Elastic wave resonator and elastic wave filter device

Abstract

To suppress an increase in the size of an unwanted wave in an elastic wave resonator.SOLUTION: An elastic wave resonator 10 includes a piezoelectric layer 100 and an IDT electrode 11. A plurality of electrode fingers 11a and 11b of the IDT electrode 11 are arranged in a first direction d1 along a main surface 100a of a piezoelectric layer 100. A region in which the IDT electrode 11 is formed has a plurality of divided regions D provided in a matrix along a first direction d1 and a second direction d2 in which the electrode fingers 11a and 11b extend. A divided region D is a region including a part of the number of electrode fingers among the plurality of electrode fingers 11a and 11b and a part of the electrode fingers in the longitudinal direction. The plurality of divided regions D include one divided region Ba and the other divided region Bb adjacent to each other in the second direction d2. The duty in one divided region Ba is larger than the duty in the other divided region Bb, and the electrode finger pitch in one divided region Ba is smaller than the electrode finger pitch in the other divided region Bb.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an acoustic wave resonator and an acoustic wave filter device having an acoustic wave resonator. [Background technology]

[0002] Conventionally, acoustic wave resonators equipped with IDT electrodes are known. Acoustic wave resonators generate various unwanted waves in addition to the main mode used to form the filter band. For example, unwanted waves occur outside the filter band as SH waves, Rayleigh waves, or higher-order mode waves. Unwanted waves also occur within the filter band as longitudinal or transverse mode waves. Wireless communication systems that communicate by bundling multiple frequency bands need to suppress these unwanted waves.

[0003] Patent Document 1 discloses an acoustic wave filter that suppresses Rayleigh wave spurious by adjusting the duty of the IDT electrodes over the entire length in the acoustic wave propagation direction. Patent Document 2 discloses an acoustic wave resonator that reduces the intensity of spurious while maintaining uniformity of the resonant frequency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 198904 [Patent Document 2] International Publication No. 2021 / 177108 Summary of the Invention [Problem to be solved by the invention]

[0005] The elastic wave resonator described in Patent Document 1 can suppress unwanted Rayleigh waves, but has the problem of a decrease in the impedance ratio of the main response.The elastic wave resonator described in Patent Document 2 can suppress unwanted Rayleigh waves and prevent a decrease in the impedance ratio of the main response, but still has the problem of insufficient suppression of unwanted waves.

[0006] The present invention provides an elastic wave resonator and the like that can suppress the increase of unwanted waves. [Means for solving the problem]

[0007] An elastic wave resonator according to one aspect of the present invention comprises a piezoelectric layer and an IDT electrode formed on a main surface of the piezoelectric layer, the IDT electrode having a plurality of electrode fingers arranged in a first direction along the main surface of the piezoelectric layer, the plurality of electrode fingers being arranged in a matrix along the first direction and a second direction in which the electrode fingers extend, the plurality of divided regions being regions including a portion of the plurality of electrode fingers and a portion of the longitudinal direction of the electrode fingers, the plurality of divided regions including one divided region and another divided region adjacent to each other in the second direction, the duty in the one divided region being larger than the duty in the other divided region, and the electrode finger pitch in the one divided region being smaller than the electrode finger pitch in the other divided region.

[0008] An acoustic wave filter device according to one aspect of the present invention is an acoustic wave filter device including the above-described acoustic wave resonator. [Effects of the Invention]

[0009] According to the elastic wave resonator and the like according to the present invention, it is possible to suppress unwanted waves from increasing in size. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are a plan view and a cross-sectional view schematically illustrating an electrode configuration of an elastic wave resonator according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a first group of divided regions, a second group of divided regions, and divided regions in a region where an IDT electrode is formed. [Figure 3] FIG. 10 is a diagram showing the duty of an IDT electrode. [Figure 4] FIG. 2 is a diagram showing the electrode finger pitch of an IDT electrode. [Figure 5] FIG. 10 is a diagram illustrating a schematic diagram showing differences in duties among a plurality of divided regions. [Figure 6A] FIG. 10 is a diagram showing changes in the duty of a divided region in a predetermined second divided region group. [Figure 6B] FIG. 10 is a diagram showing changes in the duties of divided regions in a plurality of second divided region groups. [Figure 7A] FIG. 2 is a diagram schematically illustrating an IDT electrode of the acoustic wave resonator according to the first embodiment. [Figure 7B] 2 is an enlarged view of a portion of an IDT electrode of the acoustic wave resonator according to the first embodiment. FIG. [Figure 8] FIG. 10 is a diagram showing specific examples of duties of a plurality of divided regions. [Figure 9] FIG. 10 is a diagram showing the correspondence relationship between duty and electrode finger pitch. [Figure 10] FIG. 10 is a diagram illustrating the relationship between duty and wavelength in a divided region. [Figure 11] 1 is a diagram schematically illustrating a cross section of an elastic wave resonator according to a first embodiment. [Figure 12] 10A and 10B are diagrams illustrating IDT electrodes of an acoustic wave resonator according to Comparative Example 1. [Figure 13] FIG. 3 is a diagram showing impedance characteristics of elastic wave resonators according to Example 1 and Comparative Example 1. [Figure 14] FIG. 3 is a diagram illustrating the return losses of the acoustic wave resonators of Example 1 and Comparative Example 1. [Figure 15] FIG. 3 is a diagram showing impedance phase characteristics of elastic wave resonators according to Example 1 and Comparative Example 1. [Figure 16] 10A and 10B are diagrams illustrating an example of an IDT electrode of an acoustic wave resonator according to a second embodiment. [Figure 17A]FIG. 10 is a diagram showing changes in the duty of a predetermined second divided region group in the second embodiment. [Figure 17B] FIG. 10 is a diagram showing changes in the duties of divided regions in a plurality of second divided region groups in the second embodiment. [Figure 18] FIG. 10 is a diagram illustrating another example of an IDT electrode of the acoustic wave resonator according to the second embodiment. [Figure 19] FIG. 10 is a diagram showing impedance characteristics of elastic wave resonators according to Example 2 and Comparative Example 1. [Figure 20] FIG. 10 is a diagram illustrating the return losses of the acoustic wave resonators of Example 2 and Comparative Example 1. [Figure 21] FIG. 10 is a diagram showing impedance phase characteristics of elastic wave resonators according to Example 2 and Comparative Example 1. [Figure 22A] FIG. 11 is a diagram showing changes in the duty of a predetermined second divided region group in the third embodiment. [Figure 22B] FIG. 11 is a diagram showing changes in the duties of divided regions in a plurality of second divided region groups according to the third embodiment. [Figure 23A] FIG. 13 is a diagram showing changes in the duty of a predetermined second divided region group in the fourth embodiment. [Figure 23B] FIG. 13 is a diagram showing changes in the duties of divided regions in a plurality of second divided region groups according to the fourth embodiment. [Figure 24A] FIG. 13 is a diagram showing changes in the duty of a predetermined second divided region group in the fifth embodiment. [Figure 24B] FIG. 13 is a diagram showing changes in the duties of the divided regions in a plurality of second divided region groups according to the fifth embodiment. [Figure 25A] FIG. 20 is a diagram showing changes in the duty of a predetermined second divided region group in the sixth embodiment. [Figure 25B] FIG. 20 is a diagram showing changes in the duties of the divided regions in a plurality of second divided region groups according to the sixth embodiment. [Figure 26A] FIG. 20 is a diagram showing changes in the duty of a predetermined second divided region group in the seventh embodiment. [Figure 26B]FIG. 20 is a diagram showing changes in the duties of the divided regions in a plurality of second divided region groups according to the seventh embodiment. [Figure 27] FIG. 2 is a diagram illustrating impedance phase characteristics of elastic wave resonators according to first, second, and third examples. [Figure 28] FIG. 2 is a diagram illustrating impedance phase characteristics of elastic wave resonators according to Examples 1, 5, and 6. [Figure 29] FIG. 1 is a diagram showing the maximum values ​​of unwanted responses of Rayleigh waves in Examples 1, 2, 3, 5, and 6 and Comparative Example 1. [Figure 30] 13 is a diagram illustrating an example of an IDT electrode of an acoustic wave resonator according to an eighth embodiment. FIG. [Figure 31] FIG. 13 is a diagram illustrating another example of an IDT electrode of the acoustic wave resonator according to the eighth embodiment. [Figure 32] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 33] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 34] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 35] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 36] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 37] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 38] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 39] FIG. 10 is a diagram illustrating another example of a cross section of an elastic wave resonator. [Figure 40] FIG. 10 is a diagram illustrating a circuit configuration of an acoustic wave filter device according to a second embodiment. [Figure 41] FIG. 10 is a diagram showing a circuit configuration of a multiplexer and its peripheral circuits according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail using diagrams and tables. Note that the examples described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangements, and connection forms 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 recited in the independent claims are described as optional components. Furthermore, the sizes or size ratios of the components shown in the drawings are not necessarily strict.

[0012] (Embodiment 1) [Basic structure of an elastic wave resonator] The basic configuration of an elastic wave resonator according to a first embodiment will be described with reference to FIG.

[0013] FIG. 1 is a plan view and a cross-sectional view schematically illustrating an electrode configuration of an acoustic wave resonator 10 according to a first embodiment.

[0014] The elastic wave resonator 10 shown in the figure is formed of a piezoelectric layer 100, an electrode 110, and a protective film 113, and includes an IDT (InterDigital Transducer) electrode 11 configured from these components, and a plurality of reflectors 12. The elastic wave resonator 10 according to this embodiment is a surface acoustic wave (SAW) resonator configured from the IDT electrode 11, the plurality of reflectors 12, and the piezoelectric layer 100.

[0015] 1 is shown for the purpose of illustrating a typical structure of the acoustic wave resonator 10, and the number and length of the electrode fingers constituting the electrodes are not limited to this. The piezoelectric layer 100 may be a piezoelectric substrate.

