explaining the structure of the IDT electrode in the fifth embodiment. Fig.24 In the figure, the hatching indicates the area of ​​each curve.

[0196] The difference between this embodiment and the first embodiment is that there are two reference lines N1 and reference line N2. The difference between this embodiment and the first embodiment is that the closer the excitation part is to the first envelope E1 or the second envelope E2, the larger the duty cycle. The difference between this embodiment and the first embodiment is that the shape of the plurality of electrode fingers in a plan view is a shape connecting two elliptical arcs. In addition to the above aspects, the elastic wave device of this embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0197] The extension line of the first envelope E1 passes through the fixed point C1. The straight line including the first envelope E1 and the extension line of the first envelope E1 is the reference line N1 in the first curve region W1. The angle formed by the straight line passing through the excitation portion in the first curve region W1 and the reference line N1 is the angle θ in the first curve region W1. C1 In addition, in the first envelope E1, the angle θ C1 is 0°.

[0198] On the other hand, the extension line of the second envelope E2 passes through the fixed point C2. The straight line including the second envelope E2 and the extension line of the second envelope E2 is the reference line N2 in the second curve area W2. The angle formed by the straight line passing through the excitation part in the second curve area W2 and the reference line N2 is the angle θ in the second curve area W2. C2 In addition, in the second envelope E2, the angle θ C2 is 0°.

[0199] The straight line passing through the fixed point C1 and the fixed point C2 includes the boundary line O between the first curved area W1 and the second curved area W2. In the IDT electrode 58, the intersection angle θ in the first curved area W1 is C1_AP is the angle formed by the straight line passing through the first envelope E1 and the fixed point C1 and the straight line passing through the boundary line O and the fixed point C1. On the other hand, the intersection angle θ in the second curve region W2 is C2_AP It is the angle formed by the straight line passing through the second envelope E2 and the fixed point C2 and the straight line passing through the boundary line O and the fixed point C2. However, the straight line passing through the fixed points C1 and C2 may not include the boundary line O between the first curve area W1 and the second curve area W2.

[0200] In this embodiment, as in the first embodiment, the duty ratio is determined according to the excitation angle θ. C1_prop The duty ratio changes so that the resonant frequencies or anti-resonant frequencies in all the excitation parts in the first curve region W1 are substantially consistent with each other. C2_propThe resonant frequencies or antiresonant frequencies of all the excitation parts in the second curve region W2 are changed so as to substantially match each other. Thus, the resonant frequencies or antiresonant frequencies of all the excitation parts can be substantially matched, and unnecessary waves and transverse modes outside the passband can be suppressed.

[0201] In addition, in the present invention, a structure that can utilize the piston mode can also be set. According to this, the energy of the main mode can be effectively confined on the central side of the intersection area, and the loss can be effectively reduced. Below, examples of structures that can utilize the piston mode are shown as the first to fourth modified examples of the fifth embodiment.

[0202] In addition, in the case of utilizing the piston mode structure, the portion of each curve region located on an arbitrary straight line passing through a fixed point in the region of the central region described later is set as an excitation portion. In the first to fourth variants, as in the fifth embodiment, the closer the excitation portion is to the first envelope or the second envelope, the greater the duty cycle. Accordingly, the resonant frequency or anti-resonant frequency can be made roughly consistent in all the excitation portions, and the useless waves and transverse modes outside the passband can be suppressed.

[0203] exist Fig.25 In the first variant shown in FIG. 1 , the first offset electrode and the second offset electrode are not provided. This is also true in other variants. In this variant, the plurality of first electrode fingers 56 have wide portions 56b. The plurality of second electrode fingers 57 also have wide portions 57a. More specifically, as Fig.26 As shown, the intersection region D of the IDT electrode 58A has a central region F and a pair of edge regions. Specifically, the pair of edge regions are a first edge region H1 and a second edge region H2. The first edge region H1 includes a first envelope E1 as an edge portion. The second edge region H2 includes a second envelope E2 as an edge portion. The first edge region H1 and the second edge region H2 are opposite to each other with the central region F sandwiched therebetween.

[0204] In the first edge region H1, wide width portions 57a are provided in the plurality of second electrode fingers 57. In the second edge region H2, wide width portions 56b are provided in the plurality of first electrode fingers 56. The width of the electrode finger in the wide width portion is wider than the width of the electrode finger in the central region F. By providing the wide width portion in each electrode finger, the speed of sound in the two edge regions is lower than the speed of sound in the central region F. In addition, the shape of the electrode finger in the edge region may be either a straight line or a curve. In addition, the shape of the wide width portion is not limited to a square shape, and may be a shape having a wide width portion in at least a portion.

[0205] The IDT electrode 58A has a pair of gap regions. Specifically, the pair of gap regions are a first gap region G1 and a second gap region G2. The first gap region G1 is located between the intersection region D and the first bus bar 14. The second gap region G2 is located between the intersection region D and the second bus bar 15.

[0206] As described above, the sound velocity in the first edge region H1 is lower than the sound velocity in the central region F. Thus, a low sound velocity region is formed in the first edge region H1. The so-called low sound velocity region is a region where the sound velocity is lower than the sound velocity in the central region F. Similarly, a low sound velocity region is also formed in the second edge region H2.

[0207] On the other hand, in the first gap region G1, only the first electrode finger 56 is provided among the first electrode finger 56 and the second electrode finger 57. Thus, a high sound velocity region is formed in the first gap region G1. The so-called high sound velocity region is a region where the sound velocity is higher than the sound velocity in the central region F. Similarly, a high sound velocity region is also formed in the second gap region G2.

[0208] In addition, a structure may be set as follows, that is, the frequency of the elastic wave propagating in the first edge region H1 is lower than the frequency of the elastic wave propagating in the central region F, and the frequency of the elastic wave propagating in the first edge region H1 and the frequency of the elastic wave propagating in the central region F are lower than the frequency of the elastic wave propagating in the first gap region G1. The frequency of the elastic wave propagating in the first gap region G1 is set to be a frequency when an elastic wave of a wavelength defined in the first edge region H1 is excited and the elastic wave propagates in the first gap region G1. When the direction in which the tangent of the electrode finger extends is in a range substantially consistent with the direction in which the tangent of the electrode finger in the first edge region H1 extends, the sound velocity of the central region F is defined. More specifically, the direction in which the tangent of the electrode finger extends is set to be a direction in which the angle formed by the direction and the direction in which the tangent of the electrode finger in the first edge region H1 extends is within a range of ±5° or less, and the sound velocity of the central region F is defined. The case where the frequency of the central region F is discussed is not limited to this.

[0209] In the present embodiment, the central region F, a pair of low sound velocity regions, and a pair of high sound velocity regions are arranged in this order from the inside to the outside in the direction in which the first bus bar 14 and the second bus bar 15 face each other.

[0210] In at least one of the first edge region H1 and the second edge region H2, at least one electrode finger among the plurality of electrode fingers may be provided with a wide portion. However, it is preferred that the wide portion be provided in a plurality of electrode fingers, and it is more preferred that the wide portion be provided in all electrode fingers. Thus, the piston mode can be established more reliably.

