Elastic wave element, elastic wave filter device, and multiplexer

Abstract

To suppress the generation of a ripple on a frequency side that is higher than an antiresonance frequency of an elastic wave element.SOLUTION: An elastic wave element 10 comprises: a first IDT electrode 11 formed onto a first main surface 100a of a piezoelectric layer 100 and a plurality of first reflectors 31; and a second IDT electrode 22 formed onto a second main surface 100b of the piezoelectric layer 100 and a plurality of second reflectors 42. In the case where a region between the plurality of first reflectors 31 in a first direction d1 is a first region m1, a region between the plurality of second reflectors 42 in the first direction d1 is a second region m2, and the minimum region containing the first region m1 and the second region m2 in view from a third direction d3 vertical to both of the first direction d1 and a second direction d2 is an inter-reflector region MR, first electrode fingers 11a and 11b of the first IDT electrode 11 and second electrode fingers 22a and 22b of the second IDT electrode 22 in an end part region E of the first direction d1 of the inter-reflector region MR include a region where they do not face each other with respect to the third direction d3.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an acoustic wave element, an acoustic wave filter device, and a multiplexer. [Background technology]

[0002] In recent years, multi-band systems have been used to improve the data transmission speed of mobile phones. In such cases, since transmission and reception of signals in multiple frequency bands may be performed, multiple filter devices that pass high-frequency signals in different frequency bands are arranged in the front-end circuit of the mobile phone. In this case, the multiple filter devices are required to have high isolation from adjacent bands.

[0003] Patent Document 1 discloses a piezoelectric vibrator in which an acoustic wave is confined in a part of a piezoelectric structure. In Fig. 9 of Patent Document 1, as an example of a piezoelectric vibrator, an acoustic wave element including a piezoelectric layer, an IDT electrode and a reflector formed on a front surface of the piezoelectric layer, and an IDT electrode and a reflector formed on a back surface of the piezoelectric layer is disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2025-217818 A Summary of the Invention [Problem to be solved by the invention]

[0005] The acoustic wave element described in Patent Document 1 has a problem in that ripples occur at frequencies higher than the anti-resonance frequency of the acoustic wave element.

[0006] The present invention has been made to solve the above-mentioned problems, and has an object to provide an acoustic wave element etc. that can suppress the occurrence of ripples on the higher frequency side than the anti-resonance frequency. [Means for solving the problem]

[0007] In order to achieve the above object, an acoustic wave element according to one aspect of the present invention includes a piezoelectric layer, a first IDT electrode and a plurality of first reflectors formed on a first main surface of the piezoelectric layer, and a second IDT electrode and a plurality of second reflectors formed on a second main surface facing the first main surface of the piezoelectric layer, wherein the first IDT electrode has a plurality of first electrode fingers arranged to extend in a second direction intersecting with a first direction in a direction along the first main surface, and each of the plurality of first reflectors has a plurality of first reflecting electrode fingers arranged on both outsides of the first IDT electrode in the first direction and arranged to extend in the second direction, the second IDT electrode has a plurality of second electrode fingers arranged to extend in the second direction intersecting with the first direction in a direction along the second main surface, and the plurality of second reflectors each of the reflectors has a plurality of second reflective electrode fingers arranged on both outer sides of the second IDT electrode in the first direction and extending in the second direction, where when a region between the plurality of first reflectors in the first direction is defined as a first region, a region between the plurality of second reflectors in the first direction is defined as a second region, and a smallest region including the first region and the second region as viewed from a third direction perpendicular to both the first direction and the second direction is defined as an inter-reflector region, the inter-reflector region has a region in an end region in the first direction where the first electrode fingers and the second electrode fingers do not face each other in the third direction, or the inter-reflector region has a region in an end region in the first direction where the first reflective electrode fingers and the second reflective electrode fingers do not face each other in the third direction.

[0008] In order to achieve the above object, an acoustic wave filter device according to one aspect of the present invention includes the above acoustic wave element.

[0009] In order to achieve the above-mentioned object, a multiplexer according to one embodiment of the present invention includes a plurality of filters including the above-mentioned acoustic wave filter device, wherein an input / output terminal and one of the input / output terminals of each of the plurality of filters are directly or indirectly connected to a common terminal, and at least one of the plurality of filters excluding the acoustic wave filter device has a passband higher in frequency than the passband of the acoustic wave filter device. Effect of the Invention

[0010] The acoustic wave element and the like according to the present invention can suppress the occurrence of ripples on the higher frequency side than the anti-resonance frequency. [Brief description of the drawings]

[0011] [Figure 1A] 2 is a top view of a first IDT electrode and a first reflector of the acoustic wave element in accordance with the first embodiment. FIG. [Figure 1B] 4 is a top view of a second IDT electrode and a second reflector of the acoustic wave element in accordance with the first embodiment. FIG. [Diagram 2] 2 is a cross-sectional view of the acoustic wave element shown in FIG. 1A and FIG. 1B taken along line II-II. [Diagram 3] 3 is a cross-sectional view of the acoustic wave element taken along line III-III shown in FIGS. 1A and 1B. [Figure 4A] 11 is a top view of a first IDT electrode and a first reflector of an acoustic wave element of a comparative example. FIG. [Figure 4B] 13 is a top view of a second IDT electrode and a second reflector of the acoustic wave element of the comparative example. FIG. [Diagram 5] 4C is a cross-sectional view of the acoustic wave element taken along line VV shown in FIGS. 4A and 4B. [Figure 6A] 1 is a graph showing phase characteristics of acoustic wave devices according to Examples 1, 2, 3, and 4, and a comparative example. [Figure 6B] FIG. 6B is an enlarged view of a portion VIB in FIG. 6A. [Figure 6C] FIG. 6B is an enlarged view of the VIC portion in FIG. 6A. [Figure 7A]1 is a top view of a first IDT electrode and a first reflector of an acoustic wave element in accordance with a first modification of the first embodiment. FIG. [Figure 7B] 13 is a top view of a second IDT electrode and a second reflector of an acoustic wave element in accordance with a first modification of the first embodiment. FIG. [Figure 8] 8 is a cross-sectional view of the acoustic wave element shown in FIGS. 7A and 7B taken along line VIII-VIII. FIG. [Figure 9A] 11 is a top view of a first IDT electrode and a first reflector of an acoustic wave element in accordance with a second modification of the first embodiment. FIG. [Figure 9B] 11 is a top view of a second IDT electrode and a second reflector of an acoustic wave element in accordance with a second modification of the first embodiment. FIG. [Figure 10] 9C is a cross-sectional view of the acoustic wave element shown in FIGS. 9A and 9B taken along line XX. FIG. [Figure 11A] 13 is a top view of a first IDT electrode and a first reflector of an acoustic wave element in accordance with a third modification of the first embodiment. FIG. [Figure 11B] 13 is a top view of a second IDT electrode and a second reflector of an acoustic wave element in accordance with a third modification of the first embodiment. FIG. [Figure 12] 12 is a cross-sectional view of the acoustic wave element taken along line XII-XII shown in FIGS. 11A and 11B. [Figure 13A] 13 is a top view of a first IDT electrode and a first reflector of an acoustic wave element in accordance with a fourth modification of the first embodiment. FIG. [Figure 13B] 13 is a top view of a second IDT electrode and a second reflector of an acoustic wave element in accordance with a fourth modification of the first embodiment. FIG. [Figure 14] 14 is a cross-sectional view of the acoustic wave element shown in FIGS. 13A and 13B taken along line XIV-XIV. FIG. [Figure 15A] 13 is a top view of a first IDT electrode and a first reflector of an acoustic wave element in accordance with a fifth modification of the first embodiment. FIG. [Figure 15B] 13 is a top view of a second IDT electrode and a second reflector of an acoustic wave element in accordance with a fifth modification of the first embodiment. FIG. [Figure 16]16 is a cross-sectional view of the acoustic wave element shown in FIGS. 15A and 15B taken along line XVI-XVI. FIG. [Figure 17] 1 is a diagram illustrating a circuit configuration of an acoustic wave filter device according to a second embodiment. [Figure 18] FIG. 11 is a circuit configuration diagram of a multiplexer and its peripheral circuits according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the present invention will be described in detail with reference to figures and tables. Note that the examples described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following examples are merely examples and are not intended to limit the present invention. Among the components in the following examples, components that are not described in the independent claims are described as optional components. Also, the size or size ratio of the components shown in the drawings is not necessarily strict.

[0013] (Embodiment 1) [Structure of acoustic wave element] The structure of the acoustic wave device according to the first embodiment will be described with reference to FIGS. 1A to 3. FIG.