[0016] The electrode 110 constituting the IDT electrode 11 and the plurality of reflectors 12 has a laminated structure of an adhesive layer 111 and a main electrode layer 112, as shown in the cross-sectional view of FIG.

[0017] The adhesive layer 111 is a layer for improving the adhesiveness between the piezoelectric layer 100 and the main electrode layer 112, and is made of, for example, Ti.

[0018] The main electrode layer 112 is made of, for example, Al. The main electrode layer 112 may contain Cu in addition to Al.

[0019] The protective film 113 is formed to cover the electrode 110. The protective film 113 is a layer intended to protect the main electrode layer 112 from the external environment, adjust the frequency-temperature characteristics, and increase moisture resistance, and is, for example, a film whose main component is silicon dioxide (SiO2).

[0020] The materials constituting the adhesion layer 111, the main electrode layer 112, and the protective film 113 are not limited to those mentioned above. Furthermore, the electrode 110 does not have to have the above-mentioned laminated structure. The electrode 110 may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a laminate of multiple layers made of the above-mentioned metals or alloys. Furthermore, the protective film 113 does not have to be formed.

[0021] As shown in the plan view of FIG. 1, the IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B facing each other.

[0022] Here, a predetermined direction along the main surface 100a of the piezoelectric layer 100 is referred to as a first direction d1, and a direction along the main surface 100a of the piezoelectric layer 100 and intersecting the first direction d1 is referred to as a second direction d2. The first direction d1 is the propagation direction of an elastic wave in the elastic wave resonator 10. In this embodiment, the first direction d1 and the second direction d2 are perpendicular to each other.

[0023] The interdigital electrode 11A is composed of a plurality of electrode fingers 11a arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the electrode fingers 11a to each other. The interdigital electrode 11B is composed of a plurality of electrode fingers 11b arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the electrode fingers 11b to each other. The electrode fingers 11a and 11b are arranged alternately along the first direction d1.

[0024] The reflector 12 is arranged next to the IDT electrode 11 in the first direction d1. The multiple reflectors 12 are arranged on both outer sides of the IDT electrode 11. The multiple reflectors 12 are composed of one reflector 12 located on the negative side of the IDT electrode 11 in the first direction d1 and the other reflector 12 located on the positive side of the first direction d1 when viewed from the IDT electrode 11. The reflector 12 is composed of multiple reflective electrode fingers 12a arranged to extend in the second direction d2 and a bus bar electrode 12c connecting one ends of the multiple reflective electrode fingers 12a to each other.

[0025] [Detailed configuration of elastic wave resonator] The detailed configuration of acoustic wave resonator 10 will be described with reference to FIGS. 2 to 6B.

[0026] FIG. 2 is a diagram showing a first group of divided regions, a second group of divided regions, and divided regions in the region where the IDT electrode 11 is formed.

[0027] FIG. 2 shows a plurality of first divided area groups A1, A2, A3, A4, A5, A6 and A7, a plurality of second divided area groups B1, B2, B3, B4, B5, B6 and B7, and a plurality of divided areas D.

[0028] The first divided region groups A1 to A7 are vertically long rectangular regions surrounded by dashed lines in FIG. 2. The first divided region groups A1 to A7 are arranged along the first direction d1 in a region on the main surface 100a of the piezoelectric layer 100 where the IDT electrode 11 is formed. Each of the first divided region groups A1 to A7 is formed by a region including one or more electrode fingers 11a (or 11b). In this example, each of the first divided region groups A1 to A7 is formed by a region including three electrode fingers. Each of the first divided region groups A1 to A7 is formed so as to include the entire longitudinal length of the electrode fingers extending in the second direction d2. The first divided region groups A1 to A7 all have the same length in the first direction d1 and the same length in the second direction d2.

[0029] The second divided region groups B1 to B7 are horizontally long rectangular regions surrounded by dashed lines in FIG. 2. The second divided region groups B1 to B7 are arranged in the region where the IDT electrode 11 is formed, along the second direction d2. Specifically, the second divided region groups B1 to B7 are formed in an intersection region T1 where the electrode fingers 11a and 11b intersect within the region where the IDT electrode 11 is formed. The intersection region T1 is a region where the electrode fingers 11a and 11b overlap when the IDT electrode 11 is viewed from the first direction d1. Each of the second divided region groups B1 to B7 intersects with the electrode fingers 11a and 11b. In this example, each of the second divided region groups B1 to B7 is formed to span 21 electrode fingers 11a and 11b. The plurality of second divided region groups B1 to B7 all have the same length in the second direction d2, and the same length in the first direction d1.

[0030] Although the above example shows that the number of divisions in each of the first and second divided area groups is seven, the number of divisions in each of the first and second divided area groups may be two or more.

[0031] The multiple divided regions are regions separated by dashed lines in Fig. 2. The multiple divided regions D are arranged in a matrix along the first direction d1 and the second direction d2 in the region where the IDT electrode 11 is formed. The multiple divided regions D are regions defined by multiple first divided region groups A1 to A7 and multiple second divided region groups B1 to B7, and are formed in a matrix by being partitioned by the first divided region groups A1 to A7 and the second divided region groups B1 to B7. In this example, the multiple divided regions D are configured by 7 in the first direction d1 and 7 in the second direction d2, for a total of 49 divided regions.

[0032] Each divided region D is a region that includes a portion of the electrode fingers 11a, 11b and a portion of the electrode fingers in the longitudinal direction. In this example, each divided region D is a region that includes three electrode fingers and 1 / 7 of the length of the electrode fingers in the longitudinal direction. The lengths of the divided regions D in the first direction d1 are all the same, and the lengths of the divided regions D in the second direction d2 are all the same.

[0033] The electrode duty and electrode finger pitch are constant in each of the plurality of divided regions D. Here, the duty and electrode finger pitch of the IDT electrode 11 will be described.

[0034] FIG. 3 is a diagram showing the duty of the IDT electrode 11. As shown in FIG.

[0035] The duty is the ratio of the area occupied by the electrode to the unit area. The duty is set in advance for the electrode fingers in each divided area D. For example, the duty is set for each divided area D so that it takes on different values ​​within a predetermined range with 0.5 as the base. The duty is actually derived as follows. For example, when multiple electrode fingers 11a, 11b are arranged in the first direction d1, the duty in the divided area D is derived by using the width w of the electrode fingers as the numerator and the sum of the width w of the electrode fingers and the width s of the gap areas where no electrode fingers are present as the denominator (duty = w / (w + s)).

[0036] FIG. 4 is a diagram showing the electrode finger pitch of the IDT electrode 11. As shown in FIG.

[0037] The electrode finger pitch is the arrangement pitch of the multiple electrode fingers 11a, 11b arranged in the first direction d1. The electrode finger pitch is set in advance corresponding to the above-mentioned duty. In the example shown in FIG. 4, the electrode finger pitch in the divided region D of the first divided region group A1 is p1, and the electrode finger pitch in the divided region D of the first divided region group A2 is p2. The electrode finger pitch is actually derived as follows. For example, when the multiple electrode fingers 11a, 11b are arranged in the first direction d1, the electrode finger pitch in the divided region D is derived by dividing the distance in the first direction d1 between the electrode fingers at both ends of the divided region D by (the number of electrode fingers in the divided region D)−1.

[0038] FIG. 5 is a diagram showing a schematic diagram of differences in duties among a plurality of divided regions D. In FIG.

[0039] In Fig. 5, multiple patterns of divided regions D with different duties are shown by applying different hatching to electrode fingers 11a and 11b. In this example, seven patterns of divided regions D defined by seven patterns of duties are shown. The electrode finger pitch is determined so as to correspond to the seven patterns of duties. As shown in Fig. 5, the multiple divided regions D are formed so that the duties change continuously in the first direction d1 and the second direction d2.

[0040] Fig. 6A is a diagram showing changes in the duty of divided regions D in a predetermined second divided region group, and Fig. 6B is a diagram showing changes in the duty of divided regions D in a plurality of second divided region groups B1 to B7.

[0041] These figures show coordinates in which the first axis represents the array number of the electrode fingers 11a, 11b arranged in order in the first direction d1, and the second axis represents the duty. Specifically, the second axis is a function related to the weight of the duty.

[0042] FIG. 6A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in FIG. 6A, the divided region D is formed so that the duty of the divided region D describes a step-like waveform at this coordinate. FIG. 6B shows how the duty of the divided regions D located in multiple second divided region groups B1 to B7 changes depending on the coordinate position on the first axis. As shown in FIG. 6B, the multiple divided regions D are formed so that the duties of each of the multiple divided regions D describe multiple waveforms with the same shape but different phases at this coordinate. Note that although the duty changes upward to the right in FIGS. 6A and 6B, this is not limiting and the duty may change downward to the right.

[0043] 5, each of the first divided region groups A1 to A7 includes one divided region Ba and another divided region Bb adjacent to each other in the second direction d2. In this embodiment, the duty in the one divided region Ba is larger than the duty in the other divided region Bb, and the electrode finger pitch in the one divided region Ba is smaller than the electrode finger pitch in the other divided region Bb.

[0044] For example, if one divided region Ba is a divided region D of the second divided region group B1 (hereinafter referred to as B1) and the other divided region Bb is a divided region D of the second divided region group B2 (hereinafter referred to as B2), the duty in the divided region D of B1 is greater than the duty in the divided region of B2, and the electrode finger pitch in the divided region D of B1 is smaller than the electrode finger pitch in the divided region D of B2. Note that this magnitude relationship may be reversed. In other words, if one divided region Ba is the divided region D of B2 and the other divided region Bb is the divided region D of B1, the duty in the divided region D of B2 may be greater than the duty in the divided region of B1, and the electrode finger pitch in the divided region D of B2 may be smaller than the electrode finger pitch in the divided region D of B1. These relationships are similar for the other second divided region groups B2 to B7.