[0211] At least one of the first edge region H1 and the second edge region H2 may constitute a low sound velocity region. However, it is preferred that both the first edge region H1 and the second edge region H2 constitute a low sound velocity region. This allows the piston mode to be established more reliably.

[0212] In addition, in this modification, the case where the IDT electrode 58A has a pair of edge regions and the central region F is described. In addition, it is noted that the IDT electrodes of the fifth embodiment and other embodiments also have a pair of edge regions and the central region.

[0213] exist Fig. 27 In the second modification shown, one mass addition film 59A is provided in each of the first edge region H1 and the second edge region H2 , thereby forming a low sound velocity region in the first edge region H1 and the second edge region H2 .

[0214] More specifically, each mass-added film 59A has a strip shape. One of the pair of mass-added films 59A is provided over a plurality of electrode fingers in the first edge region H1. Similarly, the other mass-added film 59A is provided over a plurality of electrode fingers in the second edge region H2. Each mass-added film 59A is also provided in a portion between electrode fingers on the piezoelectric layer. As a material of the mass-added film 59A, an appropriate dielectric can be used.

[0215] In addition, the mass addition film 59A may be laminated on at least one of the plurality of electrode fingers in at least one of the first edge region H1 and the second edge region H2. However, it is preferred that the plurality of electrode fingers are laminated on the mass addition film 59A, and it is more preferred that all the electrode fingers are laminated on the mass addition film 59A. In this way, the piston mode can be established more reliably.

[0216] In this modification, the first electrode fingers 16 and the second electrode fingers 17 are configured similarly to those in the fifth embodiment. However, the first electrode fingers 16 and the second electrode fingers 17 may have wide portions similarly to the first modification.

[0217] exist Fig.28 In the third modification shown, a plurality of mass addition films 59B are provided in each of the first edge region H1 and the second edge region H2 , thereby forming low sound velocity regions in the first edge region H1 and the second edge region H2 .

[0218] More specifically, in this modification, the mass adding film 59B is provided only on one electrode finger. In this case, as the material of the mass adding film 59B, an appropriate metal or dielectric can be used.

[0219] In this modification, the first electrode fingers 16 and the second electrode fingers 17 are configured similarly to those in the fifth embodiment. However, the first electrode fingers 16 and the second electrode fingers 17 may have wide portions similarly to the first modification.

[0220] exist Fig.29 In the fourth modification shown, a high acoustic velocity film 52 is provided in the central region F of the IDT electrode 58 similar to the fifth embodiment. As a result, the acoustic velocity in the central region F is high. Therefore, the acoustic velocity in the first edge region H1 and the second edge region H2 is lower than the acoustic velocity in the central region F. That is, a low acoustic velocity region is formed in both the first edge region H1 and the second edge region H2.

[0221] In addition, in the structures of the first to third modified examples, the acoustic velocity increasing film 52 may also be provided in the central region F. As a material of the acoustic velocity increasing film 52 , for example, silicon nitride or the like can be used.

[0222] As described above, in the first to fourth variants, the duty cycle changes according to the excitation angle, similarly to the fifth embodiment. However, the structure using the piston mode is not limited to this. As long as the excitation portion is closer to the first envelope or the second envelope, the value of at least one of the duty cycle, the electrode finger pitch, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

[0223] Alternatively, parameters such as the thickness of the intermediate layer in the piezoelectric substrate that affect the frequency can also be changed in each curve area according to the excitation angle. In the case where a dielectric film is provided on the piezoelectric substrate so as to cover the IDT electrode, the thickness of the dielectric film can also be changed in each curve area according to the excitation angle. It is also possible to change multiple parameters among the above parameters in each curve area according to the excitation angle. In these cases, it is also possible to make the resonant frequencies or anti-resonant frequencies roughly consistent with each other in all the excitation parts.

[0224] Fig.30 It is a schematic plan view of an elastic wave device according to the sixth embodiment.

[0225] The present embodiment differs from the first embodiment in that the IDT electrode 68 has four curved regions. The present embodiment also differs from the first embodiment in that the first curved region W1 does not include the first envelope E1. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0226] The intersection region includes the third curve region W3 and the fourth curve region W4 in addition to the first curve region W1 and the second curve region W2. In the direction from the first envelope E1 toward the second envelope E2, the fourth curve region W4, the third curve region W3, the first curve region W1 and the second curve region W2 are arranged in sequence. The fourth curve region W4 includes the first envelope E1. On the other hand, the second curve region W2 includes the second envelope E2.

[0227] When the first and second curve regions W1 and W2 are defined as a first group of curve regions, and the third and fourth curve regions W3 and W4 are defined as a second group of curve regions, the first group of curve regions and the second group of curve regions have mutually inverted structures. Fig.30 The double-dotted dashed line in shows the boundary line and the extension line of the first curve area W1 and the third curve area W3. In the present embodiment, the boundary line is parallel to the first envelope E1 and the second envelope E2. However, the structural relationship of each curve area is not limited to the above. For example, in each curve area, the cross angle, the duty ratio in the excitation part with an excitation angle of 0°, the ellipticity coefficient and other parameters may also be different from each other.

[0228] The elastic wave device of this embodiment has two reference lines N1 and reference line N2. More specifically, the first group of curve regions is constructed in the same manner as the intersection region of the first embodiment. Therefore, the reference line N1 is common to the first curve region W1 and the second curve region W2. Similarly, the reference line N2 is also common to the third curve region W3 and the fourth curve region W4.

[0229] In this embodiment, the duty ratio also changes according to the excitation angle in each curve region. Thus, similarly to the first embodiment, the resonant frequencies or antiresonant frequencies of all excitation parts in all curve regions can be made substantially consistent, and unnecessary waves and transverse modes outside the passband can be suppressed.

[0230] Furthermore, since the intersection region includes four curved regions, standing waves are less likely to occur in the direction in which the first bus bar 14 and the second bus bar 15 face each other. Therefore, unnecessary waves outside the passband and transverse modes can be effectively suppressed.

[0231] Fig.31 It is a schematic plan view of an elastic wave device according to the seventh embodiment.

[0232] The present embodiment differs from the first embodiment in that the electrode finger pitch in the IDT electrode 78 is not constant and the ellipticity coefficient α2 / α1 is greater than 1. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment. In the present embodiment, both the duty ratio and the electrode finger pitch are not constant.

[0233] More specifically, in the present embodiment, in each of the first curve region W1 and the second curve region W2, the larger the absolute value of the excitation angle, the wider the electrode finger pitch. Moreover, the larger the absolute value of the excitation angle, the smaller the duty cycle. Accordingly, the resonant frequencies or anti-resonant frequencies can be made substantially consistent with each other in all the excitation parts. Furthermore, the unnecessary waves and transverse modes outside the passband can be dispersed, and the unnecessary waves and transverse modes outside the passband can be suppressed.

[0234] In the IDT electrode 78, both of α12 / α11 and α22 / α21 of the elliptic coefficients α2 / α1 in the shape of the plurality of electrode fingers are greater than 1. Accordingly, the response at the upper end of the stopband can be suppressed, and the value of the fractional stopband width can be increased. The details are described below. In addition, the so-called stopband is a region where the wavelength of the elastic wave becomes fixed by enclosing the elastic wave in a periodically structured metal grating. The so-called fractional stopband width is the value obtained by dividing the bandwidth of the stopband by the resonant frequency fr. The so-called upper end of the stopband is the end of the high-frequency side of the stopband. The bandwidth of the stopband is the difference between the frequency of the upper end of the stopband and the resonant frequency fr.