[0014] Fig. 1A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 10 in accordance with embodiment 1. Fig. 1B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 10. Fig. 2 is a cross-sectional view of acoustic wave element 10 taken along line II-II shown in Figs. 1A and 1B.

[0015] Acoustic wave element 10 shown in FIGS. 1A, 1B, and 2 is a one-port surface acoustic wave (SAW) resonator including a piezoelectric layer 100, a plurality of IDT (InterDigital Transducer) electrodes, and a plurality of reflectors.

[0016] The piezoelectric layer 100 shown in FIG. 2 is, for example, a θ° Y-cut X-propagation LiNbO 3 It is made of a piezoelectric single crystal or piezoelectric ceramics (a lithium niobate single crystal or ceramics cut along a plane whose normal is an axis rotated θ degrees from the Y axis in the Z axis direction around the X axis, and in which surface acoustic waves propagate in the X axis direction).

[0017] The piezoelectric layer 100 has a first main surface 100a on one side and a second main surface 100b on the other side. The first main surface 100a and the second main surface 100b, which are both main surfaces of the piezoelectric layer 100, face back to back to each other. The thickness of the piezoelectric layer 100 is determined by the IDT wavelength (λ IDT ) The dimensions are as follows:

[0018] The multiple IDT electrodes are composed of a first IDT electrode 11 and a second IDT electrode 22. The first IDT electrode 11 is formed on a first main surface 100a of the piezoelectric layer 100, and the second IDT electrode 22 is formed on a second main surface 100b of the piezoelectric layer 100. In other words, an IDT electrode is formed on each of the two main surfaces of the piezoelectric layer 100.

[0019] The multiple reflectors are composed of multiple first reflectors 31 and multiple second reflectors 42. The multiple first reflectors 31 are formed on a first main surface 100a of the piezoelectric layer 100, and the multiple second reflectors 42 are formed on a second main surface 100b of the piezoelectric layer 100. In this example, two reflectors are formed on each of the two main surfaces of the piezoelectric layer 100.

[0020] 1A and 1B each show a perspective view of the IDT electrode and the reflector viewed from a direction perpendicular to the main surface of the piezoelectric layer 100. As shown in Fig. 1A, the electrodes of the first reflector 31 are disposed on both outer sides of the first IDT electrode 11 in a first direction d1, which is the acoustic wave propagation direction. As shown in Fig. 1B, the electrodes of the second reflector 42 are disposed on both outer sides of the second IDT electrode 22 in the first direction d1.

[0021] As shown in FIG. 2, acoustic wave element 10 includes a piezoelectric layer 100 and electrode layers 110a and 110b that form an IDT electrode and a reflector electrode.

[0022] The electrode layers 110a and 110b are formed by a laminated structure in which a plurality of metals are laminated. For example, the electrode layer 110a constituting the first IDT electrode 11 and the electrode of the first reflector 31 has a laminated structure in which Ti, AlCu (for example, Al containing 1% Cu), and Ti are laminated in this order. The electrode layer 110b constituting the second IDT electrode 22 and the electrode of the second reflector 42 has a laminated structure in which Ti, Pt, and Ti are laminated in this order. In this example, the thickness of the electrode layer 110b is thinner than the thickness of the electrode layer 110a. Also, the density of the electrode layer 110b is higher than the density of the electrode layer 110a.

[0023] The materials constituting the electrode layers 110a and 110b are not limited to the above-mentioned materials. The electrode layers 110a and 110b may not have the above-mentioned laminated structure. The electrode layers 110a and 110b may be composed of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be composed of a laminate of a plurality of layers composed of the above-mentioned metals or alloys. The Ti contained in the electrode layers 110a and 110b has a function of improving adhesion with other layers.

[0024] The acoustic wave element 10 includes a first insulating layer 113 provided on the first principal surface 100a, and a low acoustic velocity layer 153 and a high acoustic velocity support substrate 155 provided on the second principal surface 100b. The first insulating layer 113 is formed on the first principal surface 100a of the piezoelectric layer 100 so as to cover the electrode layer 110a. That is, the first insulating layer 113 is provided on the first principal surface 100a so as to cover the first electrode fingers 11a, 11b of the first IDT electrode 11 and the first reflecting electrode finger 31a of the first reflector 31. The first insulating layer 113 is a layer intended to protect the electrode layer 110a from the external environment, adjust the frequency-temperature characteristics, and increase moisture resistance, and is made of, for example, silicon dioxide (SiO 2It should be noted that the first insulating layer 113 does not necessarily have to be formed.

[0025] The low acoustic velocity layer 153 is formed on the second main surface 100b of the piezoelectric layer 100 so as to cover the electrode layer 110b. The low acoustic velocity layer 153 is an example of the second insulating layer 114. The low acoustic velocity layer 153 is provided on the second main surface 100b so as to cover the second electrode fingers 22a, 22b of the second IDT electrode 22 and the second reflecting electrode finger 42a of the second reflector 42.

[0026] The electrode layer 110b constituting the second IDT electrode 22 and the electrode of the second reflector 42 is embedded in a low acoustic velocity layer 153. The low acoustic velocity layer 153 is a film in which the acoustic velocity of the bulk waves in the low acoustic velocity layer 153 is slower than the acoustic velocity of the acoustic waves propagating through the piezoelectric layer 100, and is disposed between the piezoelectric layer 100 and a high acoustic velocity support substrate 155. This structure and the property of the acoustic wave that the energy is concentrated in a medium with an essentially low acoustic velocity suppress the leakage of the surface acoustic wave energy outside the IDT electrode. The low acoustic velocity layer 153 is made of, for example, silicon dioxide (SiO 2 ) is the main component of the membrane.

[0027] The low acoustic velocity layer 153 may be made of a dielectric material such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or a compound of silicon oxide with fluorine, carbon, or boron, or a material containing the above materials as a main component.

[0028] The high acoustic speed support substrate 155 is a substrate that supports the low acoustic speed layer 153, the piezoelectric layer 100, and the electrode layers 110a and 110b. The high acoustic speed support substrate 155 is a substrate in which the acoustic speed of the bulk waves in the high acoustic speed support substrate 155 is faster than that of the surface waves and boundary waves propagating through the piezoelectric layer 100, and functions to confine the surface acoustic waves in the portion where the piezoelectric layer 100 and the low acoustic speed layer 153 are laminated, and to prevent the surface acoustic waves from leaking below the high acoustic speed support substrate 155. The high acoustic speed support substrate 155 is, for example, a silicon substrate.

[0029] Examples of materials for the high acoustic velocity support substrate 155 include piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectric materials such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; and semiconductors such as silicon. Alternatively, materials containing the above materials as main components may be used. The spinel includes aluminum compounds containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, and the like. Examples of the spinel include MgAl 2 O 4 , FeAl 2 O 4 , ZnAl 2 O 4 , MnAl 2 O 4 The following can be mentioned.

[0030] In addition, the high acoustic velocity support substrate 155 may have a structure in which a support substrate and a high acoustic velocity layer in which the acoustic velocity of the bulk waves propagating through the piezoelectric layer 100 is faster than that of the elastic waves of the surface waves or boundary waves propagating through the piezoelectric layer 100 are laminated.

[0031] In this case, the material of the support substrate may be, for example, a piezoelectric material such as aluminum nitride, lithium tantalate, lithium niobate, or quartz, a ceramic material such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, or forsterite, a dielectric material such as diamond or glass, a semiconductor material such as silicon or gallium nitride, or a resin, or a material mainly composed of the above-mentioned materials. The high acoustic velocity layer may be made of various high acoustic velocity materials such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, DLC film, or diamond, a medium mainly composed of the above-mentioned materials, or a medium mainly composed of a mixture of the above-mentioned materials.

[0032] The laminated structure of the piezoelectric layer 100 makes it possible to significantly increase the Q value of the acoustic wave element at the resonant frequency and the anti-resonant frequency, compared to a structure using a single piezoelectric layer. In other words, a surface acoustic wave resonator with a high Q value can be configured, and therefore a filter with low insertion loss can be configured using the surface acoustic wave resonator.

[0033] Furthermore, by embedding the second IDT electrode 22 in the low acoustic speed layer 153, the piezoelectric layer 100 is supported by the low acoustic speed layer 153 even in the portion where an elastic wave is excited, so that the shape of the piezoelectric layer 100 is less likely to deform, and fluctuations in electrical characteristics can be suppressed. Furthermore, by embedding the second IDT electrode 22 in the low acoustic speed layer 153, higher modes can be leaked to the low acoustic speed layer 153 side. This makes it possible to suppress the occurrence of higher modes.