[0045] 5, each of the second divided region groups B1 to B7 includes one divided region Aa and another divided region Ab adjacent to each other in the first direction d1. In this embodiment, the duty in one divided region Aa is larger than the duty in the other divided region Ab, and the electrode finger pitch in one divided region Aa is smaller than the electrode finger pitch in the other divided region Ab.

[0046] For example, if one divided region Aa is the divided region D of the first divided region group A1 (hereinafter referred to as A1) and the other divided region Ab is the divided region D of the first divided region group A2 (hereinafter referred to as A2), the duty in the divided region D of A1 is greater than the duty in the divided region A2, and the electrode finger pitch in the divided region D of A1 is smaller than the electrode finger pitch in the divided region D of A2. Note that this magnitude relationship may be reversed. In other words, if one divided region Aa is the divided region D of A2 and the other divided region Ab is the divided region D of A1, the duty in the divided region D of A2 may be greater than the duty in the divided region A1, and the electrode finger pitch in the divided region D of A2 may be smaller than the electrode finger pitch in the divided region D of A1. These relationships are similar for the other first divided region groups A2 to A7.

[0047] In this embodiment, in one divided region Aa and the other divided region Ab adjacent to each other in the first direction d1, the resonance frequency determined based on the duty and electrode finger pitch of one divided region Aa and the resonance frequency determined based on the duty and electrode finger pitch of the other divided region Ab are formed to match each other. Also, in one divided region Ba and the other divided region Bb adjacent to each other in the second direction d2, the resonance frequency determined based on the duty and electrode finger pitch of one divided region Ba and the resonance frequency determined based on the duty and electrode finger pitch of the other divided region Bb are formed to match each other.

[0048] In other words, the elastic wave resonator 10 has a configuration in which the duty and electrode finger pitch are different between adjacent divided areas D in the first direction d1, the duty and electrode finger pitch are different between adjacent divided areas D in the second direction d2, and the resonant frequencies of these adjacent divided areas D are the same.

[0049] In this way, by making the duties different between adjacent divided regions D, it is possible to appropriately distribute the frequencies of unwanted waves such as longitudinal modes and Rayleigh waves. This makes it possible to prevent unwanted waves from becoming large. Furthermore, by matching the resonant frequencies of the main modes, it is possible to prevent a decrease in the impedance ratio and suppress deterioration of the main mode characteristics.

[0050] [Elastic wave resonator according to example 1] Elastic wave resonator 10 according to Example 1, which is one of examples of the first embodiment, will be described with reference to FIGS. 7A to 15. FIG.

[0051] Fig. 7A is a diagram schematically illustrating an IDT electrode 11 of an acoustic wave resonator 10 according to Example 1. Fig. 7B is an enlarged view of a portion of the IDT electrode 11 of the acoustic wave resonator 10 according to Example 1.

[0052] As shown in Fig. 7A, acoustic wave resonator 10 has an IDT electrode 11 and multiple reflectors 12. Fig. 7A is a schematic diagram, and the number of pairs of electrode fingers actually varies. For example, the number of pairs of electrode fingers 11a, 11b of IDT electrode 11 is 158, and the number of pairs of reflecting electrode fingers 12a of reflector 12 is 10.

[0053] 7A, the IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B. Each of the pair of comb-shaped electrodes 11A and 11B has a plurality of electrode fingers 11a and 11b, and a first bus bar electrode 31 connecting one end of each of the plurality of electrode fingers 11a and 11b.

[0054] As described above, the duty and electrode finger pitch patterns in the multiple divided regions D are different from one another, and therefore, as shown in Fig. 7B, the electrode fingers 11a, 11b are formed to have a stepped shape. At the boundary between adjacent divided regions D in the second direction d2, the electrode fingers are formed offset in the first direction d1 so that the positions of the center lines c1 of the electrode finger widths are different. The offset in the first direction d1 between two electrode fingers contacting at the boundary between the divided regions D is smaller than the width of the electrode fingers.

[0055] 7A, each of the pair of comb-shaped electrodes 11A, 11B has a second busbar electrode 32 that is thinner than the first busbar electrode 31. As shown in Fig. 7B, a high acoustic velocity portion 39 is formed between the first busbar electrode 31 and the second busbar electrode 32. In other words, the high acoustic velocity portion 39 is provided between both end portions 36 of the electrode fingers 11a, 11b and the first busbar electrode 31.

[0056] The second busbar electrode 32 is disposed between the first busbar electrode 31 and the plurality of divided regions D and parallel to the first busbar electrode 31. The plurality of divided regions D are regions that coincide with the intersection regions T1 where the plurality of electrode fingers 11a, 11b intersect. The intersection width of the electrode fingers 11a, 11b of the IDT electrode 11 is, for example, 11.62λ. Here, λ is a reference wavelength, and in this example, λ=1.98030 μm. A gap is formed between the tip of the electrode finger 11a (or 11b) and the second busbar electrode 32. The gap between the tip of the electrode fingers 11a, 11b and the second busbar electrode 32 is, for example, 0.135λ.

[0057] In this example, a second busbar electrode 34 that is thinner than the busbar electrode 12c is also formed on the reflector 12. The second busbar electrode 34 of the reflector 12 is provided at the same position as the second busbar electrode 32 in the second direction d2.

[0058] 7A and 7B, the IDT electrode 11 has piston mode forming regions 35 located at both end portions 36 of the electrode fingers 11a and 11b. The piston mode forming regions 35 are formed at both end portions 36 different from the central portions 37 (see FIG. 7B) of the electrode fingers 11a and 11b. The piston mode forming regions 35 are included in the divided regions D located at both ends in the second direction d2, among the plurality of divided regions D.

[0059] As shown in these figures, a load film 38 is formed on each of both end portions 36 of the electrode fingers 11a and 11b, thereby applying a piston mode to the IDT electrode 11. The load film 38 is a film that weights the electrode fingers 11a and 11b and is formed, for example, of an electrode film or an insulating film. The load film 38 is formed in a line parallel to the second busbar electrode 32 and is formed at the end of the intersection region T1 located closer to the center than the second busbar electrode 32. Note that the piston mode forming region 35 is not limited to the load film 38 and may be formed by a wide electrode portion that is wider than the width of the electrode fingers 11a and 11b. This wide electrode portion may be rectangular, T-shaped, plus (+)-shaped, or convex. Note that in this example, the reflector 12 also has a piston mode forming region 35. The piston mode forming region 35 of the reflector 12 is provided at the same position as the piston mode forming region 35 of the IDT electrode 11 in the second direction d2.

[0060] FIG. 8 is a diagram showing a specific example of the duties of a plurality of divided regions D.

[0061] FIG. 8 shows the respective duties of the plurality of divided regions D defined by the plurality of first divided region groups A1 to A7 and the plurality of second divided region groups B1 to B7. FIG. 8 also shows the duty of the reflector 12. In this example, the duty is set to 0.5 as a reference and the duty is changed so that the variation falls within a range of ±0.03. As shown in the table in FIG. 8, the plurality of divided regions D are formed so that the predetermined duty changes by continuously moving linearly in the first direction d1 and the second direction d2. In this example, the predetermined duty is set to move diagonally downward to the right.

[0062] For example, the duties of the multiple divided regions D shown in Fig. 8 are created by creating a standard model with the same duty (e.g., 0.5) and the same electrode finger pitch (e.g., 1.9803 µm), assigning different duties to each divided region D of a predetermined second divided region group (e.g., B1) of the standard model, and then assigning different duties to each divided region D of the multiple first divided region groups A1 to A7 based on the duty of the divided region D. The different duties are assigned with a predetermined regularity. The electrode finger pitch is set to be different for each divided region D corresponding to the duty.

[0063] FIG. 9 is a diagram showing the correspondence relationship between the duty and the electrode finger pitch.

[0064] Fig. 9 shows the electrode finger pitch and pitch ratio corresponding to the duty in Fig. 8. The pitch ratio is expressed as a ratio when the electrode finger pitch (=1.9803) when the duty is 0.5 is used as a reference. As shown in Fig. 9, the electrode finger pitch is set in accordance with changes in the duty. The duty and electrode finger pitch in this embodiment are set so that the resonance frequencies of the divided regions D are approximately the same.

[0065] FIG. 10 is a diagram showing the relationship between duty and wavelength in divided region D.

[0066] The horizontal axis of the figure shows the duty, and the vertical axis shows the wavelength and resonant frequency. The wavelength is twice the electrode finger pitch. Since the reciprocal of the wavelength is proportional to the frequency, changes in wavelength can be seen to indicate changes in frequency. As shown in Figure 10, by changing the electrode finger pitch in accordance with changes in duty, the resonant frequencies in each divided region D are made to be approximately the same.

[0067] In this specification, "one frequency and another frequency are substantially the same" means that the absolute value of the difference between the two frequencies is 10% or less. The absolute value of the difference between the frequencies is preferably 2% or less, and more preferably 1% or less.

[0068] FIG. 11 is a diagram schematically illustrating a cross section of an acoustic wave resonator 10 according to a first preferred embodiment.

[0069] 11 , the acoustic wave resonator 10 includes an IDT electrode 11, a piezoelectric layer 100, a low acoustic velocity layer 120, a high acoustic velocity layer 130, and a support substrate 150. The low acoustic velocity layer 120 and the high acoustic velocity layer 130 are intermediate layers 140 located between the piezoelectric layer 100 and the support substrate 150.

[0070] For example, the IDT electrode 11 is formed of a material containing Al. The thickness of the IDT electrode 11 is 100 nm (=0.05λ). The piezoelectric layer 100 is formed of LT (lithium tantalate single crystal or ceramics). For example, the piezoelectric layer 100 is "rotated Y-cut 55Y-X LT." The low acoustic velocity layer 120 is formed of SiO2, the high acoustic velocity layer 130 is formed of SiN, and the support substrate 150 is formed of Si(111)ψ73°. In other words, the acoustic wave resonator 10 of Example 1 has a layered structure represented by "LT / SiO2 / SiN / Si(111)ψ73°." The thicknesses of LT / SiO2 / SiN / Si are 0.2λ / 0.15λ / 0.15λ, respectively.