[0235] When the elliptic coefficient α2 / α1 is greater than 1, the frequency at the upper end of the stopband is dispersed. Thus, the frequency response at the upper end of the stopband can be suppressed. Moreover, the dimension of the intersection region along the direction in which the first bus bar 14 and the second bus bar 15 are opposite to each other becomes larger than the dimension of the intersection region along the direction orthogonal to the direction. Therefore, the curvature in the shape of the plurality of electrode fingers in a top view becomes close to 0. In this case, the bandwidth of the stopband becomes wider. Therefore, the value of the fractional stopband width can be increased. In addition, at least one of the elliptic coefficients α12 / α11 and α22 / α21 may be greater than 1.

[0236] Furthermore, in this embodiment, the fractional bandwidth can be increased compared to the case where the frequencies of the excitation parts are substantially matched with each other only by the duty ratio. When the resonant frequency is fr and the antiresonant frequency is fa, the fractional bandwidth is represented by |fr-fa| / fr.

[0237] An example of design parameters of the elastic wave device according to the present embodiment is shown below.

[0238] Number of pairs of IDT electrode fingers: 60 pairs

[0239] Ellipticity coefficient of electrode finger shape α12 / α11: 1.1

[0240] Ellipticity coefficient of electrode finger shape α22 / α21: 1.1

[0241] Crossing angle θ C1_AP : 10°

[0242] Crossing angle θ C2_AP : 10°

[0243] Duty cycle: At the excitation angle θ C1_prop and the excitation angle θ C2_prop 0.5 in the excitation section at 0°

[0244] Length of the first offset electrode and the second offset electrode: 3.5λ

[0245] Number of electrode fingers of reflector: 20 pairs

[0246] Fig.32 It is a schematic plan view of an elastic wave device according to the eighth embodiment.

[0247] The present embodiment differs from the first embodiment in that the electrode finger pitch in the IDT electrode 88 is not fixed and the ellipticity coefficient α2 / α1 is less than 1. Except for the above, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment. In the present embodiment, both the duty ratio and the electrode finger pitch are not fixed.

[0248] More specifically, in the present embodiment, in each of the first curve region W1 and the second curve region W2, the larger the absolute value of the excitation angle, the narrower the electrode finger pitch. Moreover, the larger the absolute value of the excitation angle, the smaller the duty cycle. Accordingly, the resonant frequencies or anti-resonant frequencies can be made substantially consistent with each other in all the excitation parts. Furthermore, the unnecessary waves and transverse modes outside the passband can be dispersed, and the unnecessary waves and transverse modes outside the passband can be suppressed.

[0249] In the IDT electrode 88 , both α12 / α11 and α22 / α21 of the ellipticity coefficients α2 / α1 of the shape of the plurality of electrode fingers in plan view are smaller than 1. This can suppress the response at the upper end of the stopband and increase the value of the fractional stopband width. The details are described below.

[0250] When the elliptic coefficient α2 / α1 is less than 1, the frequency at the upper end of the stop band is dispersed. Accordingly, the response of the frequency at the upper end of the stop band can be suppressed. Moreover, the dimension of the intersection region along the direction in which the first bus bar 14 and the second bus bar 15 are opposite to each other becomes smaller than the dimension of the intersection region along the direction orthogonal to the direction. Therefore, compared with the case where the shape of the plurality of electrode fingers when viewed from above is an arc shape, the curvature becomes larger. In this case, the interval between the frequency of the main mode and the frequency of the useless wave is widened. Therefore, the useless wave can be effectively suppressed. On the basis of the above structure, the frequencies of the respective excitation units are made substantially consistent with each other by both the duty cycle and the electrode finger spacing. Thus, the useless wave can be suppressed compared with the case where the frequencies of the respective excitation units are substantially consistent with each other only by the duty cycle. In addition, at least one of the elliptic coefficients α12 / α11 and α22 / α21 can be less than 1.

[0251] Furthermore, in the present embodiment, the value of the fractional bandwidth can be reduced compared to a case where the frequencies of the respective excitation parts are made substantially consistent with each other simply by the duty ratio.

[0252] An example of design parameters of the elastic wave device according to the present embodiment is shown below.

[0253] Number of pairs of IDT electrode fingers: 60 pairs

[0254] Ellipticity coefficient of electrode finger shape α12 / α11: 0.9

[0255] Ellipticity coefficient of electrode finger shape α22 / α21: 0.9

[0256] Crossing angle θ C1_AP : 10°

[0257] Crossing angle θ C2_AP : 10°

[0258] Duty cycle: At the excitation angle θ C1_prop and the excitation angle θ C2_prop 0.5 in the excitation section at 0°

[0259] Length of the first offset electrode and the second offset electrode: 3.5λ

[0260] Number of electrode fingers of reflector: 20 pairs

[0261] In the first to eighth embodiments, the duty ratio or the electrode finger pitch is adjusted so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly the same. However, the thickness of the plurality of electrode fingers may be adjusted so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are roughly the same. This example is shown in the ninth embodiment.

[0262] The ninth embodiment differs from the first embodiment in that the duty ratio of the IDT electrode is constant and the thickness of the plurality of electrode fingers is not constant. Except for the above points, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0263] Fig.33 is an absolute value of the excitation angle of the IDT electrode in the ninth embodiment |θ C1_prop |A diagram showing the relationship between the thickness of the electrode fingers.

[0264] like Fig.33 As shown, in the first curve region of the IDT electrode, the absolute value of the excitation angle |θ C1_prop | is larger, the thickness of the first electrode finger and the second electrode finger is thinner. In the ninth embodiment, the absolute value of the excitation angle in the second curve region |θ C2_prop The relationship between the thickness of the first electrode finger and the thickness of the second electrode finger is also set to Fig.33 The relationship shown is the same. Accordingly, in all the excitation parts in the first curve area and the second curve area, the resonant frequencies or anti-resonant frequencies are roughly consistent with each other. Moreover, as in the first embodiment, the unnecessary waves and transverse modes outside the passband can be dispersed, and the unnecessary waves and transverse modes outside the passband can be suppressed.

[0265] In addition, the relationship between the thickness of the first electrode finger and the second electrode finger and the frequency of each mode is different depending on the reverse velocity surface of the piezoelectric substrate. Therefore, depending on the structure of the piezoelectric substrate and the structure on the piezoelectric substrate, the absolute value of the excitation angle |θ C1_prop | and |θ C2_prop | When the thickness of each electrode finger is thicker, the resonant frequencies or anti-resonant frequencies of all the excitation parts may be roughly the same. As an example, an elastic wave device in which an IDT electrode provided on a substrate including only LiNbO3 that rotates Y-cut -4°X propagates is embedded in a thick SiO2 film can be cited. Alternatively, at the excitation angle θ passing through the reference line N C1_prop and the excitation angle θ C2_prop In the excitation portion at 0°, the thickness values ​​of the first electrode fingers and the second electrode fingers are not necessarily the maximum or the minimum.