[0034] In the following description, the acoustic wave propagation direction along the main surface of the piezoelectric layer 100 is defined as a first direction d1, the direction along the main surface of the piezoelectric layer 100 in which the electrode fingers of the IDT electrode extend is defined as a second direction d2, and the direction perpendicular to both the first direction d1 and the second direction d2 is defined as a third direction d3. The second direction d2 is a direction intersecting the first direction d1, and the third direction d3 is a direction perpendicular to the piezoelectric layer 100.

[0035] 1A, the first IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B facing each other. One comb-shaped electrode 11A is composed of a plurality of first electrode fingers 11a arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the first electrode fingers 11a to each other. The other comb-shaped electrode 11B is composed of a plurality of first electrode fingers 11b arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the first electrode fingers 11b to each other. The first electrode fingers 11a and 11b are arranged at a predetermined pitch along the first direction d1.

[0036] The first reflector 31 is disposed adjacent to the first IDT electrode 11 in the first direction d1. The first reflector 31 is composed of a plurality of first reflective electrode fingers 31a disposed to extend in the second direction d2, and a bus bar electrode 31c connecting one ends of the plurality of first reflective electrode fingers 31a to each other. The plurality of first reflective electrode fingers 31a are arranged at a predetermined pitch along the first direction d1.

[0037] 1B, the second IDT electrode 22 has a pair of comb-shaped electrodes 22A and 22B facing each other. One comb-shaped electrode 22A is composed of a plurality of second electrode fingers 22a arranged to extend in the second direction d2 and a busbar electrode 22c connecting one ends of the plurality of second electrode fingers 22a to each other. The other comb-shaped electrode 22B is composed of a plurality of second electrode fingers 22b arranged to extend in the second direction d2 and a busbar electrode 22c connecting one ends of the plurality of second electrode fingers 22b to each other. The plurality of second electrode fingers 22a and 22b are arranged at a predetermined pitch along the first direction d1.

[0038] The second reflector 42 is disposed adjacent to the second IDT electrode 22 in the first direction d1. The second reflector 42 is composed of a plurality of second reflective electrode fingers 42a disposed to extend in the second direction d2, and a bus bar electrode 42c connecting one ends of the plurality of second reflective electrode fingers 42a to each other. The plurality of second reflective electrode fingers 42a are arranged at a predetermined pitch along the first direction d1.

[0039] The first electrode finger 11a and the second electrode finger 22a arranged above and below to sandwich the piezoelectric layer 100 have the same polarity, and the upper and lower first electrode fingers 11b and second electrode fingers 22b have the same polarity.

[0040] FIG. 3 is a cross-sectional view of acoustic wave element 10 taken along line III-III shown in FIGS. 1A and 1B.

[0041] As shown in FIG. 3, first IDT electrode 11 and second IDT electrode 22 of acoustic wave element 10 are connected to each other.

[0042] For example, one comb-shaped electrode 11A included in the first IDT electrode 11 is electrically connected to one comb-shaped electrode 22A included in the second IDT electrode 22. Specifically, a bus bar electrode 11c of one comb-shaped electrode 11A and a bus bar electrode 22c of the other comb-shaped electrode 22A are connected by one via conductor 130A that penetrates the piezoelectric layer 100 in the thickness direction.

[0043] The other comb-like electrode 11B included in the first IDT electrode 11 is electrically connected to the other comb-like electrode 22B included in the second IDT electrode 22. Specifically, the bus bar electrode 11c of the other comb-like electrode 11B and the bus bar electrode 22c of the other comb-like electrode 22B are connected by the other via conductor 130B that penetrates the piezoelectric layer 100 in the thickness direction.

[0044] The two comb-shaped electrodes arranged above and below to sandwich the piezoelectric layer 100 may be electrically connected at the location where the busbar electrode is provided, or may be electrically connected at the locations of the respective lead wires connected to the busbar electrodes. The first reflector 31 and the second reflector 42 arranged above and below to sandwich the piezoelectric layer 100 are not connected by a via conductor or the like, but may both be set to a reference potential (ground).

[0045] In this embodiment, most of the first IDT electrode 11 and the second IDT electrode 22 have the same shape, but the first electrode finger at the end of the first IDT electrode 11 does not face the second electrode finger at the end of the second IDT electrode 22.

[0046] Here, as shown in FIG. 2, the area between the multiple first reflectors 31 in the first direction d1 is defined as the first area m1, the area between the multiple second reflectors 42 in the first direction d1 is defined as the second area m2, and the smallest area including the first area m1 and the second area m2 as viewed from the third direction d3 is defined as the inter-reflector area MR.

[0047] The minimum area including the first area m1 and the second area m2 is the sum of the area where both the first area m1 and the second area m2 exist when viewed from the third direction d3, and the area where only one of the areas exists. If there is no area where only one of the areas exists, the minimum area including the first area m1 and the second area m2 is the area where both the first area m1 and the second area m2 exist. In this example, the first area m1, the second area m2, and the inter-reflector area MR are the same area in the first direction d1.

[0048] 2, in one end region E of the inter-reflector region MR in the first direction d1 (for example, an end region in the negative direction of the first direction d1), first electrode fingers 11a are arranged on the first main surface 100a, but no electrode fingers are arranged on the second main surface 100b. In this example, in a region on the second main surface 100b that is positioned in the third direction d3 as viewed from the first electrode fingers 11a located in one end region E, no second electrode fingers are arranged and a second insulating layer 114 is formed.

[0049] 2, in the other end region E of the inter-reflector region MR in the first direction d1 (for example, the end region in the positive direction of the first direction d1), the first electrode fingers 11a are arranged on the first main surface 100a, but no electrode fingers are arranged on the second main surface 100b. In this example, in the region on the second main surface 100b that is located in the third direction d3 as viewed from the first electrode fingers 11a located in the other end region E, no second electrode fingers are arranged and a second insulating layer 114 is formed.

[0050] That is, acoustic wave element 10 has a region where first electrode fingers 11a, 11b and second electrode fingers 22a, 22b do not face each other in the third direction d3 in one end region E and the other end region E in the first direction d1 of inter-reflector region MR. Note that end region E is a region extending from an edge of inter-reflector region MR in the first direction d1 to a predetermined distance inward, and the predetermined distance is, for example, 10% of the distance of inter-reflector region MR in the first direction d1.

[0051] The first electrode fingers not facing the second electrode fingers in each end region E include at least the first electrode finger, among the multiple first electrode fingers 11a, 11b arranged along the first direction d1, that is closest to the first reflector 31. In the figure, one first electrode finger 11a not facing the second electrode finger is shown in each end region E, but the number of first electrode fingers not facing the second electrode fingers is not limited to one and may be multiple.

[0052] For example, in each end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of first electrode fingers 11a, 11b and first reflective electrode fingers 31a. In other words, in both one end region E and the other end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of first electrode fingers 11a, 11b and first reflective electrode fingers 31a.

[0053] For example, when the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a is 222, the number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in each end region E may be 1, 2, or 5. The number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in both one end region E and the other end region E may be 2, 4, or 10.

[0054] In this way, in the end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b have an area where they do not face each other in the third direction d3, so that ripples can be suppressed from occurring at frequencies higher than the anti-resonance frequency of the acoustic wave element 10.

[0055] [Phase Characteristics, etc. of Acoustic Wave Devices of Examples 1, 2, 3, and 4 and Comparative Example] The phase characteristics and the like of acoustic wave devices 10 of Examples 1, 2, 3, and 4, which are examples of the first embodiment, and acoustic wave device 510 of a comparative example will be described.

[0056] For comparison with each of the embodiments, the configuration of acoustic wave element 510 of the comparative example will be described.

[0057] Fig. 4A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 510 of a comparative example. Fig. 4B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 510. Fig. 5 is a cross-sectional view of acoustic wave element 510 taken along line VV shown in Figs. 4A and 4B.

[0058] The comparative acoustic wave element 510 includes a piezoelectric layer 100, a first IDT electrode 11, a plurality of first reflectors 31, a second IDT electrode 22, a plurality of second reflectors 42, a first insulating layer 113, a low acoustic velocity layer 153, and a high acoustic velocity support substrate 155.

[0059] In acoustic wave element 510 of the comparative example, when viewed from third direction d3, first IDT electrode 11 and second IDT electrode 22 are arranged at the same position, and first reflector 31 and second reflector 42 are arranged at the same position. In other words, when viewed from third direction d3, first IDT electrode 11 and second IDT electrode 22 overlap, and first reflector 31 and second reflector 42 overlap.

[0060] On the other hand, in the acoustic wave element 10 of Examples 1 to 4, when viewed from the third direction d3, the first IDT electrode 11 and the second IDT electrode 22 overlap except in the end region E of the inter-reflector region MR, but do not overlap in the end region E, and the first reflector 31 and the second reflector 42 overlap.