[0071] The effects of acoustic wave resonator 10 of Example 1 having the above configuration will be described while comparing Example 1 with Comparative Example 1.

[0072] FIG. 12 is a diagram showing an IDT electrode 511 of an acoustic wave resonator 510 of the first comparative example.

[0073] Acoustic wave resonator 510 of Comparative Example 1 has IDT electrode 511 and a plurality of reflectors 12. The number of pairs of IDT electrode 511 and reflectors 12 is the same as in Example 1. The overlap width of electrode fingers 11a and 11b of IDT electrode 511 is the same as in Example 1.

[0074] The IDT electrode 511 has a pair of comb-shaped electrodes 11A and 11B. Each of the pair of comb-shaped electrodes 11A and 11B has a plurality of electrode fingers 11a and 11b, a first busbar electrode 31 connecting one ends of the plurality of electrode fingers 11a and 11b, and a second busbar electrode 32 that is thinner than the first busbar electrode 31. The gap between the tips of the electrode fingers 11a and 11b and the second busbar electrode 32 is the same as in Example 1. Furthermore, the IDT electrode 511 and the reflector 12 have a piston mode forming region 35, similar to Example 1.

[0075] In acoustic wave resonator 510 of Comparative Example 1, the duties in the plurality of divided regions D are all the same, that is, 0.5. In addition, in acoustic wave resonator 510 of Comparative Example 1, the electrode finger pitches in the plurality of divided regions D are all the same.

[0076] FIG. 13 is a diagram illustrating impedance characteristics of the elastic wave resonators of Example 1 and Comparative Example 1. In FIG.

[0077] The impedance characteristics of the main mode of the elastic wave resonator are shown in Fig. 13. As shown in Fig. 13, elastic wave resonator 10 of Example 1 has an impedance ratio equivalent to that of elastic wave resonator 510 of Comparative Example 1. In other words, the characteristics of the main mode are maintained in elastic wave resonator 10 of Example 1.

[0078] FIG. 14 is a diagram illustrating the return losses of the acoustic wave resonators of Example 1 and Comparative Example 1. In FIG.

[0079] 14 shows the return loss of the main mode of the acoustic wave resonator. As shown in FIG. 14, acoustic wave resonator 10 of Example 1 has suppressed responses in the longitudinal mode and the transverse mode compared to acoustic wave resonator 510 of Comparative Example 1.

[0080] FIG. 15 is a diagram illustrating impedance phase characteristics of the elastic wave resonators of Example 1 and Comparative Example 1. In FIG.

[0081] The response of Rayleigh waves occurring outside the band is shown in Fig. 15. As shown in Fig. 15, the response of Rayleigh waves in elastic wave resonator 10 of Example 1 is suppressed compared to elastic wave resonator 510 of Comparative Example 1.

[0082] As described above, acoustic wave resonator 10 according to the first embodiment can suppress unwanted waves more effectively than comparative example 1.

[0083] [Elastic wave resonator according to the second embodiment] Elastic wave resonator 10 according to Example 2, which is one of examples of Embodiment 1, will be described with reference to Fig. 16 to Fig. 21. Example 2 describes an example in which the first divided region group is configured by a region including only one electrode finger.

[0084] FIG. 16 is a diagram illustrating an example of an IDT electrode 11 of an acoustic wave resonator 10 according to a second embodiment.

[0085] Acoustic wave resonator 10 includes IDT electrode 11 and a plurality of reflectors 12. IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B that face each other.

[0086] The interdigital electrode 11A is composed of a plurality of electrode fingers 11a arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the electrode fingers 11a to each other. The interdigital electrode 11B is composed of a plurality of electrode fingers 11b arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the electrode fingers 11b to each other. The electrode fingers 11a and 11b are arranged alternately along the first direction d1.

[0087] The reflector 12 is arranged next to the IDT electrode 11 in the first direction d1. The multiple reflectors 12 are arranged on both outer sides of the IDT electrode 11. The reflector 12 is composed of multiple reflective electrode fingers 12a arranged to extend in the second direction d2 and busbar electrodes 12c connecting one ends of the multiple reflective electrode fingers 12a to each other.

[0088] In the region where the IDT electrodes 11 are formed, a plurality of first divided region groups A1 to A21, a plurality of second divided region groups B1 to B7, and a plurality of divided regions D are formed.

[0089] The multiple first divided region groups A1 to A21 are formed to line up along the first direction d1 in a region on the main surface 100a of the piezoelectric layer 100 where the IDT electrode 11 is formed. Each of the multiple first divided region groups A1 to A21 is formed by a region including one electrode finger 11a (or 11b). Each of the first divided region groups A1 to A21 is formed to include the entire longitudinal length of the electrode finger extending in the second direction d2. The multiple first divided region groups A1 to A21 all have the same length in the first direction d1 and the same length in the second direction d2.

[0090] The second divided region groups B1 to B7 are arranged side by side in the second direction d2 in the region where the IDT electrode 11 is formed. Specifically, the second divided region groups B1 to B7 are formed in an intersection region T1 where the electrode fingers 11a, 11b intersect within the region where the IDT electrode 11 is formed. Each of the second divided region groups B1 to B7 intersects with the electrode fingers 11a, 11b. In this example, each of the second divided region groups B1 to B7 is formed across 21 of the electrode fingers 11a, 11b. The second divided region groups B1 to B7 all have the same length in the second direction d2 and the same length in the first direction d1.

[0091] The plurality of divided regions D are arranged in a matrix along the first direction d1 and the second direction d2 in the region where the IDT electrode 11 is formed. The plurality of divided regions D are regions defined by a plurality of first divided region groups A1 to A21 and a plurality of second divided region groups B1 to B7, and are formed in a matrix by being partitioned by the first divided region groups A1 to A21 and the second divided region groups B1 to B7. In this example, the plurality of divided regions D are configured by 21 in the first direction d1 and 7 in the second direction d2, for a total of 147 divided regions.

[0092] Each divided region D is a region that includes a portion of the multiple electrode fingers 11a, 11b and a portion of the electrode fingers in the longitudinal direction. In this example, each divided region D is a region that includes one electrode finger and 1 / 7 of the length of the electrode finger in the longitudinal direction. The multiple divided regions D all have the same length in the first direction d1, and the multiple divided regions D all have the same length in the second direction d2. Within each of the multiple divided regions D, the electrode duty is constant. The pitch of the electrode fingers within the divided region D is constant.

[0093] 17A is a diagram showing changes in duty of divided region D in a predetermined second divided region group in Example 2. FIG. 17B is a diagram showing changes in duty of divided region D in a plurality of second divided region groups B1 to B7 in Example 2.

[0094] These figures show coordinates in which the first axis represents the array number of the electrode fingers 11a, 11b arranged in order in the first direction d1, and the second axis represents the duty. Specifically, the second axis is a function related to the weight of the duty.

[0095] 17A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in FIG. 17A, the divided region D is formed so that the duty of the divided region D describes a triangular waveform at this coordinate. FIG. 17B shows how the duty of each divided region D located in the multiple second divided region groups B1 to B7 changes depending on the coordinate position on the first axis. As shown in FIG. 17B, the multiple divided regions D are formed so that the duties of each divided region D describe multiple waveforms with the same shape but different phases at this coordinate.

[0096] 16, each of the first divided region groups A1 to A21 includes one divided region Ba and another divided region Bb adjacent to each other in the second direction d2. In this embodiment, the duty in the one divided region Ba is larger than the duty in the other divided region Bb, and the electrode finger pitch in the one divided region Ba is smaller than the electrode finger pitch in the other divided region Bb.

[0097] 16, each of the second divided region groups B1 to B7 includes one divided region Aa and another divided region Ab adjacent to each other in the first direction d1. In this embodiment, the duty in one divided region Aa is larger than the duty in the other divided region Ab, and the electrode finger pitch in one divided region Aa is smaller than the electrode finger pitch in the other divided region Ab.

[0098] In this embodiment, in one divided region Aa and the other divided region Ab adjacent to each other in the first direction d1, the resonance frequency determined based on the duty and electrode finger pitch of one divided region Aa and the resonance frequency determined based on the duty and electrode finger pitch of the other divided region Ab are formed to match each other. Also, in one divided region Ba and the other divided region Bb adjacent to each other in the second direction d2, the resonance frequency determined based on the duty and electrode finger pitch of one divided region Ba and the resonance frequency determined based on the duty and electrode finger pitch of the other divided region Bb are formed to match each other.

[0099] In other words, the elastic wave resonator 10 of Example 2 has a configuration in which the duty and electrode finger pitch are different between adjacent divided areas D in the first direction d1, the duty and electrode finger pitch are different between adjacent divided areas D in the second direction d2, and the resonant frequencies of these adjacent divided areas are the same.

[0100] In this way, by making the duties different between adjacent divided regions D, it is possible to appropriately distribute the frequencies of unwanted waves such as longitudinal modes and Rayleigh waves. This makes it possible to prevent unwanted waves from becoming large. Furthermore, by matching the resonant frequencies of the main modes, it is possible to prevent a decrease in the impedance ratio and suppress deterioration of the main mode characteristics.

[0101] FIG. 18 is a diagram illustrating another example of the IDT electrode 11 of the acoustic wave resonator 10 according to the second embodiment.

[0102] An acoustic wave resonator 10 according to the second embodiment includes an IDT electrode 11 and a plurality of reflectors 12. Fig. 18 is a schematic diagram, and the number of pairs of electrode fingers is different in practice. For example, the number of pairs of electrode fingers 11a, 11b of the IDT electrode 11 is 158, and the number of pairs of reflecting electrode fingers 12a of the reflector 12 is 10.