[0266] In the first to ninth embodiments, the resonant frequencies or anti-resonant frequencies in all the excitation parts are made substantially consistent with each other by the structure of the IDT electrode. However, the resonant frequencies or anti-resonant frequencies in all the excitation parts may be made substantially consistent with each other by adjusting the thickness of the dielectric film covering the IDT electrode. This example is shown in the tenth embodiment and its modified example.

[0267] Fig.34 : is a schematic front cross-sectional view of the elastic wave device according to the tenth embodiment. Fig.34 is a schematic cross-sectional view along the reference line N.

[0268] The present embodiment differs from the first embodiment in that the duty ratio is fixed in the IDT electrode 98. The present embodiment also differs from the first embodiment in that a dielectric film 95 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 98. Except for the above aspects, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0269] The acoustic velocity of the transverse wave propagating through the dielectric film 95 of this embodiment is lower than the acoustic velocity of the main mode propagating through the dielectric film 95. The thickness of the dielectric film 95 is determined by the excitation angle θ of the excitation portion of the first curve region covered by the dielectric film 95. C1_prop Similarly, the thickness of the dielectric film 95 is determined according to the excitation angle θ of the excitation portion of the second curve region covered by the dielectric film 95. C2_prop But different.

[0270] Fig.35 is an absolute value of the excitation angle |θ in the excitation portion of the first curve region covered by the dielectric film in the tenth embodiment. C1_prop |A graph showing the relationship between and the thickness of the dielectric film.

[0271] like Fig.35 As shown, in this embodiment, the absolute value of the excitation angle of the excitation portion in the first curve region covered by the dielectric film 95 |θ C1_prop The larger |θ is, the thinner the dielectric film 95 is. In the tenth embodiment, the absolute value of the excitation angle in the second curve region |θ C2_prop | and the thickness of the dielectric film 95 are also set to Fig.35 The relationship shown is the same. Accordingly, in all the excitation parts in the first curve area and the second curve area, the resonant frequencies or anti-resonant frequencies are roughly consistent with each other. Moreover, as in the first embodiment, the unnecessary waves and transverse modes outside the passband can be dispersed, and the unnecessary waves and transverse modes outside the passband can be suppressed.

[0272] In the tenth embodiment, the acoustic velocity of the transverse wave propagating in the dielectric film 95 is lower than the acoustic velocity of the main mode propagating in the dielectric film 95. However, the relationship between the acoustic velocities of the waves propagating in the dielectric film is not limited to the above. The following is a modified example of the tenth embodiment in which only the acoustic velocity of the transverse wave propagating in the dielectric film is different from that of the tenth embodiment.

[0273] In a modification of the tenth embodiment, the acoustic velocity of the transverse wave propagating in the dielectric film is higher than the acoustic velocity of the main mode propagating in the dielectric film. In addition, in this modification, the absolute value of the excitation angle in the excitation portion of the first curve region covered by the dielectric film |θ C1_prop | and the thickness of the dielectric film are related as follows Fig.36 More specifically, the absolute value of the excitation angle in the excitation portion of the first curve region covered by the dielectric film |θ C1_prop The larger the value |θ is, the thicker the dielectric film is. In this variation, the absolute value of the excitation angle in the second curve region |θ C2_prop The relationship between | and the thickness of the dielectric film is also set to Fig.36 The relationship shown is the same. According to this, in all the excitation parts in the first curve region and the second curve region, the resonant frequencies or anti-resonant frequencies are substantially consistent with each other. In addition, as in the tenth embodiment, unnecessary waves and transverse modes outside the passband can be suppressed.

[0274] In addition, depending on the structure of the piezoelectric substrate and the like, the thickness of the portion of the dielectric film covering the excitation portion may not necessarily be the largest or smallest value at the portion through which the reference line N passes.

[0275] The elastic wave device according to the present invention can be used in, for example, a filter device. This example is shown below.

[0276] Fig.37 This is a circuit diagram of a filter device according to the eleventh embodiment.

[0277] The filter device 100 of this embodiment is a ladder filter. The filter device 100 has a first signal terminal 102 and a second signal terminal 103, and a plurality of series arm resonators and a plurality of parallel arm resonators. In the filter device 100, all series arm resonators and all parallel arm resonators are elastic wave resonators. Moreover, all series arm resonators and all parallel arm resonators are elastic wave devices according to the present invention. However, as long as at least one of the plurality of elastic wave resonators of the filter device 100 is an elastic wave device according to the present invention, it is sufficient.

[0278] The first signal terminal 102 is an antenna terminal. The antenna terminal is connected to an antenna. However, the first signal terminal 102 may not necessarily be an antenna terminal. For example, the first signal terminal 102 and the second signal terminal 103 may be configured as electrode pads or wiring.

[0279] Specifically, the plurality of series arm resonators of the present embodiment are a series arm resonator S1, a series arm resonator S2, and a series arm resonator S3. The plurality of series arm resonators are connected in series with each other between the first signal terminal 102 and the second signal terminal 103. Specifically, the plurality of parallel arm resonators are a parallel arm resonator P1 and a parallel arm resonator P2. The parallel arm resonator P1 is connected between the connection point between the series arm resonator S1 and the series arm resonator S2 and the ground potential. The parallel arm resonator P2 is connected between the connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential. In addition, the circuit structure of the filter device 100 is not limited to the above. For example, the filter device 100 may also include a longitudinally coupled resonator type elastic wave filter.

[0280] The elastic wave resonator in the filter device 100 is the elastic wave device according to the present invention. Therefore, the elastic wave resonator in the filter device 100 can suppress unnecessary waves in the transverse mode and outside the passband. Thus, unnecessary waves outside the passband of the filter device 100 can also be suppressed.

[0281] In addition, the curves in the shapes of the plurality of electrode fingers in the elastic wave device of each of the above-mentioned embodiments when viewed from above are smooth curves. In addition, the curves in the shapes of the plurality of electrode fingers when viewed from above may also be shapes formed by connecting straight lines of tiny sizes. The curves in the shapes of the plurality of electrode fingers when viewed from above may also be shapes formed by connecting a plurality of vertices to each other by curves. Alternatively, the curves in the shapes of the plurality of electrode fingers when viewed from above may not necessarily be smooth curves. This example is shown as the fifth variation of the first embodiment.

[0282] In by Fig.38 In the IDT electrode 8A in the fifth variant shown in an enlarged manner, the curve in the shape of each first electrode finger 16A when viewed from above is not a smooth curve. Specifically, the shape of each first electrode finger 16A when viewed from above is a shape formed by connecting straight lines. In addition, the straight lines in this shape are not straight lines of tiny size. More specifically, the length of the straight lines in this shape is, for example, a few % of the total length of the first electrode finger 16A. However, in this shape, the angle formed by the connected straight lines is, for example, as large as 160° or more and less than 180°. Therefore, the shape of each first electrode finger 16A when viewed from above is a shape that can be approximated by a curve.

[0283] The shape of each second electrode finger 17A in a plan view is also the same as the shape of each first electrode finger 16A in a plan view. In this modification, as in the first embodiment, unnecessary waves outside the passband and transverse modes can be suppressed.