[0061] In acoustic wave devices 10 of Examples 1 to 4 and acoustic wave device 510 of the comparative example, the wavelengths λ of first IDT electrode 11 and second IDT electrode 22 are IDTis 1 μm. Since the arrangement pitch of the electrode fingers arranged along the first direction d1 is half the wavelength, the arrangement pitch of the first electrode fingers 11a, 11b, the arrangement pitch of the second electrode fingers 22a, 22b, the arrangement pitch of the first reflective electrode fingers 31a, and the arrangement pitch of the second reflective electrode fingers 42a are each 0.5 μm. The thickness of the piezoelectric layer 100 is 0.2λ IDT and the thickness of the first IDT electrode 11 is 0.015λ IDT and the thickness of the second IDT electrode 22 is 0.018λ IDT The thickness of the first insulating layer 113 is 0.015λ IDT and the thickness of the low acoustic velocity layer 153 (second insulating layer 114) is 0.218λ IDT and the thickness of the high acoustic velocity support substrate 155 is 0.45λ IDT The thickness of the low acoustic velocity layer 153 is the thickness at a portion where the second electrode fingers 22a, 22b of the second IDT electrode 22 are not provided, that is, at a portion in contact with the second main surface 100b.

[0062] Fig. 6A is a graph showing phase characteristics of acoustic wave devices according to Examples 1, 2, 3, and 4 and a comparative example, Fig. 6B is an enlarged view of a portion VIB in Fig. 6A, and Fig. 6C is an enlarged view of a portion VIC in Fig. 6A.

[0063] FIG. 6A shows the phase characteristics when a high-frequency signal is input to the IDT electrode from one of the comb-shaped electrodes (busbar electrode) of the acoustic wave element. In this case, the other comb-shaped electrode is short-circuited. In FIG. 6A, the region above 0 on the vertical axis shows that the impedance of the acoustic wave element is inductive, and the region below 0 shows that the impedance of the acoustic wave element is capacitive. In the figure, ripples, which are unwanted waves, appear on the higher frequency side than the band where the impedance is inductive (the band between the resonant frequency and the anti-resonant frequency).

[0064] Fig. 6B shows an enlarged view of the phase in a band on the higher frequency side than the band where the impedance of the acoustic wave element is inductive. Fig. 6C shows an enlarged view of the phase in a band where the impedance of the acoustic wave element is inductive. Figs. 6A to 6C show the numbers of first electrode fingers and second electrode fingers that do not face each other in one end region E.

[0065] 6B, in acoustic wave elements 10 of Examples 1 to 4, ripples occurring at higher frequencies than the band in which the impedance is inductive are smaller than those in the acoustic wave element of the comparative example. In addition, the ripples become smaller as the number of electrode fingers that are not opposed to each other increases in the order of Examples 1, 2, 3, and 4. The reason why the ripples become smaller is believed to be that the Bragg reflection by the reflector is suppressed as the number of electrode fingers that are not opposed to each other increases. In this way, by increasing the number of electrode fingers that are not opposed to each other in the third direction d3 in the end region E of inter-reflector region MR in the first direction d1, it is possible to suppress the occurrence of ripples at higher frequencies than the band in which the impedance of acoustic wave element 10 is inductive.

[0066] In addition, in Examples 1 to 4 shown in Fig. 6C, the value of the phase representing the inductivity is small in some bands, but this can be addressed by other methods. For example, by using acoustic wave element 10 of Examples 1 to 4 as a parallel arm resonator that forms a low frequency band of the pass band of a ladder-type bandpass filter, it is possible to reduce the influence of the phase change representing the inductivity on the pass band of the bandpass filter. Even when acoustic wave element 10 is used as a series arm resonator, by forming a pass band including other series arm resonators, it is possible to reduce the influence of the phase change representing the inductivity on the pass band of the bandpass filter.

[0067] [First Modification of First Embodiment] 7A to 8, acoustic wave element 10A according to a first modification of the first embodiment will be described. In the first modification, an example will be described in which second electrode fingers at an end of second IDT electrode 22 do not face first electrode fingers at an end of first IDT electrode 11.

[0068] Fig. 7A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 10A according to a first modification of embodiment 1. Fig. 7B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 10A. Fig. 8 is a cross-sectional view of acoustic wave element 10A taken along line VIII-VIII shown in Figs. 7A and 7B.

[0069] 7A, 7B, and 8 includes a piezoelectric layer 100, a first IDT electrode 11, a plurality of first reflectors 31, a second IDT electrode 22, a plurality of second reflectors 42, a first insulating layer 113, a low acoustic velocity layer 153 (second insulating layer 114), and a high acoustic velocity support substrate 155. In this example, the first region m1, the second region m2, and the inter-reflector region MR are the same region in the first direction d1.

[0070] 8, in one end region E of the inter-reflector region MR in the first direction d1, second electrode fingers 22a are arranged on the second main surface 100b, but no electrode fingers are arranged on the first main surface 100a. In this example, in a region on the first main surface 100a that is positioned in the third direction d3 as viewed from the second electrode fingers 22a located in one end region E, no first electrode fingers are arranged and a first insulating layer 113 is formed.

[0071] 8, in the other end region E of the inter-reflector region MR in the first direction d1, second electrode fingers 22a are arranged on the second main surface 100b, but no electrode fingers are arranged on the first main surface 100a. In this example, in the region on the first main surface 100a, in the region positioned in the third direction d3 as viewed from the second electrode fingers 22a positioned in the other end region E, no first electrode fingers are arranged and a first insulating layer 113 is formed.

[0072] In other words, acoustic wave element 10A has areas in both end regions E and E of inter-reflector region MR in the first direction d1 where first electrode fingers 11a, 11b and second electrode fingers 22a, 22b do not face each other in the third direction d3.

[0073] The second electrode fingers not facing the first electrode fingers in each end region E include at least the second electrode finger closest to the second reflector 42, among the multiple second electrode fingers 22a, 22b arranged along the first direction d1. In the figure, one second electrode finger 22a not facing the first electrode finger is shown in each end region E, but the number of second electrode fingers not facing the first electrode finger is not limited to one, and may be multiple.

[0074] For example, in each end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of second electrode fingers 22a, 22b and second reflective electrode fingers 42a. In other words, in both one end region E and the other end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of second electrode fingers 22a, 22b and second reflective electrode fingers 42a.

[0075] For example, when the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a is 222, the number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in each end region E may be 1, 2, or 5. The number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in both one end region E and the other end region E may be 2, 4, or 10.

[0076] In this way, in the end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b have an area where they do not face each other in the third direction d3, so that ripples can be suppressed from occurring at frequencies higher than the anti-resonance frequency of the acoustic wave element 10A.

[0077] [Modification 2 of the First Embodiment] 9A to 10, an acoustic wave element 10B according to a second modification of the first embodiment will be described. In the second modification, the first reflector 31 has first reflecting electrode fingers that do not face the second reflecting electrode fingers that face the second reflector 42.

[0078] Fig. 9A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 10B in accordance with Modification 2 of Embodiment 1. Fig. 9B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 10B. Fig. 10 is a cross-sectional view of acoustic wave element 10B taken along line XX shown in Figs. 9A and 9B.

[0079] 9A, 9B, and 10 includes a piezoelectric layer 100, a first IDT electrode 11, a plurality of first reflectors 31, a second IDT electrode 22, a plurality of second reflectors 42, a first insulating layer 113, a low acoustic velocity layer 153 (second insulating layer 114), and a high acoustic velocity support substrate 155. In this example, the second region m2 and the inter-reflector region MR are the same region in the first direction d1.

[0080] 10, in one end region E of the inter-reflector region MR in the first direction d1, the first reflective electrode fingers 31a are arranged on the first main surface 100a, but no reflective electrode fingers are arranged on the second main surface 100b. In this example, in a region on the second main surface 100b located in the third direction d3 as viewed from the first reflective electrode fingers 31a located in one end region E, no second reflective electrode fingers are arranged and a second insulating layer 114 is formed.

[0081] 10, in the other end region E of the inter-reflector region MR in the first direction d1, the first reflective electrode fingers 31a are arranged on the first main surface 100a, but no reflective electrode fingers are arranged on the second main surface 100b. In this example, in the region on the second main surface 100b located in the third direction d3 as viewed from the first reflective electrode fingers 31a located in the other end region E, no second reflective electrode fingers are arranged and a second insulating layer 114 is formed.

[0082] In other words, the acoustic wave element 10B has regions in both end regions E and E of the inter-reflector region MR in the first direction d1 where the first reflective electrode fingers 31a and the second reflective electrode fingers 42a do not face each other in the third direction d3.