[0103] 18, the IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B. Each of the pair of comb-shaped electrodes 11A and 11B has a plurality of electrode fingers 11a and 11b, and a first bus bar electrode 31 connecting one end of each of the plurality of electrode fingers 11a and 11b. The duty and electrode finger pitch patterns in the plurality of divided regions D are different from each other.

[0104] 18, each of the pair of comb-shaped electrodes 11A and 11B has a second busbar electrode 32 that is thinner than the first busbar electrode 31. In this example, the reflector 12 also has a second busbar electrode 34 that is thinner than the busbar electrode 12c. The IDT electrode 11 also has piston mode forming regions 35 located at both end portions 36 of the electrode fingers 11a and 11b.

[0105] The effects of elastic wave resonator 10 of Example 2 having the above configuration will be described by comparing Example 2 with Comparative Example 1. The elastic wave resonator used to confirm the effects is elastic wave resonator 10 shown in FIG. 18. Elastic wave resonator 510 of Comparative Example 1 has the configuration described above.

[0106] FIG. 19 is a diagram illustrating impedance characteristics of the elastic wave resonators of Example 2 and Comparative Example 1. In FIG.

[0107] The impedance characteristics of the main mode of the elastic wave resonator are shown in Fig. 19. As shown in Fig. 19, elastic wave resonator 10 of Example 2 has an impedance ratio equivalent to that of elastic wave resonator 510 of Comparative Example 1. In other words, the characteristics of the main mode are maintained in elastic wave resonator 10 of Example 2.

[0108] FIG. 20 is a diagram illustrating the return losses of the acoustic wave resonators of Example 2 and Comparative Example 1. In FIG.

[0109] The return loss of the main mode of the acoustic wave resonator is shown in Fig. 20. As shown in Fig. 20, acoustic wave resonator 10 of Example 2 has a suppressed longitudinal mode response compared to acoustic wave resonator 510 of Comparative Example 1.

[0110] FIG. 21 is a diagram illustrating impedance phase characteristics of the elastic wave resonators of Example 2 and Comparative Example 1. In FIG.

[0111] 21 shows the response of Rayleigh waves occurring outside the band. As shown in FIG. 21, the response of Rayleigh waves in elastic wave resonator 10 of Example 2 is suppressed compared to elastic wave resonator 510 of Comparative Example 1.

[0112] As described above, acoustic wave resonator 10 according to the second embodiment can suppress unwanted waves more effectively than comparative example 1.

[0113] [Elastic wave resonators of Examples 3, 4, 5, 6, and 7] The following describes acoustic wave resonators 10 according to Examples 3 to 7, which are examples of the first embodiment. Examples 3 to 7 have the basic configuration of Example 2, and the duty of divided region D is changed differently.

[0114] First, the third embodiment will be described.

[0115] Fig. 22A is a diagram showing changes in duty of divided region D in a predetermined second divided region group in Example 3. Fig. 22B is a diagram showing changes in duty of divided region D in a plurality of second divided region groups B1 to B7 in Example 3.

[0116] These figures show coordinates in which the first axis represents the array number of the electrode fingers 11a, 11b arranged in order in the first direction d1, and the second axis represents the duty. Specifically, the second axis represents a function related to the weight of the duty. This coordinate system is similar in the following figures.

[0117] 22A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in FIG. 22A, the divided region D is formed so that the duty of the divided region D describes a sawtooth wave shape at this coordinate. FIG. 22B shows how the duty of each divided region D located in the multiple second divided region groups B1 to B7 changes depending on the coordinate position on the first axis. As shown in FIG. 22B, the multiple divided regions D are formed so that the duties of each divided region D describe multiple waveforms that have the same shape but different phases at this coordinate.

[0118] Next, a fourth embodiment will be described.

[0119] Fig. 23A is a diagram showing changes in duty of divided region D in a predetermined second divided region group in Example 4. Fig. 23B is a diagram showing changes in duty of divided region D in a plurality of second divided region groups B1 to B7 in Example 4.

[0120] Fig. 23A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in Fig. 23A, the divided region D is formed so that the duties of the divided region D describe multiple triangular wave shapes at this coordinate. Fig. 23B shows how the duties of the divided regions D located in multiple second divided region groups B1 to B7 change depending on the coordinate position on the first axis. As shown in Fig. 23B, the multiple divided regions D are formed so that the duties of each of the multiple divided regions D describe multiple waveforms that have the same shape but different phases at this coordinate.

[0121] Next, a fifth embodiment will be described.

[0122] 24A is a diagram showing changes in duty of divided region D in a predetermined second divided region group in Example 5. FIG. 24B is a diagram showing changes in duty of divided region D in a plurality of second divided region groups B1 to B7 in Example 5.

[0123] FIG. 24A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in FIG. 24A, the divided region D is formed so that the duty of the divided region D changes in a curved manner, specifically, in one cycle of a curved wave shape, at this coordinate. The curved wave shape is, for example, a sine wave shape. FIG. 24B shows how the duty of each divided region D located in multiple second divided region groups B1 to B7 changes depending on the coordinate position on the first axis. As shown in FIG. 24B, the multiple divided regions D are formed so that the duties of each divided region D at this coordinate describe multiple waveforms with the same shape but different phases.

[0124] Next, a sixth embodiment will be described.

[0125] 25A is a diagram showing changes in duty of divided region D in a predetermined second divided region group in Example 6. Fig. 25B is a diagram showing changes in duty of divided region D in a plurality of second divided region groups B1 to B7 in Example 6.

[0126] 25A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in FIG. 25A, the divided region D is formed so that the duty of the divided region D changes in a curved wave shape of less than one period or less than 1 / 2 period at this coordinate. FIG. 25B shows how the duty of the divided regions D located in the multiple second divided region groups B1 to B7 changes depending on the coordinate position on the first axis. As shown in FIG. 25B, the multiple divided regions D are formed so that the duties of each of the multiple divided regions D draw multiple waveforms with the same shape but different phases at this coordinate.

[0127] Next, a seventh embodiment will be described.

[0128] Fig. 26A is a diagram showing changes in duty of divided region D in a predetermined second divided region group in Example 7. Fig. 26B is a diagram showing changes in duty of divided region D in a plurality of second divided region groups B1 to B7 in Example 7.

[0129] Fig. 26A shows how the duty of a divided region D located in the second divided region group B1 changes depending on the coordinate position on the first axis. As shown in Fig. 26A, the divided region D is formed so that the duty of the divided region D changes in a curved wave shape with more than one period at this coordinate. Fig. 26B shows how the duty of the divided regions D located in the multiple second divided region groups B1 to B7 changes depending on the coordinate position on the first axis. As shown in Fig. 26B, the multiple divided regions D are formed so that the duties of each of the multiple divided regions D draw multiple waveforms with the same shape but different phases at this coordinate.

[0130] FIG. 27 is a diagram showing impedance phase characteristics of the acoustic wave resonators 10 according to the first, second, and third examples.

[0131] The response of Rayleigh waves occurring outside the band is shown in Fig. 27. As shown in Fig. 27, the response of Rayleigh waves is suppressed in each of acoustic wave resonators 10 according to Examples 1, 2, and 3.

[0132] FIG. 28 is a diagram showing impedance phase characteristics of the acoustic wave resonators 10 according to the first, fifth, and sixth examples.

[0133] The response of Rayleigh waves occurring outside the band is shown in Fig. 28. As shown in Fig. 28, the Rayleigh waves are dispersed in the acoustic wave resonators 10 of Examples 5 and 6 differently from Example 1, and the Rayleigh wave response is suppressed more than in Example 1.

[0134] FIG. 29 is a diagram showing the maximum values ​​of unwanted responses of Rayleigh waves in Examples 1, 2, 3, 5, and 6 and Comparative Example 1.

[0135] Fig. 29 shows the maximum value of the unwanted response of the Rayleigh wave when Comparative Example 1 is used as a reference. As shown in Fig. 29, Examples 1, 2, 3, 5, and 6 have smaller maximum values ​​of the unwanted response of the Rayleigh wave than Comparative Example 1. Furthermore, Examples 5 and 6 have smaller maximum values ​​of the unwanted response of the Rayleigh wave than Examples 1, 2, and 3.

[0136] [Elastic Wave Resonator of Example 8] Elastic wave resonator 10 according to Example 8, which is one of examples of Embodiment 1, will be described with reference to Fig. 30 and Fig. 31. Example 8 describes an example in which the duties and electrode finger pitches of divided regions D are randomly formed.

[0137] FIG. 30 is a diagram illustrating an example of the IDT electrode 11 of the acoustic wave resonator 10 according to the eighth embodiment.

[0138] Acoustic wave resonator 10 includes IDT electrode 11 and a plurality of reflectors 12. IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B that face each other.

[0139] The interdigital electrode 11A is composed of a plurality of electrode fingers 11a arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the electrode fingers 11a to each other. The interdigital electrode 11B is composed of a plurality of electrode fingers 11b arranged to extend in the second direction d2 and a busbar electrode 11c connecting one ends of the electrode fingers 11b to each other. The electrode fingers 11a and 11b are arranged alternately along the first direction d1.

[0140] The reflector 12 is arranged next to the IDT electrode 11 in the first direction d1. The multiple reflectors 12 are arranged on both outer sides of the IDT electrode 11. The reflector 12 is composed of multiple reflective electrode fingers 12a arranged to extend in the second direction d2 and busbar electrodes 12c connecting one ends of the multiple reflective electrode fingers 12a to each other.

[0141] In the region where the IDT electrodes 11 are formed, a plurality of first divided region groups A1 to A21, a plurality of second divided region groups B1 to B7, and a plurality of divided regions D are formed.