[0284] Fig.39It is a schematic front cross-sectional view of an elastic wave device according to a twelfth embodiment.

[0285] The present embodiment is different from the first embodiment in that the IDT electrode 8 is buried in the protective film 119. Except for the above-described point, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0286] Specifically, the protective film 119 is provided on the piezoelectric layer 6 so as to cover the IDT electrode 8. The thickness of the protective film 119 is thicker than the thickness of the IDT electrode 8. The IDT electrode 8 is buried in the protective film 119. Thus, the IDT electrode 8 is less likely to be damaged.

[0287] The protective film 119 has a first protective layer 119a and a second protective layer 119b. The IDT electrode 8 is buried in the first protective layer 119a. The second protective layer 119b is provided on the first protective layer 119a. Accordingly, multiple effects can be obtained by the protective film 119. Specifically, in the present embodiment, silicon oxide is used as the material of the first protective layer 119a. Thus, the absolute value of the temperature coefficient of frequency (TCF) in the elastic wave device can be reduced. Therefore, the temperature characteristics of the elastic wave device can be improved. For the second protective layer 119b, silicon nitride is used. Thus, the moisture resistance of the elastic wave device can be improved.

[0288] Furthermore, in this embodiment, the IDT electrode 8 is also configured in the same manner as in the first embodiment. This makes it possible to suppress unnecessary waves and transverse modes outside the passband.

[0289] However, the materials of the first protective layer 119a and the second protective layer 119b are not limited to the above. The protective film 119 may be a single layer or a laminate of three or more layers.

[0290] Fig.40 It is a schematic front cross-sectional view of an elastic wave device according to a thirteenth embodiment.

[0291] The present embodiment is different from the first embodiment in that IDT electrodes 8 are provided on both principal surfaces of the piezoelectric layer 6. Except for the above point, the elastic wave device of the present embodiment has the same structure as the elastic wave device 1 of the first embodiment.

[0292] The piezoelectric layer 6 has a first principal surface 6a and a second principal surface 6b. The first principal surface 6a and the second principal surface 6b are opposite to each other. It is pointed out in advance that the piezoelectric layer 6 in each of the above-mentioned embodiments also has a first principal surface 6a and a second principal surface 6b. Moreover, in each of the above-mentioned embodiments and the present embodiment, an IDT electrode is provided on the first principal surface 6a. In the present embodiment, an IDT electrode 8 is also provided on the second principal surface 6b. The IDT electrode 8 provided on the second principal surface 6b is buried in the second layer 5b in the intermediate layer 5.

[0293] The IDT electrode 8 provided on the first principal surface 6a of the piezoelectric layer 6 and the IDT electrode 8 provided on the second principal surface 6b are opposed to each other with the piezoelectric layer 6 interposed therebetween. In the elastic wave device of this embodiment, the IDT electrode 8 on the first principal surface 6a is configured in the same manner as in the first embodiment. This can suppress unnecessary waves and transverse modes outside the passband.

[0294] In addition, the IDT electrodes 8 provided on the first principal surface 6 a and the second principal surface 6 b of the piezoelectric layer 6 may have different design parameters, for example.

[0295] The following describes the first to third variations of the 13th embodiment, in which only the structure of the electrode provided on the second main surface of the piezoelectric layer and at least one of the stacked structures of the piezoelectric substrate are different from the 13th embodiment. In these first to third variations, as in the 13th embodiment, it is possible to suppress unnecessary waves and transverse modes outside the passband.

[0296] exist Fig.41 In the first variation shown, the layer structure of the piezoelectric substrate 122 is different from that of the thirteenth embodiment. Specifically, the piezoelectric substrate 122 has a supporting substrate 4, a dielectric layer 125, and a piezoelectric layer 6. The dielectric layer 125 is provided on the supporting substrate 4. The piezoelectric layer 6 is provided on the dielectric layer 125. In this variation, the dielectric layer 125 has a frame shape. That is, the dielectric layer 125 has a through hole.

[0297] The support substrate 4 blocks one side of the through hole of the dielectric layer 125. The piezoelectric layer 6 blocks the other side of the through hole of the dielectric layer 125. Thus, a hollow portion 122c is formed in the piezoelectric substrate 122. A portion of the piezoelectric layer 6 and a portion of the support substrate 4 are opposed to each other with the hollow portion 122c sandwiched therebetween. The IDT electrode 8 provided on the second main surface 6b of the piezoelectric layer 6 is located in the hollow portion 122c.

[0298] exist Fig.42 In the second modification shown, a plate-shaped electrode 128 is provided on the second main surface 6b of the piezoelectric layer 6. The IDT electrode 8 and the electrode 128 face each other with the piezoelectric layer 6 interposed therebetween.

[0299] exist Fig.43 In the third modification shown, the piezoelectric substrate 122 is configured similarly to the first modification, and an electrode 128 similar to the second modification is provided on the second principal surface 6b of the piezoelectric layer 6. The electrode 128 is located in the hollow portion 122c.

[0300] In the 12th embodiment, the 13th embodiment and each modified example, an example is shown in which the IDT electrode 8 has the same structure as the first embodiment. However, when the structure of the IDT electrode is set to the structure of the present invention other than the first embodiment, the structures of the 12th embodiment, the 13th embodiment and each modified example can also be adopted.

[0301] Examples of aspects of the elastic wave device and the filter device according to the present invention are summarized and described below.

[0302] <1> An elastic wave device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode disposed on the piezoelectric layer, wherein the IDT electrode comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other, an imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as a first envelope, and an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as a second envelope, wherein The area between the first envelope and the second envelope in the IDT electrode is an intersection area, and the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a top view respectively include at least two curved portions in the intersection area in which the first electrode fingers and the second electrode fingers are bent in different directions. In the intersection area, the closer to the first envelope or the second envelope, the more the value of at least any one of the duty cycle, the electrode finger pitch, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

[0303] <2> exist <1> In the elastic wave device described, the at least two curved portions in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers when viewed from above respectively include shapes of circular arcs or elliptical arcs, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers when viewed from above respectively have at least one inflection point, and the intersection area includes at least two curved areas in which the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers when viewed from above are respectively shapes of single circular arcs or elliptical arcs.

[0304] <3> exist <2> In the elastic wave device described, when the center of the circle of the arc in the shape of the first electrode finger and the second electrode finger in each of the curved regions or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and the portion on any straight line passing through the fixed point in each of the curved regions is set as an excitation portion, in the intersection region, the value of at least any one of the duty cycle, the electrode finger pitch, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of an increasing direction and a decreasing direction as the excitation portion is closer to the first envelope or the second envelope.