[0083] The first reflective electrode fingers not facing the second reflective electrode fingers in each end region E include at least a first reflective electrode finger, among the multiple first reflective electrode fingers 31a arranged along the first direction d1, that is closest to the first IDT electrode 11. In the figure, one first reflective electrode finger 31a not facing the second reflective electrode finger is shown in each end region E, but the number of first reflective electrode fingers not facing the second reflective electrode fingers is not limited to one and may be multiple.

[0084] For example, in each end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a. In other words, in both one end region E and the other end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a.

[0085] For example, when the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a is 222, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in each end region E may be 1, 2, or 5. The number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in both one end region E and the other end region E may be 2, 4, or 10.

[0086] In this way, in the end region E in the first direction d1 of the inter-reflector region MR, the first reflecting electrode finger 31a and the second reflecting electrode finger 42a have a region where they do not face each other in the third direction d3, so that ripples can be suppressed from occurring at frequencies higher than the anti-resonance frequency of the acoustic wave element 10B.

[0087] [Third Modification of First Embodiment] 11A to 12, an acoustic wave device 10C according to a third modification of the first embodiment will be described. In the third modification, the second reflector 42 does not face the first reflector 31.

[0088] Fig. 11A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 10C in accordance with Modification 3 of Embodiment 1. Fig. 11B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 10C. Fig. 12 is a cross-sectional view of acoustic wave element 10C taken along line XII-XII shown in Figs. 11A and 11B.

[0089] 11A, 11B, and 12 includes a piezoelectric layer 100, a first IDT electrode 11, a plurality of first reflectors 31, a second IDT electrode 22, a plurality of second reflectors 42, a first insulating layer 113, a low acoustic velocity layer 153 (second insulating layer 114), and a high acoustic velocity support substrate 155. In this example, a first region m1 and an inter-reflector region MR are the same region in a first direction d1.

[0090] 12, in one end region E of the inter-reflector region MR in the first direction d1, the second reflective electrode fingers 42a are arranged on the second main surface 100b, but no reflective electrode fingers are arranged on the first main surface 100a. In this example, in a region on the first main surface 100a that is positioned in the third direction d3 as viewed from the second reflective electrode fingers 42a located in one end region E, no first reflective electrode fingers are arranged and a first insulating layer 113 is formed.

[0091] 12, in the other end region E of the inter-reflector region MR in the first direction d1, the second reflective electrode fingers 42a are arranged on the second main surface 100b, but no reflective electrode fingers are arranged on the first main surface 100a. In this example, in the region on the first main surface 100a that is positioned in the third direction d3 as viewed from the second reflective electrode fingers 42a located in the other end region E, no first reflective electrode fingers are arranged and a first insulating layer 113 is formed.

[0092] In other words, the acoustic wave element 10C has regions in both end regions E and E of the inter-reflector region MR in the first direction d1 where the first reflective electrode fingers 31a and the second reflective electrode fingers 42a do not face each other in the third direction d3.

[0093] The second reflective electrode fingers not facing the first reflective electrode fingers in each end region E include at least a second reflective electrode finger, among the multiple second reflective electrode fingers 42a arranged along the first direction d1, that is closest to the second IDT electrode 22. In the figure, one second reflective electrode finger 42a not facing the first reflective electrode finger is shown in each end region E, but the number of second reflective electrode fingers not facing the first reflective electrode fingers is not limited to one and may be multiple.

[0094] For example, in each end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a. In other words, in both one end region E and the other end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a.

[0095] For example, when the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a is 222, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in each end region E may be 1, 2 or 5. The number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in both one end region E and the other end region E may be 2, 4 or 10.

[0096] In this way, in the end region E of the inter-reflector region MR in the first direction d1, the first reflecting electrode finger 31a and the second reflecting electrode finger 42a have a region where they do not face each other in the third direction d3, so that ripples can be suppressed from occurring at frequencies higher than the anti-resonance frequency of the acoustic wave element 10C.

[0097] [Fourth Modification of the First Embodiment] 13A to 14, an acoustic wave element 10D according to a fourth modification of the first embodiment will be described. In the fourth modification, a first electrode finger at an end of a first IDT electrode 11 does not face a second electrode finger at an end of a second IDT electrode 22, but faces a second reflecting electrode finger at an end of a second reflector.

[0098] Fig. 13A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 10D in accordance with Modification 4 of Embodiment 1. Fig. 13B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 10D. Fig. 14 is a cross-sectional view of acoustic wave element 10D taken along line XIV-XIV shown in Figs. 13A and 13B.

[0099] 13A, 13B, and 14 includes a piezoelectric layer 100, a first IDT electrode 11, a plurality of first reflectors 31, a second IDT electrode 22, a plurality of second reflectors 42, a first insulating layer 113, a low acoustic velocity layer 153 (second insulating layer 114), and a high acoustic velocity support substrate 155. In this example, a first region m1 and an inter-reflector region MR are the same region in a first direction d1.

[0100] 14, in one end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11a are arranged on the first main surface 100a, but the second electrode fingers are not arranged on the second main surface 100b. In this example, in a region on the second main surface 100b that is positioned in the third direction d3 as viewed from the first electrode fingers 11a located in one end region E, the second electrode fingers are not arranged, and the second reflective electrode fingers 42a are arranged instead.

[0101] 14, in the other end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11a are arranged on the first main surface 100a, but the second electrode fingers are not arranged on the second main surface 100b. In this example, in the region on the second main surface 100b that is positioned in the third direction d3 as viewed from the first electrode fingers 11a located in the other end region E, the second electrode fingers are not arranged, and the second reflecting electrode fingers 42a are arranged instead.

[0102] In other words, acoustic wave element 10D has, in both end regions E and the other end region E in the first direction d1 of inter-reflector region MR, regions where first electrode fingers 11a, 11b and second electrode fingers 22a, 22b do not face each other in the third direction d3, and regions where first reflective electrode finger 31a and second reflective electrode finger 42a do not face each other in the third direction d3.

[0103] For example, in each end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of first electrode fingers 11a, 11b and first reflective electrode fingers 31a. In other words, in both one end region E and the other end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of first electrode fingers 11a, 11b and first reflective electrode fingers 31a.

[0104] For example, in each end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a. In other words, in both one end region E and the other end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a.

[0105] For example, when the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a is 222, the number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in each end region E may be 1, 2, or 5. The number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in both one end region E and the other end region E may be 2, 4, or 10.

[0106] For example, when the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a is 222, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in each end region E may be 1, 2 or 5. The number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in both one end region E and the other end region E may be 2, 4 or 10.

[0107] In this way, in the end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b have an area where they do not face each other in the third direction d3, and the first reflective electrode finger 31a and the second reflective electrode finger 42a have an area where they do not face each other in the third direction d3, thereby suppressing the occurrence of ripples at a frequency higher than the anti-resonance frequency of the acoustic wave element 10D.

[0108] [Fifth Modification of the First Embodiment] 15A to 16, an acoustic wave element 10E according to a fifth modification of the first embodiment will be described. In the fifth modification, the second electrode fingers at the end of the second IDT electrode 22 do not face the first electrode fingers at the end of the first IDT electrode 11, but face the first reflecting electrode fingers at the end of the first reflector.

[0109] Fig. 15A is a top view of first IDT electrode 11 and first reflector 31 of acoustic wave element 10E in accordance with Modification 5 of Embodiment 1. Fig. 15B is a top view of second IDT electrode 22 and second reflector 42 of acoustic wave element 10E. Fig. 16 is a cross-sectional view of acoustic wave element 10E taken along line XVI-XVI shown in Figs. 15A and 15B.

[0110] 15A, 15B, and 16 includes a piezoelectric layer 100, a first IDT electrode 11, a plurality of first reflectors 31, a second IDT electrode 22, a plurality of second reflectors 42, a first insulating layer 113, a low acoustic velocity layer 153 (second insulating layer 114), and a high acoustic velocity support substrate 155. In this example, the second region m2 and the inter-reflector region MR are the same region in the first direction d1.

[0111] 16, in one end region E of the inter-reflector region MR in the first direction d1, the second electrode fingers 22a are arranged on the second main surface 100b, but the first electrode fingers are not arranged on the first main surface 100a. In this example, in a region on the first main surface 100a that is positioned in the third direction d3 as viewed from the second electrode fingers 22a located in one end region E, the first electrode fingers are not arranged, and the first reflecting electrode fingers 31a are arranged instead.

[0112] 16, in the other end region E of the inter-reflector region MR in the first direction d1, the second electrode fingers 22a are arranged on the second main surface 100b, but the first electrode fingers are not arranged on the first main surface 100a. In this example, in the region on the first main surface 100a, in the region positioned in the third direction d3 as viewed from the second electrode fingers 22a positioned in the other end region E, the first electrode fingers are not arranged, and the first reflecting electrode fingers 31a are arranged instead.