[0142] The multiple first divided region groups A1 to A21 are formed in a region on the main surface 100a of the piezoelectric layer 100 where the IDT electrode 11 is formed, and are aligned along the first direction d1. Each of the multiple first divided region groups A1 to A21 is formed by a region including one or more electrode fingers 11a (or 11b). In this example, each of the first divided region groups A1 to A21 is formed by a region including only one electrode finger. Each of the first divided region groups A1 to A21 is formed to include the entire longitudinal length of the electrode finger extending in the second direction d2.

[0143] The second divided region groups B1 to B7 are arranged in the second direction d2 in the region where the IDT electrode 11 is formed. Specifically, the second divided region groups B1 to B7 are formed in an intersection region T1 where the electrode fingers 11a, 11b intersect within the region where the IDT electrode 11 is formed. Each of the second divided region groups B1 to B7 intersects with the electrode fingers 11a, 11b. In this example, each of the second divided region groups B1 to B7 is formed across 21 of the electrode fingers 11a, 11b.

[0144] The plurality of divided regions D are arranged in a matrix along the first direction d1 and the second direction d2 in the region where the IDT electrode 11 is formed. The plurality of divided regions D are regions defined by a plurality of first divided region groups A1 to A21 and a plurality of second divided region groups B1 to B7, and are formed in a matrix by being partitioned by the first divided region groups A1 to A21 and the second divided region groups B1 to B7. In this example, the plurality of divided regions D are configured by 21 in the first direction d1 and 7 in the second direction d2, for a total of 147 divided regions.

[0145] Each divided region D is a region that includes a portion of the multiple electrode fingers 11a, 11b and a portion of the electrode fingers in the longitudinal direction. In this example, each divided region D is a region that includes one electrode finger and 1 / 7 of the length of the electrode finger in the longitudinal direction. The multiple divided regions D all have the same length in the first direction d1, and the multiple divided regions D all have the same length in the second direction d2. Within each of the multiple divided regions D, the electrode duty and the electrode finger pitch are constant.

[0146] Each of the first divided region groups A1 to A21 includes one divided region Ba and another divided region Bb adjacent to each other in the second direction d2. In this embodiment, the duty in the one divided region Ba is larger than the duty in the other divided region Bb, and the electrode finger pitch in the one divided region Ba is smaller than the electrode finger pitch in the other divided region Bb.

[0147] Each of the multiple second divided area groups B1 to B7 includes one divided area Aa and another divided area Ab adjacent to each other in the first direction d1. In this embodiment, the duty in one divided area Aa is larger than the duty in the other divided area Ab, and the electrode finger pitch in one divided area Aa is smaller than the electrode finger pitch in the other divided area Ab. In Fig. 30, the hatching of the electrode fingers in each divided area D in each second divided area group is the same, but in reality, the duties of each divided area D are different.

[0148] In this embodiment, in one divided region Aa and the other divided region Ab adjacent to each other in the first direction d1, the resonance frequency determined based on the duty and electrode finger pitch of one divided region Aa and the resonance frequency determined based on the duty and electrode finger pitch of the other divided region Ab are formed to match each other. Also, in one divided region Ba and the other divided region Bb adjacent to each other in the second direction d2, the resonance frequency determined based on the duty and electrode finger pitch of one divided region Ba and the resonance frequency determined based on the duty and electrode finger pitch of the other divided region Bb are formed to match each other.

[0149] Furthermore, in this embodiment, the duties of the multiple divided regions D are configured to change randomly. For example, it is desirable that the duties of all adjacent divided regions D are different, but this is not limited thereto, and the duties of some adjacent divided regions D may be the same. In other words, it is sufficient that the duties of the multiple divided regions D are different at least in some of the adjacent divided regions D. The electrode finger pitch is set so that the resonance frequencies of the respective divided regions D are approximately the same.

[0150] In this way, by configuring the duty of the divided region D to change randomly, it is possible to distribute the frequencies of unwanted waves such as longitudinal modes and Rayleigh waves. This makes it possible to prevent unwanted waves from becoming large. Furthermore, by matching the resonant frequencies of the main modes, it is possible to prevent a decrease in the impedance ratio and suppress deterioration of the main mode characteristics.

[0151] FIG. 31 is a diagram illustrating another example of the IDT electrodes of the acoustic wave resonator according to the eighth embodiment.

[0152] An acoustic wave resonator 10 according to the eighth embodiment has an IDT electrode 11 and a plurality of reflectors 12. Fig. 31 is a schematic diagram, and the number of pairs of electrode fingers is different in reality. For example, the number of pairs of electrode fingers 11a, 11b of the IDT electrode 11 is 158 pairs, and the number of pairs of reflecting electrode fingers 12a of the reflector 12 is 10 pairs.

[0153] 31, the IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B. Each of the pair of comb-shaped electrodes 11A and 11B has a plurality of electrode fingers 11a and 11b, and a first bus bar electrode 31 connecting one end of each of the plurality of electrode fingers 11a and 11b. The duty and electrode finger pitch patterns in the plurality of divided regions D are different from each other.

[0154] 31 , each of the pair of comb-shaped electrodes 11A and 11B has a second bus bar electrode 32 that is thinner than the first bus bar electrode 31. In this example, the reflector 12 also has a second bus bar electrode 34 that is thinner than the bus bar electrode 12c. The IDT electrode 11 also has piston mode forming regions 35 that are located at both end portions 36 of the electrode fingers 11a and 11b. The acoustic wave resonator 10 of the eighth embodiment can suppress unwanted waves.

[0155] [Other Examples] Other embodiments of the acoustic wave resonator 10 will now be described.

[0156] In the above example, the duty change amount is 0.5±0.03, but it is not limited to this and may be 0.5±0.05 or 0.5±0.07. Note that while increasing the change amount can disperse unwanted responses, increasing the change amount too much will degrade the main mode characteristics, so the duty change amount may be 0.5±0.2 or less.

[0157] In the above example, the duty of reflector 12 is constant, but this is not limiting. For example, acoustic wave resonator 10 may be divided into a plurality of divided regions including IDT electrode 11 and reflector 12, with each divided region having a different duty. The shape of the divided regions is not limited to a rectangular shape, and may be a square, polygonal, or curved shape.

[0158] When the elastic wave resonator is configured with a plurality of split resonators, a split region may be formed for each of the plurality of split resonators, and the duty may be made different for each split region.

[0159] The frequency of unwanted waves may be dispersed by adjusting the electrode film thickness and the protective film thickness in addition to the duty. The parameters to be adjusted are not limited to the duty, but may also be at least one of the electrode finger pitch, the electrode film thickness, the protective film thickness, and the film thickness of the laminated substrate including the piezoelectric layer, or a combination of these.

[0160] The piezoelectric layer 100 is not limited to LT, but may be LN (lithium niobate). Furthermore, the piezoelectric layer 100 is not limited to the above orientation and cut angle.

[0161] Furthermore, IDT electrode 11 of acoustic wave resonator 10 may be applied to an IDT that forms longitudinal coupling.

[0162] 32 to 39 are diagrams showing other examples of cross sections of acoustic wave resonator 10. FIG.

[0163] The substrate that forms the acoustic wave may be a single piezoelectric single crystal substrate, or may be a composite substrate in which a piezoelectric layer and a support substrate are bonded together.

[0164] The composite substrate may have a layered structure of a piezoelectric layer / low acoustic velocity layer / high acoustic velocity layer / support substrate (see FIG. 32). The composite substrate may be composed of a piezoelectric layer / support substrate, or may have a configuration in which a multilayer reflective layer made up of a low acoustic impedance film and a high acoustic impedance film is provided between the piezoelectric layer and the support substrate (see FIG. 33). Furthermore, in the above configuration, the IDT electrode 11 may be covered with a first protective film (temperature compensation film) and a second protective film (moisture-resistant film) (see FIG. 34). A dielectric film may be formed between the IDT electrode 11 and the piezoelectric layer.

[0165] Alternatively, hollow region 160 may be formed below the piezoelectric layer (see FIG. 35). Alternatively, a structure in which an electrode is provided inside hollow region 160, i.e., a double-sided IDT structure in which IDT electrodes 11 are provided on both sides of the piezoelectric layer, may be used (see FIG. 36). An IDT pattern in phase with or opposite to that on the front surface may be formed on the back surface of the piezoelectric layer. The electrode inside hollow region 160 may be a solid electrode (flat electrode) instead of IDT electrode 11 (see FIG. 37). The solid electrode may be set to ground potential, or may be a floating electrode that is not connected to any other electrode.

[0166] The IDT electrode 11 on the back surface of the piezoelectric layer may be filled with a low acoustic velocity layer material instead of being provided in the hollow region 160 (see FIG. 38). Also, the electrode on the back surface of the piezoelectric layer may be formed as a solid electrode instead of the IDT electrode 11 (see FIG. 39).

[0167] (Embodiment 2) In the second embodiment, a ladder-type acoustic wave filter device using the acoustic wave resonator 10 according to the first embodiment will be described.

[0168] 40 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.

[0169] 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 reference terminal (ground) and the connection points of the terminal 50, the series arm resonators s11 to s15, and the terminal 60, respectively. The above-described connection configuration of the series arm resonators s11 to s15 and the parallel arm resonators p11 to p14 configures the acoustic wave filter device 1 as 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.

[0170] In the second embodiment, all of the series arm resonators s11 to s15 and the parallel arm resonators p11 to p14 included in the acoustic wave filter device 1 may be configured with the above-described acoustic wave resonator 10. Alternatively, only the parallel arm resonators p11 to p14 included in the acoustic wave filter device 1 may be configured with the above-described acoustic wave resonator 10. Alternatively, only the parallel arm resonator p14 or the series arm resonator s15, which is closest to the terminal 50 connected to the common terminal, may be configured with the above-described acoustic wave resonator 10.

[0171] The acoustic wave filter device 1 may have any configuration as long as it includes the configuration of the acoustic wave resonator 10 according to the first embodiment. The circuit configuration shown in Fig. 40 is just 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. 40. Furthermore, although a ladder-type circuit configuration is illustrated in Fig. 40, a longitudinally coupled resonator circuit may also be included.