[0305] <4> An elastic wave device comprises: a piezoelectric substrate including a piezoelectric layer; and an IDT electrode disposed on the piezoelectric layer, the IDT electrode comprising a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, the plurality of first electrode fingers and the plurality of second electrode fingers being interlaced with each other, an imaginary line formed by connecting the top ends of the plurality of second electrode fingers being set as a first envelope, and an imaginary line formed by connecting the top ends of the plurality of first electrode fingers being set as a second envelope, a region between the first envelope and the second envelope in the IDT electrode being a cross region, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view respectively comprising the shapes of at least two circular arcs or elliptical arcs, and having at least one inflection point, the cross region comprising the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view respectively being a single circular arc or elliptical arc, At least two curved regions in the shape of an elliptical arc, the intersection region has a first edge region including the first envelope, a second edge region including the second envelope, and a central region sandwiched by the first edge region and the second edge region, at least one of the first edge region and the second edge region constitutes a low sound speed region whose sound speed is lower than that in the central region, and when the center of the circle of the arc in the shape including the first electrode finger and the second electrode finger in each of the curved regions or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and a portion of an arbitrary straight line passing through the fixed point in the region of each of the curved regions located in the central region is set as an excitation portion, the closer the excitation portion is to the first envelope or the second envelope, the more the value of at least any one of the duty cycle, the electrode finger pitch, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

[0306] <5> exist <4> In the elastic wave device described above, in the first edge region, the plurality of first electrode fingers and the plurality of second electrode fingers have a wide portion having a width wider than that in the central region, thereby forming the low acoustic velocity region.

[0307] <6> exist <4> or <5> The elastic wave device described above further includes a mass addition film provided in the first edge region, and the mass addition film, the plurality of first electrode fingers, and the plurality of second electrode fingers are stacked to form the low acoustic velocity region.

[0308] <7> exist <4> to <6> In the elastic wave device described in any one of the items, the elastic wave device also has a high acoustic velocity membrane arranged in the central area. By providing the high acoustic velocity membrane, the sound speed in the central area becomes higher than the sound speed in the first edge area and the second edge area, thereby forming the low acoustic velocity area in the first edge area and the second edge area.

[0309] <8> exist <3> to <7> In the elastic wave device described in any one of the items, the extension lines of the boundary lines between the different curved areas pass through the fixed point, and when the straight line including the boundary line and the extension line of the boundary line is set as the baseline, the angle formed by the straight line passing through the fixed point and the excitation part and the baseline is defined, and the excitation angle formed by the excitation direction of the elastic wave at the intersection of the straight line passing through the fixed point and the excitation part and the first electrode finger or the second electrode finger and the baseline is defined, at least any one of the duty cycle, the electrode finger spacing and the thickness of the multiple first electrode fingers and the multiple second electrode fingers changes according to the angle or the excitation angle, so that the resonant frequencies or anti-resonant frequencies in all the excitation parts are substantially consistent with each other.

[0310] <9> exist <3> to <7> In the elastic wave device described in any one of the items, one of the multiple curved areas includes the first envelope, and the extension of the first envelope passes through the fixed point of the curved area. When a straight line including the first envelope and the extension of the first envelope is set as a baseline, an angle formed by a straight line passing through the fixed point of the curved area including the first envelope and the excitation part in the curved area and the baseline is defined, and an excitation angle formed by an excitation direction of the elastic wave at an intersection of a straight line passing through the fixed point and the excitation part and the first electrode finger or the second electrode finger and the baseline is defined, at least any one of a duty cycle, an electrode finger pitch, and a thickness of the multiple first electrode fingers and the multiple second electrode fingers is changed according to each of the angles and the excitation angle, so that the resonant frequencies or anti-resonant frequencies in all the excitation parts of the curved area are substantially consistent with each other.

[0311] <10> exist <8> or <9> In the elastic wave device described above, a piezoelectric single crystal is used as a material of the piezoelectric layer, the piezoelectric layer has a propagation axis, and the propagation axis and the reference line extend in parallel.

[0312] <11> exist <8> to <10> In the elastic wave device described in any one of the above, the electrode finger pitch becomes narrower as the absolute value of the angle or the excitation angle becomes larger.

[0313] <12> exist <8> to <10> In the elastic wave device described in any one of the above, the electrode finger pitch increases as the absolute value of the angle or the excitation angle increases.

[0314] <13> exist <8> to <12> In the elastic wave device described in any one of the above, the thicknesses of the first electrode fingers and the second electrode fingers become thinner as the absolute values ​​of the angle and the excitation angle become larger.

[0315] <14> exist <8> to <12> In the elastic wave device described in any one of the above, the thicknesses of the first electrode fingers and the second electrode fingers increase as the absolute values ​​of the angle and the excitation angle increase.

[0316] <15> exist <8> to <14> In the elastic wave device described in any one of the above, a dielectric film is further provided on the piezoelectric layer, and the dielectric film is provided to cover the IDT electrode.

[0317] The larger the angle or the absolute value of the excitation angle is, the thinner the dielectric film is.

[0318] <16> exist <8> to <14> In the elastic wave device described in any one of the above, a dielectric film is further provided on the piezoelectric layer, the dielectric film is provided to cover the IDT electrode, and the thickness of the dielectric film increases as the absolute value of the angle or the excitation angle increases.

[0319] <17> exist <8> to <16> In the elastic wave device described in any one of the above, the duty ratio decreases as the absolute values ​​of the angle and the excitation angle increase.

[0320] <18> exist <8> to <16> In the elastic wave device described in any one of the above, the duty ratio increases as the absolute values ​​of the angle and the excitation angle increase.

[0321] <19> exist <17> In the elastic wave device described, the elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes, the plurality of first offset electrodes are respectively connected to the first bus bar, the plurality of second offset electrodes are respectively connected to the second bus bar, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, the top ends of the first electrode fingers and the top ends of the second offset electrodes are opposed to each other with a gap therebetween, the shapes of the plurality of first offset electrodes include a circular arc included in a circle centered at the fixed point, or a shape of an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci, and in a region between the first bus bar and the intersection region, the closer to the first bus bar, the smaller the duty ratio becomes.

[0322] <20> exist <18> In the elastic wave device described, the elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes, the plurality of first offset electrodes are respectively connected to the first bus bar, the plurality of second offset electrodes are respectively connected to the second bus bar, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, the top ends of the first electrode fingers and the top ends of the second offset electrodes are opposed to each other with a gap therebetween, the shapes of the plurality of first offset electrodes include a circular arc included in a circle centered at the fixed point, or a shape of an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci, and in a region between the first bus bar and the intersection region, the closer to the first bus bar, the larger the duty ratio becomes.

[0323] <21> exist <3> to <18> In the elastic wave device described in any one of the items, the elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes, the plurality of first offset electrodes are respectively connected to the first bus bar, the plurality of second offset electrodes are respectively connected to the second bus bar, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, the top ends of the first electrode fingers and the top ends of the second offset electrodes are opposed to each other with a gap therebetween, the shape of the plurality of first offset electrodes includes a circular arc included in a circle centered at the fixed point, or a shape of an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci, and the duty ratio is constant in a region between the first bus bar and the intersection region.

[0324] <22> In the claim <3> to <18> In the elastic wave device described in any one of the items, the elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes, the plurality of first offset electrodes are respectively connected to the first bus bar, the plurality of second offset electrodes are respectively connected to the second bus bar, the top ends of the second electrode fingers and the top ends of the first offset electrodes are opposed to each other with a gap therebetween, the top ends of the first electrode fingers and the top ends of the second offset electrodes are opposed to each other with a gap therebetween, and the first offset electrodes have a linear shape.

[0325] <23> exist <3> to <22> In the elastic wave device described in any one of the items, when α2 / α1 is set as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, the shapes of the first electrode fingers and the second electrode fingers in a plan view include a portion where α2 / α1>1.