[0113] In other words, acoustic wave element 10E has, in both end regions E and the other end region E in the first direction d1 of inter-reflector region MR, regions where first electrode fingers 11a, 11b and second electrode fingers 22a, 22b do not face each other in the third direction d3, and regions where first reflective electrode finger 31a and second reflective electrode finger 42a do not face each other in the third direction d3.

[0114] For example, in each end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of second electrode fingers 22a, 22b and second reflective electrode fingers 42a. In other words, in both one end region E and the other end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of second electrode fingers 22a, 22b and second reflective electrode fingers 42a.

[0115] For example, in each end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 2.5% of the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a. In other words, in both one end region E and the other end region E, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other is desirably within a range of more than 0% and not more than 5% of the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a.

[0116] For example, when the total number of the second electrode fingers 22a, 22b and the second reflective electrode fingers 42a is 222, the number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in each end region E may be 1, 2, or 5. The number of the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b that do not face each other in both one end region E and the other end region E may be 2, 4, or 10.

[0117] For example, when the total number of the first electrode fingers 11a, 11b and the first reflective electrode fingers 31a is 222, the number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in each end region E may be 1, 2, or 5. The number of the first reflective electrode fingers 31a and the second reflective electrode fingers 42a that do not face each other in both one end region E and the other end region E may be 2, 4, or 10.

[0118] In this way, in the end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b have an area where they do not face each other in the third direction d3, and the first reflective electrode finger 31a and the second reflective electrode finger 42a have an area where they do not face each other in the third direction d3, thereby suppressing the occurrence of ripples at frequencies higher than the anti-resonance frequency of the acoustic wave element 10E.

[0119] (Embodiment 2) In the second embodiment, a ladder-type acoustic wave filter device using acoustic wave element 10 according to the first embodiment will be described.

[0120] 17 is a diagram illustrating a circuit configuration of an acoustic wave filter device 1 according to Embodiment 2. As illustrated in the diagram, the acoustic wave filter device 1 includes series arm resonators s11, s12, s13, s14, and s15, parallel arm resonators p11, p12, p13, and p14, and terminals 50 and 60.

[0121] The series arm resonators s11 to s15 are connected in series between the terminal 50 and the terminal 60. The parallel arm resonators p11 to p14 are connected in parallel between the connection points of the terminal 50, the series arm resonators s11 to s15, and the terminal 60 and the reference terminal (ground), respectively. With the above-described connection configuration of the series arm resonators s11 to s15 and the parallel arm resonators p11 to p14, the acoustic wave filter device 1 forms a ladder-type bandpass filter. Note that circuit elements such as inductors may be inserted between the parallel arm resonators p11 to p14 and the ground.

[0122] In the second embodiment, all of the series arm resonators s11 to s15 and the parallel arm resonators p11 to p14 of the resonators included in the elastic wave filter device 1 may be configured by the above-described elastic wave element 10. Alternatively, only the parallel arm resonators p11 to p14 of the resonators included in the elastic wave filter device 1 may be configured by the above-described elastic wave element 10. Alternatively, of the resonators included in the elastic wave filter device 1, only the parallel arm resonator p14 or the series arm resonator s15 that is closest to the terminal 50 connected to the common terminal may be configured by the above-described elastic wave element 10.

[0123] The acoustic wave filter device 1 may have any configuration as long as it includes the configuration of the acoustic wave element according to the first embodiment. The circuit configuration shown in Fig. 17 is only one example, and the number of series arm resonators, the number of parallel arm resonators, the connection points of the inductors, and the like are not limited to the configuration in Fig. 17. Although a ladder-type circuit configuration is illustrated in Fig. 17, a longitudinally coupled resonator circuit may be included.

[0124] (Embodiment 3) In the third embodiment, a multiplexer is shown having a configuration in which a plurality of filters, each including the acoustic wave filter device 1 according to the second embodiment, are connected directly or indirectly to a common terminal.

[0125] 18 is a circuit diagram of a multiplexer 5 and its peripheral circuit (antenna 4) according to Embodiment 3. The multiplexer 5 shown in the figure includes an acoustic wave filter device 1, a filter 3, a common terminal 70, and input / output terminals 81 and 82.

[0126] In the acoustic wave filter device 1 , a terminal 50 of the acoustic wave filter device 1 is connected to a common terminal 70 , and a terminal 60 of the acoustic wave filter device 1 is connected to an input / output terminal 81 .

[0127] The filter 3 is connected to a common terminal 70 and an input / output terminal 82. The filter 3 is, for example, a ladder-type acoustic wave filter having parallel arm resonators and series arm resonators, but may be an LC filter or the like, and the circuit configuration is not particularly limited.

[0128] The passband of the acoustic wave filter device 1 is located at a lower frequency than the passband of the filter 3 .

[0129] The acoustic wave filter device 1 and the filter 3 do not have to be directly connected to the common terminal 70 as shown in FIG. 18, but may be indirectly connected to the common terminal 70 via, for example, an impedance matching circuit, a phase shifter, a circulator, or a switch element capable of selecting two or more filters.

[0130] In this embodiment, the multiplexer 5 has a circuit configuration in which two filters are connected to the common terminal 70, but the number of filters connected to the common terminal 70 is not limited to two and may be three or more.

[0131] In other words, the multiplexer of the present invention comprises a plurality of filters including an elastic wave filter device 1, and the input / output terminals and one of the input / output terminals of each of the plurality of filters are directly or indirectly connected to a common terminal, and at least one of the plurality of filters excluding the elastic wave filter device 1 may have a passband higher in frequency than the passband of the elastic wave filter device 1.

[0132] (summary) The configurations of acoustic wave elements 10, 10A, 10B, 10C, 10D, and 10E, acoustic wave filter device 1, and multiplexer 5 according to an embodiment of the present invention will be exemplified below.

[0133] The acoustic wave element of Example 1 includes a first IDT electrode 11 and a plurality of first reflectors 31 formed on a first main surface 100a of a piezoelectric layer 100, and a second IDT electrode 22 and a plurality of second reflectors 42 formed on a second main surface 100b facing away from the first main surface 100a of the piezoelectric layer 100. The first IDT electrode 11 has a plurality of first electrode fingers 11a, 11b arranged to extend in a second direction d2 intersecting with the first direction d1 in a direction along the first main surface 100a. Each of the plurality of first reflectors 31 has a plurality of first reflecting electrode fingers 31a arranged to extend in the second direction d2 and to be disposed on both outer sides of the first IDT electrode 11 in the first direction d1. The second IDT electrode 22 has a plurality of second electrode fingers 22a, 22b arranged to extend in a second direction d2 intersecting the first direction d1 in a direction along the second main surface 100b. Each of the plurality of second reflectors 42 has a plurality of second reflective electrode fingers 42a arranged to extend in the second direction d2 and to be disposed on both outer sides of the second IDT electrode 22 in the first direction d1. If a region between the plurality of first reflectors 31 in the first direction d1 is defined as a first region m1, a region between the plurality of second reflectors 42 in the first direction d1 is defined as a second region m2, and a minimum region including the first region m1 and the second region m2 as viewed from a third direction d3 perpendicular to both the first direction d1 and the second direction d2 is defined as an inter-reflector region MR, (1) In an end region E of the inter-reflector region MR in the first direction d1, the first electrode fingers 11 a, 11 b and the second electrode fingers 22 a, 22 b have a region where they do not face each other in the third direction d3, or (2) In the end regions E in the first direction d1 of the inter-reflector region MR, the first reflective electrode fingers 31a and the second reflective electrode fingers 42a have regions where they do not face each other in the third direction d3.

[0134] As described above in (1), by having an area in the end region E of the inter-reflector region MR in the first direction d1 where the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b do not face each other in the third direction d3, it is possible to suppress the generation of ripples at frequencies higher than the anti-resonance frequency of the acoustic wave element. Alternatively, as described above in (2), by having an area in the end region E of the inter-reflector region MR in the first direction d1 where the first reflecting electrode finger 31a and the second reflecting electrode finger 42a do not face each other in the third direction d3, it is possible to suppress the generation of ripples at frequencies higher than the anti-resonance frequency of the acoustic wave element.

[0135] Acoustic wave element 10 of Example 2 is the acoustic wave element of Example 1, and further includes a second insulating layer 114 formed on second main surface 100b so as to cover second electrode fingers 22a, 22b and second reflecting electrode fingers 42a. In a region on second main surface 100b that is positioned in third direction d3 as viewed from a first electrode finger (e.g., 11a) positioned in end region E, no second electrode finger may be arranged and second insulating layer 114 may be formed.