[0172] (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.

[0173] 41 is a diagram illustrating a circuit configuration of a multiplexer 5 and its peripheral circuit (antenna 4) according to Embodiment 3. The multiplexer 5 illustrated in the diagram includes an acoustic wave filter device 1, a filter 3, a common terminal 70, and input / output terminals 81 and 82.

[0174] 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.

[0175] The filter 3 is connected to the common terminal 70 and the 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 also be an LC filter or the like, and its circuit configuration is not particularly limited. The pass band of the acoustic wave filter device 1 may be located on the lower frequency side than the pass band of the filter 3.

[0176] 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. 41, 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.

[0177] 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.

[0178] In other words, the multiplexer of the present invention comprises a plurality of filters including the acoustic wave filter device 1, and the input / output terminals and one of the input / output terminals of each of the plurality of filters are connected directly or indirectly to a common terminal, and at least one of the plurality of filters excluding the acoustic wave filter device 1 may have a passband with a frequency higher than the passband frequency of the acoustic wave filter device 1.

[0179] (summary) An example of an elastic wave resonator of the present invention will be described below.

[0180] The elastic wave resonator 10 of Example 1 includes a piezoelectric layer 100 and an IDT electrode 11 formed on a principal surface 100a of the piezoelectric layer 100. The IDT electrode 11 has a plurality of electrode fingers 11a and 11b. The electrode fingers 11a and 11b are arranged in a first direction d1 along the principal surface 100a of the piezoelectric layer 100. The region on the principal surface 100a of the piezoelectric layer 100 where the IDT electrode 11 is formed has a plurality of divided regions D arranged in a matrix along the first direction d1 and a second direction d2 in which the electrode fingers 11a and 11b extend. Each divided region D includes a portion of the electrode fingers 11a and 11b and a portion of the electrode fingers in the longitudinal direction. The divided regions D include one divided region Ba and another divided region Bb adjacent to each other in the second direction d2. The duty in one divided region Ba is larger than the duty in the other divided region Bb, and the electrode finger pitch in one divided region Ba is smaller than the electrode finger pitch in the other divided region Bb.

[0181] In this way, by making the duties different between the divided regions Ba and Bb adjacent to each other in the second direction d2, it is possible to distribute the frequencies at which unwanted waves occur, thereby preventing the unwanted waves from becoming large.

[0182] An elastic wave resonator 10 of Example 2 is the elastic wave resonator described in Example 1, wherein the multiple divided regions D include one divided region Aa and another divided region Ab adjacent to each other in a first direction d1. The duty in the one divided region Aa may be larger than the duty in the other divided region Ab, and the electrode finger pitch in the one divided region Aa may be smaller than the electrode finger pitch in the other divided region Ab.

[0183] In this way, by making the duties different between the divided regions Aa and Ab adjacent to each other in the first direction d1, it is possible to distribute the frequencies at which unwanted waves occur, thereby preventing the unwanted waves from becoming large.

[0184] The elastic wave resonator 10 of Example 3 is the elastic wave resonator described in Example 1 or 2, and in one divided region Aa and the other divided region Ab adjacent to each other in the first direction d1, the resonant frequency determined based on the duty and electrode finger pitch of the one divided region Aa and the resonant frequency determined based on the duty and electrode finger pitch of the other divided region Ab may be formed to match each other, and in one divided region Ba and the other divided region Bb adjacent to each other in the second direction d2, the resonant frequency determined based on the duty and electrode finger pitch of the one divided region Ba and the resonant frequency determined based on the duty and electrode finger pitch of the other divided region Bb may be formed to match each other.

[0185] By matching the resonant frequencies in this way, it is possible to suppress a decrease in the impedance ratio and to suppress deterioration of the main mode characteristics.

[0186] Acoustic wave resonator 10 of Example 4 is the acoustic wave resonator according to any one of Examples 1 to 3, and in each of the plurality of divided regions D, the duty and the electrode finger pitch may be constant.

[0187] This makes it possible to easily match the resonance frequencies of the divided regions D. This makes it possible to suppress a decrease in the impedance ratio and to suppress deterioration of the main mode characteristics.

[0188] The elastic wave resonator 10 of Example 5 is the elastic wave resonator according to any one of Examples 1 to 4, and the lengths of the multiple divided regions D in the first direction d1 may be the same, and the lengths of the multiple divided regions D in the second direction d2 may be the same.

[0189] This makes it possible to easily match the resonance frequencies of the divided regions D. This makes it possible to suppress a decrease in the impedance ratio and to suppress deterioration of the main mode characteristics.

[0190] The elastic wave resonator 10 of Example 6 is the elastic wave resonator according to any one of Examples 1 to 5, and the plurality of divided regions D may be formed so that the predetermined duty changes and moves continuously in the first direction d1 and the second direction d2.

[0191] In this way, by forming the duty of the divided region D so that it moves and changes continuously, it is possible to appropriately distribute the frequencies at which unwanted waves occur, thereby preventing the unwanted waves from becoming large.

[0192] The elastic wave resonator 10 of Example 7 is the elastic wave resonator according to any one of Examples 1 to 5, and the divided region D may be formed so that the duty of the divided region D changes linearly in at least a part of a coordinate range in which the first axis is the array number of the plurality of electrode fingers 11a, 11b arranged in order in the first direction d1 and the second axis is the duty.

[0193] In this way, by forming the duty of the divided region D so as to change linearly, it is possible to appropriately distribute the frequencies at which unwanted waves occur, thereby suppressing the unwanted waves from becoming large.

[0194] Elastic wave resonator 10 of Example 8 is the elastic wave resonator according to Example 7, and divided region D may be formed so that the duty of divided region D changes linearly and continuously in the coordinate system.

[0195] This allows the frequencies at which unwanted waves are generated to be dispersed appropriately, thereby preventing unwanted waves from becoming too large.

[0196] Elastic wave resonator 10 of Example 9 is the elastic wave resonator described in Example 7, and divided region D may be formed so that the duty of divided region D describes a triangular wave shape in the above coordinates.

[0197] This allows the frequencies at which unwanted waves are generated to be dispersed appropriately, thereby preventing unwanted waves from becoming too large.

[0198] Elastic wave resonator 10 of Example 10 is the elastic wave resonator described in Example 7, and divided region D may be formed so that the duty of divided region D describes a sawtooth waveform in the above coordinate system.

[0199] This allows the frequencies at which unwanted waves are generated to be dispersed appropriately, thereby preventing unwanted waves from becoming too large.

[0200] The elastic wave resonator 10 of Example 11 is the elastic wave resonator described in Example 7, and the multiple divided regions D may be formed so that, at the above coordinates, the duties of each of the multiple divided regions D describe multiple waveforms that have the same shape but different phases.

[0201] In this way, by forming the duty of the divided region D so as to draw a plurality of waveforms, it is possible to appropriately distribute the frequencies at which unwanted waves occur, thereby suppressing the unwanted waves from becoming large.

[0202] The elastic wave resonator 10 of Example 12 is the elastic wave resonator according to any one of Examples 1 to 5, and the divided region D may be formed so that the duty of the divided region D changes in a curved manner in at least a part of a coordinate range in which the first axis is the array number of the plurality of electrode fingers 11a, 11b arranged in order in the first direction d1 and the second axis is the duty.

[0203] In this way, by forming the duty of the divided region D so that it changes in a curved line, it is possible to appropriately distribute the frequencies at which unwanted waves occur, thereby suppressing the unwanted waves from becoming large.

[0204] The elastic wave resonator 10 of Example 13 is the elastic wave resonator described in Example 12, and the divided region D may be formed so that the duty of the divided region D describes a curved wave shape in the above coordinates that is less than one period or more than one period.

[0205] This allows the frequencies at which unwanted waves are generated to be dispersed appropriately, thereby preventing unwanted waves from becoming too large.

[0206] The elastic wave resonator 10 of Example 14 is the elastic wave resonator described in Example 12, and the multiple divided regions D may be formed so that, at the above coordinates, the duties of each of the multiple divided regions D describe multiple waveforms that have the same shape but different phases.

[0207] In this way, by forming the duty of the divided region D so as to draw a plurality of waveforms, it is possible to appropriately distribute the frequencies at which unwanted waves occur, thereby suppressing the unwanted waves from becoming large.

[0208] An elastic wave resonator 10 of Example 15 is the elastic wave resonator according to any one of Examples 1 to 14, in which the IDT electrode 11 has piston mode forming regions 35 located at both end portions 36 of the electrode fingers 11a and 11b. The piston mode forming regions 35 may be included in the divided regions D located at both ends in the second direction d2, among the plurality of divided regions D.

[0209] According to this configuration, piston action is applied to the IDT, and deterioration of the main mode characteristics can be suppressed.

[0210] The elastic wave resonator 10 of Example 16 is the elastic wave resonator according to any one of Examples 1 to 15, and furthermore, the IDT electrode 11 has a pair of comb-shaped electrodes 11A and 11B, each of the pair of comb-shaped electrodes 11A and 11B having a plurality of electrode fingers 11a and 11b and a first bus bar electrode 31 connecting one ends of the plurality of electrode fingers 11a and 11b, and a high acoustic velocity portion 39 may be provided between both end portions 36 of the electrode fingers 11a and 11b and the first bus bar electrode 31.

[0211] An elastic wave resonator 10 of Example 17 is the elastic wave resonator according to any one of Examples 1 to 16, wherein the IDT electrode 11 further includes a pair of comb-shaped electrodes 11A and 11B. Each of the pair of comb-shaped electrodes 11A and 11B includes a plurality of electrode fingers 11a and 11b, a first busbar electrode 31 connecting one ends of the plurality of electrode fingers 11a and 11b, and a second busbar electrode 32 that is thinner than the first busbar electrode 31. The second busbar electrode 32 may be provided between the first busbar electrode 31 and the plurality of divided regions D and parallel to the first busbar electrode 31.