[0326] <24> exist <3> to <22> In the elastic wave device described in any one of the items, when α2 / α1 is set as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, the shapes of the first electrode fingers and the second electrode fingers in a plan view include a portion where α2 / α1<1.

[0327] <25> exist <3> to <22> In the elastic wave device described in any one of the items, when α2 / α1 is set as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, the shapes of the first electrode fingers and the second electrode fingers in a plan view include a portion where α2 / α1=1.

[0328] <26> exist <1> to <25> In the elastic wave device described in any one of the above, the shapes of the first electrode fingers and the second electrode fingers in a plan view include straight line shapes.

[0329] <27> exist <1> to <26> In the elastic wave device described in any one of the above, the piezoelectric substrate includes a supporting substrate, and the piezoelectric layer is provided on the supporting substrate.

[0330] <28> exist <27> In the elastic wave device described above, the piezoelectric substrate includes an intermediate layer provided between the supporting substrate and the piezoelectric layer.

[0331] <29> exist <1> to <26> In the elastic wave device described in any one of the above, the piezoelectric substrate includes only the piezoelectric layer.

[0332] <30> A filter device comprises a plurality of elastic wave resonators, at least one of which is <1> to <29> An elastic wave device as described in any one of the items.

[0333] Description of Reference Numerals

[0334] 1…Elastic wave device

[0335] 2, 2A, 2B…Piezoelectric substrate

[0336] 3…Supporting member

[0337] 4. 4B…Supporting base plate

[0338] 4c…concave part

[0339] 5.5A…Middle layer

[0340] 5a, 5b…1st floor, 2nd floor

[0341] 6…Piezoelectric layer

[0342] 6a, 6b…1st main surface, 2nd main surface

[0343] 7… Acoustic reflective membrane

[0344] 8, 8A…IDT electrode

[0345] 9A, 9B…Reflector

[0346] 9a, 9b…Electrode fingers

[0347] 12a, 12b…low acoustic impedance layer

[0348] 13a~13c…High acoustic impedance layer

[0349] 14, 15…1st bus bar, 2nd bus bar

[0350] 16, 17…1st electrode finger, 2nd electrode finger

[0351] 16A, 16A...1st electrode finger, 2nd electrode finger

[0352] 18, 19 ... first offset electrode, second offset electrode

[0353] 28…IDT electrode

[0354] 36A, 36B ... first electrode finger

[0355] 37A, 37B...second electrode finger

[0356] 38, 38A, 38B ... first offset electrode

[0357] 48…IDT electrode

[0358] 52…High sound velocity membrane

[0359] 56, 57…1st electrode finger, 2nd electrode finger

[0360] 56b, 57a…wide portion

[0361] 58, 58A…IDT electrode

[0362] 59A, 59B…Quality additional film

[0363] 68, 78, 88…IDT electrode

[0364] 95…Dielectric film

[0365] 98…IDT electrode

[0366] 100...Filter device

[0367] 102, 103 ... 1st signal terminal, 2nd signal terminal

[0368] 119…Protective film

[0369] 119a, 119b ... first protective layer, second protective layer

[0370] 122…Piezoelectric substrate

[0371] 122c…Hollow part

[0372] 125…Dielectric layer

[0373] 128…Electrode

[0374] 208…IDT electrode

[0375] 209A, 209B…Reflector

[0376] 218…IDT electrode

[0377] C1, C2…fixed point

[0378] D…Crossover area

[0379] E1, E2…1st envelope, 2nd envelope

[0380] F…Central area

[0381] g1, g2…gap

[0382] G1, G2...1st gap area, 2nd gap area

[0383] H1, H2…1st edge area, 2nd edge area

[0384] N, N1, N2…baseline

[0385] O…Borderline

[0386] P1, P2…Parallel arm resonator

[0387] S1~S3…Series arm resonator

[0388] T…Straight line area

[0389] W1~W4...1st curve area to 4th curve area.

Claims

1. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer; and IDT electrode, disposed on the piezoelectric layer, The IDT electrode comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other. An imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as a first envelope, an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as a second envelope, and a region between the first envelope and the second envelope in the IDT electrode is a crossing region, The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view include at least two curved portions in the intersection region, in which the first electrode fingers and the second electrode fingers are bent in different directions. In the intersection area, the closer to the first envelope or the second envelope, the value of at least any one of the duty cycle, the electrode finger pitch, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

2. The elastic wave device according to claim 1, wherein: The at least two curved portions in the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers when viewed from above respectively include shapes of circular arcs or elliptical arcs, the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers when viewed from above respectively have at least one inflection point, and the intersection area includes at least two curved areas in which the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers when viewed from above are respectively shapes of single circular arcs or elliptical arcs.

3. The elastic wave device according to claim 2, wherein: When the center of the circle of the arc in the shape of the first electrode finger and the second electrode finger in each of the curved regions or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and the portion on any straight line passing through the fixed point in each of the curved regions is set as an excitation portion, in the intersection region, the closer the excitation portion is to the first envelope or the second envelope, the more the value of at least any one of the duty cycle, the electrode finger spacing, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of a direction of increasing and a direction of decreasing.

4. An elastic wave device comprising: A piezoelectric substrate including a piezoelectric layer; and IDT electrode, disposed on the piezoelectric layer, The IDT electrode comprises a first bus bar and a second bus bar facing each other, a plurality of first electrode fingers connected to the first bus bar at one end, and a plurality of second electrode fingers connected to the second bus bar at one end, wherein the plurality of first electrode fingers and the plurality of second electrode fingers are interlaced with each other. An imaginary line formed by connecting the top ends of the plurality of second electrode fingers is set as a first envelope, an imaginary line formed by connecting the top ends of the plurality of first electrode fingers is set as a second envelope, and a region between the first envelope and the second envelope in the IDT electrode is a crossing region, The shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view respectively include at least two circular arc shapes or elliptical arc shapes and have at least one inflection point, and the intersection region includes at least two curved regions in which the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view are respectively single circular arc shapes or elliptical arc shapes, The intersection region includes a first edge region including the first envelope, a second edge region including the second envelope, and a central region sandwiched by the first edge region and the second edge region, and at least one of the first edge region and the second edge region constitutes a low sound velocity region having a sound velocity lower than that in the central region. When the center of the circle of the arc in the shape of the first electrode finger and the second electrode finger in each of the curved areas or the midpoint of the two foci of the ellipse including the elliptical arc is set as a fixed point, and the portion of any straight line passing through the fixed point in the area of ​​the central area of ​​each of the curved areas is set as an excitation portion, the value of at least any one of the duty cycle, the electrode finger spacing, and the thickness of the plurality of first electrode fingers and the plurality of second electrode fingers changes in one of an increasing direction and a decreasing direction as the excitation portion is closer to the first envelope or the second envelope.

5. The elastic wave device according to claim 4, wherein: In the first edge region, the plurality of first electrode fingers and the plurality of second electrode fingers have wide portions having widths wider than those in the central region, thereby forming the low acoustic velocity region.