[0136] In this manner, by forming second insulating layer 114 in a region located in third direction d3 as viewed from the first electrode finger located in end region E, a region in which the first electrode finger and the second electrode finger do not face each other in third direction d3 can be formed. This makes it possible to suppress the occurrence of ripples at frequencies higher than the anti-resonance frequency of acoustic wave element 10.

[0137] Acoustic wave element 10A of Example 3 is the acoustic wave element of Example 1, and further includes a first insulating layer 113 formed on first main surface 100a so as to cover first electrode fingers 11a, 11b and first reflecting electrode fingers 31a. In a region on first main surface 100a that is positioned in third direction d3 as viewed from second electrode fingers (e.g., 22a) positioned in end region E, no first electrode fingers may be arranged and first insulating layer 113 may be formed.

[0138] In this manner, by forming first insulating layer 113 in a region located in third direction d3 as viewed from second electrode finger located in end region E, a region in which the first electrode finger and the second electrode finger do not face each other in third direction d3 can be formed, which can suppress the generation of ripples at frequencies higher than the anti-resonance frequency of acoustic wave device 10A.

[0139] Acoustic wave element 10B of Example 4 is the acoustic wave element of Example 1, and further includes a second insulating layer 114 formed on second main surface 100b so as to cover second electrode fingers 22a, 22b and second reflective electrode fingers 42a. In a region on second main surface 100b that is positioned in third direction d3 as viewed from first reflective electrode fingers (e.g., 31a) positioned in end region E, no second reflective electrode fingers may be arranged and second insulating layer 114 may be formed.

[0140] In this manner, by forming second insulating layer 114 in a region located in the third direction d3 as viewed from the first reflective electrode finger located in end region E, a region in which the first reflective electrode finger and the second reflective electrode finger do not face each other in the third direction d3 can be formed, which can suppress the generation of ripples at frequencies higher than the anti-resonance frequency of acoustic wave device 10B.

[0141] Acoustic wave element 10C of Example 5 is the acoustic wave element of Example 1, and further includes a first insulating layer 113 formed on first main surface 100a so as to cover first electrode fingers 11a, 11b and first reflective electrode fingers 31a. In a region on first main surface 100a that is positioned in third direction d3 as viewed from second reflective electrode fingers (e.g., 42a) positioned in end region E, no first reflective electrode fingers may be arranged and first insulating layer 113 may be formed.

[0142] In this manner, by forming first insulating layer 113 in a region located in the third direction d3 as viewed from the second reflective electrode finger located in end region E, a region in which the first reflective electrode finger and the second reflective electrode finger do not face each other in the third direction d3 can be formed, which can suppress the generation of ripples at frequencies higher than the anti-resonance frequency of acoustic wave device 10C.

[0143] The elastic wave element of Example 6 is the elastic wave element of Example 1, and may have an area in an end region E of the inter-reflector region MR in the first direction d1 where the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b do not face each other in the third direction d3, and may have an area where the first reflective electrode finger 31a and the second reflective electrode finger 42a do not face each other in the third direction d3.

[0144] In this way, the first electrode fingers 11a, 11b and the second electrode fingers 22a, 22b have regions where they do not face each other in the third direction d3, and the first reflective electrode finger 31a and the second reflective electrode finger 42a have regions where they do not face each other in the third direction d3, thereby making it possible to suppress the occurrence of ripples at frequencies higher than the anti-resonance frequency of the acoustic wave element.

[0145] Acoustic wave element 10D of Example 7 is the acoustic wave element described in Example 6, and in the region on second main surface 100b that is positioned in third direction d3 as viewed from first electrode finger (e.g., 11a) positioned in end region E, second electrode fingers may not be arranged, but second reflective electrode fingers 42a may be arranged.

[0146] In this manner, by arranging second reflective electrode finger 42a in a region located in third direction d3 as viewed from the first electrode finger located in end region E, a region in which the first and second electrode fingers do not face each other in the third direction d3 can be formed, and a region in which the first and second reflective electrode fingers do not face each other in the third direction d3 can be formed. This makes it possible to suppress the generation of ripples at frequencies higher than the anti-resonance frequency of acoustic wave device 10D.

[0147] Acoustic wave element 10E of Example 8 is the acoustic wave element described in Example 6, and in the region on first main surface 100a that is positioned in third direction d3 as viewed from second electrode finger (e.g., 22a) positioned in end region E, first electrode fingers may not be arranged, but first reflective electrode fingers 31a may be arranged.

[0148] In this manner, by arranging first reflective electrode finger 31a in a region located in third direction d3 as viewed from second electrode finger located in end region E, a region in which the first and second electrode fingers do not face each other in third direction d3 can be formed, and a region in which the first and second reflective electrode fingers do not face each other in third direction d3 can be formed. This makes it possible to suppress the generation of ripples at a frequency higher than the anti-resonance frequency of acoustic wave element 10E.

[0149] An acoustic wave element of Example 9 is the acoustic wave element of any of Examples 1 to 8, in which the end region E has one end region E and the other end region E in the first direction d1 of the inter-reflector region MR. In the one end region E and the other end region E, the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that do not face each other may be more than 0% and not more than 5% of the total number of first electrode fingers 11a, 11b and first reflective electrode fingers 31a or the total number of second electrode fingers 22a, 22b and second reflective electrode fingers 42a.

[0150] By setting the number of first electrode fingers 11a, 11b and second electrode fingers 22a, 22b that are not opposed to each other within the above range, it is possible to suppress the occurrence of ripples on the high frequency side of the anti-resonance frequency of the acoustic wave element. Furthermore, by setting the number of electrode fingers that are not opposed to each other to 5% or less, it is possible to suppress the phase value that represents the inductivity of the impedance of the acoustic wave element from becoming smaller than necessary. Furthermore, by setting the number of electrode fingers that are not opposed to each other to 5% or less, it is possible to suppress the inductive impedance of the acoustic wave element from changing into capacitive impedance.

[0151] An acoustic wave element of Example 10 is the acoustic wave element of any of Examples 1 to 8, in which the end region E has one end region E and the other end region E in the first direction d1 of the inter-reflector region MR. In the one end region E and the other end region E, the number of first reflective electrode fingers 31a and second reflective electrode fingers 42a that do not face each other may be more than 0% and not more than 5% of the total number of first electrode fingers 11a, 11b and first reflective electrode fingers 31a, or the total number of second electrode fingers 22a, 22b and second reflective electrode fingers 42a.

[0152] By setting the number of first reflecting electrode fingers 31a and second reflecting electrode fingers 42a that are not opposed to each other within the above range, it is possible to suppress the occurrence of ripples on the high frequency side of the anti-resonant frequency of the acoustic wave element. Furthermore, by setting the number of reflecting electrode fingers that are not opposed to each other to 5% or less, it is possible to suppress the phase value that represents the inductivity of the impedance of the acoustic wave element from becoming smaller than necessary. Furthermore, by setting the number of reflecting electrode fingers that are not opposed to each other to 5% or less, it is possible to suppress the inductive impedance of the acoustic wave element from changing into capacitive impedance.

[0153] The acoustic wave element of Example 11 is the acoustic wave element according to any one of Examples 1 to 10, and further includes a high acoustic speed support substrate 155 having a bulk wave velocity faster than the acoustic wave velocity propagating through the piezoelectric layer 100, and a low acoustic speed layer 153 disposed between the high acoustic speed support substrate 155 and the piezoelectric layer 100 and having a bulk wave velocity slower than the acoustic wave velocity propagating through the piezoelectric layer 100. The low acoustic speed layer 153 may be provided on the second main surface 100b so as to cover the second IDT electrode 22.

[0154] In this way, by embedding the second IDT electrode 22 in the low acoustic velocity layer 153, the piezoelectric layer 100 is supported by the low acoustic velocity layer 153 even in the portion where an elastic wave is excited, so that the shape of the piezoelectric layer 100 is less likely to deform, and fluctuations in electrical characteristics can be suppressed. Furthermore, by embedding the second IDT electrode 22 in the low acoustic velocity layer 153, it is possible to leak higher modes to the low acoustic velocity layer 153 side. This makes it possible to suppress the occurrence of higher modes.

[0155] The acoustic wave filter device 1 of the twelfth example includes the acoustic wave element 10 of any one of the first to eleventh examples.

[0156] This makes it possible to provide an acoustic wave filter device 1 that uses an acoustic wave element that can suppress the occurrence of ripples on the higher frequency side than the anti-resonance frequency.

[0157] The multiplexer 5 of Example 13 includes a plurality of filters 3 including the acoustic wave filter device 1 of Example 12. One of the input / output terminal 81 and the input / output terminal 82 of each of the plurality of filters 3 is directly or indirectly connected to the common terminal 70, and at least one of the plurality of filters 3 except for the acoustic wave filter device 1 has a passband higher in frequency than the passband of the acoustic wave filter device 1.

[0158] As a result, in the acoustic wave filter device 1, the attenuation in the attenuation band on the higher frequency side than the passband can be increased, thereby reducing the insertion loss in the passband of a filter having a passband on the higher frequency side than the passband of the acoustic wave filter device 1.

[0159] (Other embodiments, etc.) Although the acoustic wave element, acoustic wave filter device, and multiplexer according to the embodiment of the present invention have been described above with reference to the embodiment and examples, the acoustic wave element, acoustic wave filter device, and multiplexer according to the present invention are not limited to the above embodiment and examples. The present invention also includes other embodiments realized by combining any of the components in the above embodiment and examples, examples obtained by applying various modifications to the above embodiment that would occur to those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the acoustic wave element, acoustic wave filter device, and multiplexer disclosed herein.

[0160] For example, the acoustic wave filter device 1 according to a preferred embodiment of the present invention may further include circuit elements such as an inductor and a capacitor.

[0161] Furthermore, the acoustic wave element according to the present invention does not have to be a surface acoustic wave resonator as in the first embodiment, and may be an acoustic wave resonator that uses boundary acoustic waves.

[0162] In the above, an example is shown in which a low acoustic velocity layer 153 and a high acoustic velocity support substrate 155 are provided on the second main surface 100b side of the piezoelectric layer 100, but this is not limited to this, and only a support substrate may be provided on the second main surface 100b side of the piezoelectric layer 100.

[0163] 1A, 1B, 2, and 3 are shown only to illustrate a typical structure of the acoustic wave element 10, and the number and length of the electrode fingers constituting the electrodes are not limited to these. The materials of the layers exemplified in the above laminated structure of the piezoelectric layer 100 and the like are merely examples, and may be changed depending on, for example, important characteristics among the required high-frequency propagation characteristics.

[0164] In the above description of the embodiment, the arrangement pitch of the electrode fingers refers to, for example, the center-to-center distance in the first direction d1 between adjacent first electrode fingers 11a, 11b in the first IDT electrode 11. The same applies to the second IDT electrode 22. The arrangement pitch of the reflective electrode fingers refers to, for example, the center-to-center distance in the first direction d1 between adjacent first reflective electrode fingers 31a in the first reflector 31. The same applies to the second reflector 42. [Industrial Applicability]

[0165] INDUSTRIAL APPLICABILITY The present invention can be widely used in communication devices such as mobile phones as a low-loss, small-sized acoustic wave element, an acoustic wave filter and a multiplexer that can be applied to multi-band and multi-mode frequency standards. [Explanation of symbols]

[0166] 1. Elastic wave filter device 3. Filters 4 Antennas 5 Multiplexer 10, 10A, 10B, 10C, 10D, 10E Acoustic Wave Device 11 First IDT electrode 11A, 11B comb-shaped electrode 11a, 11b 1st electrode finger 11c Busbar electrode 22 2nd IDT electrode 22A, 22B comb-shaped electrode 22a, 22b 2nd electrode finger 22c Busbar electrode 31 1st reflector 31a 1st reflective electrode finger 31c Busbar electrode 42 Second reflector 42a 2nd reflective electrode finger 42c Busbar electrode 50, 60 terminals 70 Common terminal 81, 82 input / output terminals 100 Piezoelectric layer 100a First main surface 100b Second main surface 110a, 110b electrode layer 113 First insulating layer 114 Second insulating layer 130A, 130B Via conductor 153 Low sound speed layer 155 High-sonic support substrate d1 1st direction d2 2nd direction d3 Third direction E End area m1 1st area m2 2nd area MR interreflector area p11, p12, p13, p14 Parallel arm resonators s11, s12, s13, s14, s15 series arm resonators

Claims

1. A piezoelectric layer; a first IDT electrode and a plurality of first reflectors formed on a first main surface of the piezoelectric layer; a second IDT electrode and a plurality of second reflectors formed on a second main surface of the piezoelectric layer opposite to the first main surface; Equipped with the first IDT electrode has a plurality of first electrode fingers arranged to extend in a second direction intersecting the first direction in a direction along the first principal surface, each of the first reflectors includes a plurality of first reflective electrode fingers arranged on both outer sides of the first IDT electrode in the first direction and extending in the second direction; the second IDT electrode has a plurality of second electrode fingers arranged to extend in the second direction intersecting the first direction in a direction along the second principal surface, each of the second reflectors is disposed on both outer sides of the second IDT electrode in the first direction and includes a plurality of second reflective electrode fingers disposed to extend in the second direction; A region between the plurality of first reflectors in the first direction is defined as a first region, A region between the plurality of second reflectors in the first direction is a second region, When a minimum area including the first area and the second area as viewed from a third direction perpendicular to both the first direction and the second direction is defined as an inter-reflector area, an end region in the first direction of the inter-reflector region has a region in which the first electrode finger and the second electrode finger do not face each other in the third direction; or The inter-reflector region has an end region in the first direction, in which the first reflective electrode finger and the second reflective electrode finger do not face each other in the third direction. Acoustic wave element.

2. a second insulating layer formed on the second main surface so as to cover the second electrode fingers and the second reflective electrode fingers; In a region on the second main surface that is located in the third direction as viewed from the first electrode fingers located in the end region, the second electrode fingers are not arranged and the second insulating layer is formed. The acoustic wave element according to claim 1 .

3. a first insulating layer formed on the first main surface so as to cover the first electrode fingers and the first reflective electrode fingers; In a region on the first main surface that is located in the third direction as viewed from the second electrode fingers located in the end region, the first electrode fingers are not arranged and the first insulating layer is formed. The acoustic wave element according to claim 1 .

4. a second insulating layer formed on the second main surface so as to cover the second electrode fingers and the second reflective electrode fingers; In a region on the second main surface that is located in the third direction as viewed from the first reflective electrode fingers located in the end region, the second reflective electrode fingers are not arranged and the second insulating layer is formed. The acoustic wave element according to claim 1 .

5. a first insulating layer formed on the first main surface so as to cover the first electrode fingers and the first reflective electrode fingers; In a region on the first main surface that is located in the third direction as viewed from the second reflective electrode fingers located in the end region, the first reflective electrode fingers are not arranged and the first insulating layer is formed. The acoustic wave element according to claim 1 .

6. an inter-reflector region having an end region in the first direction, the inter-reflector region having an area in which the first electrode finger and the second electrode finger do not face each other in the third direction, and the first reflective electrode finger and the second reflective electrode finger have an area in which the first reflective electrode finger and the second reflective electrode finger do not face each other in the third direction; The acoustic wave element according to claim 1 .

7. In a region on the second main surface that is located in the third direction as viewed from the first electrode fingers located in the end region, the second electrode fingers are not arranged, but the second reflective electrode fingers are arranged. The acoustic wave element according to claim 6 .

8. In a region on the first main surface that is located in the third direction as viewed from the second electrode fingers located in the end region, the first electrode fingers are not arranged, but the first reflective electrode fingers are arranged. The acoustic wave element according to claim 6 .

9. the end region has one end region and another end region in the first direction of the inter-reflector region, In the one end region and the other end region, the number of the first electrode fingers and the second electrode fingers that are not opposed to each other is within a range of more than 0% to 5% of the total number of the first electrode fingers and the first reflective electrode fingers or the total number of the second electrode fingers and the second reflective electrode fingers. The acoustic wave element according to any one of claims 1 to 8.

10. the end region has one end region and another end region in the first direction of the inter-reflector region, In the one end region and the other end region, the number of the first reflective electrode fingers and the second reflective electrode fingers that are not opposed to each other is within a range of more than 0% and not more than 5% of the total number of the first electrode fingers and the first reflective electrode fingers or the total number of the second electrode fingers and the second reflective electrode fingers. The acoustic wave element according to any one of claims 1 to 8.

11. moreover, a high acoustic velocity support substrate in which a bulk wave propagates at a higher acoustic velocity than an elastic wave propagates through the piezoelectric layer; a low acoustic velocity layer disposed between the high acoustic velocity support substrate and the piezoelectric layer, the low acoustic velocity layer having a bulk wave acoustic velocity slower than an elastic wave acoustic velocity propagating through the piezoelectric layer; Equipped with The low acoustic velocity layer is provided on the second main surface so as to cover the second IDT electrode and the second reflector. The acoustic wave element according to claim 1 .

12. The acoustic wave device according to any one of claims 1 to 8 is included. An elastic wave filter device.

13. a plurality of filters each including the acoustic wave filter device according to claim 12; an input / output terminal and one of the input / output terminals of each of the plurality of filters are directly or indirectly connected to a common terminal; At least one of the filters other than the acoustic wave filter device has a passband higher than the frequency of the passband of the acoustic wave filter device. Multiplexer.

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