6. The elastic wave device according to claim 4 or 5, wherein: The elastic wave device further includes a mass addition film provided in the first edge region. The mass addition film, the plurality of first electrode fingers, and the plurality of second electrode fingers are stacked to form the low acoustic velocity region.

7. The elastic wave device according to any one of claims 4 to 6, wherein: The elastic wave device further includes a high acoustic velocity membrane provided in the central region. By providing the acoustic velocity increasing film, the acoustic velocity in the central region becomes higher than the acoustic velocity in the first edge region and the second edge region, so that the low acoustic velocity region is formed in the first edge region and the second edge region.

8. The elastic wave device according to any one of claims 3 to 7, wherein: The extension lines of the boundary lines of the different curved areas pass through the fixed point. When a straight line including the boundary line and an extension of the boundary line is set as a baseline, an angle formed by a straight line passing through the fixed point and the excitation portion and the baseline is defined, and an excitation angle formed by an excitation direction of an elastic wave at an intersection of a straight line passing through the fixed point and the excitation portion and the first electrode finger or the second electrode finger and the baseline is defined, at least any one of a duty cycle, an electrode finger spacing, and a thickness of the plurality of first electrode fingers and the plurality of second electrode fingers is changed according to the angle or the excitation angle, so that the resonant frequencies or anti-resonant frequencies in all the excitation portions are substantially consistent with each other.

9. The elastic wave device according to any one of claims 3 to 7, wherein: One of the plurality of curve regions includes the first envelope, and an extension line of the first envelope passes through the fixed point of the curve region. When a straight line including the first envelope and an extension of the first envelope is set as a baseline, an angle formed by a straight line passing through the fixed point of the curve area including the first envelope and the excitation part in the curve area and the baseline is defined, and an excitation angle formed by an excitation direction of an elastic wave at an intersection of a straight line passing through the fixed point and the excitation part and the first electrode finger or the second electrode finger and the baseline is defined, at least any one of a duty cycle, an electrode finger pitch, and a thickness of the plurality of first electrode fingers and the plurality of second electrode fingers is changed according to each of the angles and the excitation angle, so that the resonant frequencies or anti-resonant frequencies in all the excitation parts of the curve area are substantially consistent with each other.

10. The elastic wave device according to claim 8 or 9, wherein: As the material of the piezoelectric layer, a piezoelectric single crystal is used. The piezoelectric layer has a propagation axis, and the propagation axis and the reference line extend in parallel.

11. The elastic wave device according to any one of claims 8 to 10, wherein: The larger the angle or the absolute value of the excitation angle is, the narrower the electrode finger pitch is.

12. The elastic wave device according to any one of claims 8 to 10, wherein: The larger the absolute value of the angle and the excitation angle is, the wider the electrode finger pitch is.

13. The elastic wave device according to any one of claims 8 to 12, wherein: The greater the absolute values ​​of the angle and the excitation angle are, the thinner the thicknesses of the first electrode fingers and the second electrode fingers are.

14. The elastic wave device according to any one of claims 8 to 12, wherein: The greater the absolute values ​​of the angle and the excitation angle are, the thicker the first electrode fingers and the second electrode fingers are.

15. The elastic wave device according to any one of claims 8 to 14, wherein: A dielectric film is further provided on the piezoelectric layer, wherein the dielectric film is provided to cover the IDT electrode. The larger the absolute value of the angle and the excitation angle is, the thinner the thickness of the dielectric film is.

16. The elastic wave device according to any one of claims 8 to 14, wherein: A dielectric film is further provided on the piezoelectric layer, wherein the dielectric film is provided to cover the IDT electrode. The larger the absolute value of the angle and the excitation angle is, the thicker the dielectric film is.

17. The elastic wave device according to any one of claims 8 to 16, wherein: The larger the absolute value of the angle and the excitation angle is, the smaller the duty cycle is.

18. The elastic wave device according to any one of claims 8 to 16, wherein: The larger the angle or the absolute value of the excitation angle is, the larger the duty cycle is.

19. The elastic wave device according to claim 17, wherein: The elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes. The plurality of first offset electrodes are connected to the first bus bar, respectively, and the plurality of second offset electrodes are connected to the second bus bar, respectively. The tip of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The shapes of the plurality of first offset electrodes include a circular arc included in a circle with the fixed point as the center, or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci. In a region between the first bus bar and the intersection region, the duty ratio becomes smaller as it is closer to the first bus bar.

20. The elastic wave device according to claim 18, wherein The elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes. The plurality of first offset electrodes are connected to the first bus bar, respectively, and the plurality of second offset electrodes are connected to the second bus bar, respectively. The tip of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The shapes of the plurality of first offset electrodes include a circular arc included in a circle with the fixed point as the center, or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci. In a region between the first bus bar and the intersection region, the duty ratio increases as the region is closer to the first bus bar.

21. The elastic wave device according to any one of claims 3 to 18, wherein: The elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes. The plurality of first offset electrodes are connected to the first bus bar, respectively, and the plurality of second offset electrodes are connected to the second bus bar, respectively. The tip of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The shapes of the plurality of first offset electrodes include a circular arc included in a circle with the fixed point as the center, or an elliptical arc included in an ellipse with the fixed point as the midpoint of two foci. In the region between the first bus bar and the intersection region, the duty ratio is constant.

22. The elastic wave device according to any one of claims 3 to 18, wherein: The elastic wave device includes a plurality of first offset electrodes and a plurality of second offset electrodes. The plurality of first offset electrodes are connected to the first bus bar, respectively, and the plurality of second offset electrodes are connected to the second bus bar, respectively. The tip of the second electrode finger and the tip of the first offset electrode are opposed to each other with a gap therebetween, and the tip of the first electrode finger and the tip of the second offset electrode are opposed to each other with a gap therebetween. The first offset electrode has a linear shape.

23. The elastic wave device according to any one of claims 3 to 22, wherein: When α2 / α1 is defined as an ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, the shapes of the first electrode fingers and the second electrode fingers in a plan view include a portion where α2 / α1>1.

24. The elastic wave device according to any one of claims 3 to 22, wherein: When α2 / α1 is defined as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, the shapes of the first electrode fingers and the second electrode fingers in a plan view include a portion where α2 / α1<1.

25. The elastic wave device according to any one of claims 3 to 22, wherein: When α2 / α1 is defined as the ellipticity coefficient of the shapes of the plurality of first electrode fingers and the plurality of second electrode fingers in a plan view, the shapes of the first electrode fingers and the second electrode fingers in a plan view include a portion where α2 / α1=1.

26. The elastic wave device according to any one of claims 1 to 25, wherein: The shapes of the first electrode fingers and the second electrode fingers in a plan view include straight line shapes.

27. The elastic wave device according to any one of claims 1 to 26, wherein: The piezoelectric substrate has a supporting substrate. The piezoelectric layer is provided on the supporting substrate.

28. The elastic wave device according to claim 27, wherein: The piezoelectric substrate includes an intermediate layer provided between the supporting substrate and the piezoelectric layer.

29. The elastic wave device according to any one of claims 1 to 26, wherein: The piezoelectric substrate includes only the piezoelectric layer.

30. A filter device comprising a plurality of elastic wave resonators, At least one of the elastic wave resonators is the elastic wave device according to any one of claims 1 to 29.

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