[0212] This configuration can prevent the main mode characteristics from deteriorating.

[0213] An acoustic wave resonator 10 of Example 18 is the acoustic wave resonator according to any one of Examples 1 to 17, and the piezoelectric layer 100 may be formed on a support substrate 150 .

[0214] The acoustic wave resonator 10 of Example 19 is the acoustic wave resonator described in Example 18, and may include a hollow region 160 between the piezoelectric layer 100 and the support substrate 150 .

[0215] The acoustic wave resonator 10 of Example 20 is the acoustic wave resonator described in Example 18, and may further include an intermediate layer 140 between the piezoelectric layer 100 and the support substrate 150 .

[0216] The elastic wave resonator 10 of Example 21 is the elastic wave resonator described in any one of Examples 1 to 16, and may further include a high acoustic velocity layer 130 in which the bulk wave acoustic velocity is faster than the elastic wave acoustic velocity in the piezoelectric layer 100, and a low acoustic velocity layer 120 disposed between the high acoustic velocity layer 130 and the piezoelectric layer 100 and in which the bulk wave acoustic velocity is slower than the elastic wave acoustic velocity in the piezoelectric layer 100.

[0217] This laminated structure can significantly increase the Q value of elastic wave resonator 10 at the resonant frequency and anti-resonant frequency. Since elastic wave resonator 10 with a high Q value can be configured, elastic wave resonator 10 can be used to configure a filter with low insertion loss.

[0218] An acoustic wave resonator 10 of Example 22 is the acoustic wave resonator according to any one of Examples 1 to 17, and the piezoelectric layer 100 may be a piezoelectric substrate.

[0219] An acoustic wave filter device 1 of Example 23 includes the acoustic wave resonator 10 according to any one of Examples 1 to 21.

[0220] This makes it possible to provide an acoustic wave filter device 1 including an acoustic wave resonator 10 capable of suppressing unwanted waves.

[0221] (Other embodiments, etc.) Although the acoustic wave resonators and acoustic wave filter devices according to the embodiments of the present invention have been described above with reference to the embodiments and examples, the acoustic wave resonators and acoustic wave filter devices of the present invention are not limited to the above embodiments and examples. The present invention also includes other embodiments realized by combining any of the components in the above embodiments and examples, examples obtained by applying various modifications to the above embodiments 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 resonators and acoustic wave filter devices of the present invention.

[0222] For example, a piezoelectric substrate having a piezoelectric layer may be formed in the following manner.

[0223] Examples of materials that can be used for the piezoelectric substrate 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, and forsterite; dielectrics such as diamond and glass; semiconductors such as silicon and gallium nitride; resins; and materials containing any of the above materials as a main component.

[0224] The piezoelectric substrate may be a substrate having a piezoelectric layer at least in a portion thereof, or may have a laminated structure having a piezoelectric layer. The piezoelectric substrate may have a structure including, for example, a high acoustic speed support substrate, a low acoustic speed film, and a piezoelectric layer, in which the high acoustic speed support substrate, the low acoustic speed film, and the piezoelectric layer are laminated in this order.

[0225] The configurations of the high acoustic velocity support substrate, the low acoustic velocity film, and the piezoelectric layer will be described below.

[0226] The piezoelectric layer is made of, for example, a θ° Y-cut X-propagation LiTaO3 piezoelectric single crystal or piezoelectric ceramic (a lithium tantalate single crystal or ceramic cut along a plane whose normal is an axis rotated θ° 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).

[0227] The high acoustic speed support substrate is a substrate that supports the low acoustic speed film, the piezoelectric layer, and the electrode 110. The high acoustic speed support substrate is also a substrate in which the acoustic speed of bulk waves in the high acoustic speed support substrate is faster than that of surface waves and boundary waves that propagate through the piezoelectric layer, and functions to confine the surface acoustic waves to the portion where the piezoelectric layer and the low acoustic speed film are laminated, preventing them from leaking below the high acoustic speed support substrate.

[0228] The high acoustic velocity support substrate is, for example, a silicon substrate. Materials for the high acoustic velocity support substrate include, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectric materials such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; semiconductors such as silicon; and materials containing the above materials as their main components. 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 MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0229] The low acoustic velocity film is a film in which the acoustic velocity of the bulk wave in the low acoustic velocity film is slower than the acoustic velocity of the elastic wave propagating through the piezoelectric layer, and is placed between the piezoelectric layer and the high acoustic velocity support substrate. This structure, together with the property that the energy of the elastic wave is concentrated in a medium with an essentially low acoustic velocity, suppresses the leakage of surface acoustic wave energy outside the IDT electrode.

[0230] The low acoustic velocity film is, for example, a film whose main component is silicon dioxide (SiO2). The material of the low acoustic velocity film is not limited to the above, and for example, dielectrics such as glass, silicon oxide, silicon oxynitride, lithium oxide, tantalum oxide, or compounds in which fluorine, carbon, or boron is added to silicon oxide, or materials whose main component is any of the above materials, can also be used.

[0231] The laminated structure of the piezoelectric substrate makes it possible to significantly increase the Q value of the surface acoustic wave resonator at the resonant frequency and anti-resonant frequency compared to a structure using a single layer of piezoelectric substrate. In other words, a surface acoustic wave resonator with a high Q value can be configured, and a filter with low insertion loss can be configured using the surface acoustic wave resonator.

[0232] The high acoustic velocity support substrate may have a laminated structure of a support substrate and a high acoustic velocity film that makes the acoustic velocity of the bulk waves that propagate through the piezoelectric layer faster than the acoustic velocity of the surface waves or boundary waves that propagate through the piezoelectric layer.

[0233] In the case of this laminated structure, the material of the support substrate can be selected from the following: piezoelectric materials such as sapphire, lithium tantalate, lithium niobate, and quartz; various ceramics such as alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectric materials such as glass; semiconductors such as silicon and gallium nitride; and resin substrates.

[0234] In addition, materials for the high acoustic velocity film can include, for example, piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel, and sialon; dielectric materials such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; semiconductors such as silicon; or materials containing the above materials as their main components. The spinel includes aluminum compounds containing oxygen and one or more elements selected from Mg, Fe, Zn, Mn, etc. Examples of the spinel include MgAl2O4, FeAl2O4, ZnAl2O4, and MnAl2O4.

[0235] The materials of the layers exemplified in the above laminated structure of the piezoelectric substrate are merely examples, and may be changed depending on, for example, the characteristics that are to be emphasized among the required high frequency propagation characteristics. [Industrial Applicability]

[0236] INDUSTRIAL APPLICABILITY The present invention can be widely used in communication devices such as mobile phones as an acoustic wave resonator and an acoustic wave filter device capable of suppressing unwanted waves. [Explanation of symbols]

[0237] 1. Elastic wave filter device 3. Filters 4 Antennas 5 Multiplexer 10. Elastic wave resonator 11 IDT electrode 11A, 11B comb-shaped electrode 11a, 11b electrode fingers 11c Busbar electrode 12 reflector 12a Reflector electrode finger 12c Busbar electrode 31 First bus bar electrode 32, 34 Second bus bar electrode 35 Piston mode formation region 36 end 37. Central Department 38 Loading membrane 39 Hypersonic Section 50, 60 terminals 70 common terminal 81, 82 Input / Output Terminals 100 Compressive Layer 100a Main face 110 electrode 111 Adhesive layer 112 Main Electrode Layer 113 Protective Film 120 Low Speed ​​Layer 130 Hypersonic Layer 140 Intermediate Layer 150 support base 160 Hollow Area A1, A2, A3, A4, A5, A6, A7 First Segmentation Domain Group Aa one party's divided area Ab The divided domain of others B1, B2, B3, B4, B5, B6, B7 Second Segmentation Domain Group Ba one side's divided area Bb Other's divided areas c1 centerline D Segmentation Domain d1 Direction 1 d2 Second direction p11, p12, p13, p14 Parallel wrist resonators s11, s12, s13, s14, s15 in-line wrist resonator T1 Intersection Area

Claims

1. a piezoelectric layer; an IDT electrode formed on a main surface of the piezoelectric layer; Equipped with the IDT electrode has a plurality of electrode fingers, the plurality of electrode fingers are arranged in a first direction along a principal surface of the piezoelectric layer, a region on the main surface of the piezoelectric layer where the IDT electrode is formed includes a plurality of divided regions arranged in a matrix along the first direction and a second direction in which the electrode fingers extend; the divided region is a region including a part of the electrode fingers among the plurality of electrode fingers and a part of the electrode fingers in the longitudinal direction, the plurality of divided regions include one divided region and another divided region adjacent to each other in the second direction, The duty in the one divided region is larger than the duty in the other divided region, and the electrode finger pitch in the one divided region is smaller than the electrode finger pitch in the other divided region. Elastic wave resonator.

2. the plurality of divided regions include one divided region and another divided region adjacent to each other in the first direction, The duty in the one divided region is larger than the duty in the other divided region, and the electrode finger pitch in the one divided region is smaller than the electrode finger pitch in the other divided region. The elastic wave resonator according to claim 1 .

3. in the one divided region and the other divided region adjacent to each other in the first direction, a resonance frequency determined based on the duty and the electrode finger pitch of the one divided region and a resonance frequency determined based on the duty and the electrode finger pitch of the other divided region are formed to match each other, In the one divided region and the other divided region adjacent to each other in the second direction, a resonance frequency determined based on the duty and the electrode finger pitch of the one divided region and a resonance frequency determined based on the duty and the electrode finger pitch of the other divided region are formed to match each other. The elastic wave resonator according to claim 2 .

4. In each of the plurality of divided regions, the duty is constant and the electrode finger pitch is constant. The elastic wave resonator according to any one of claims 1 to 3.

5. The lengths of the plurality of divided regions in the first direction are the same, The lengths of the plurality of divided regions in the second direction are the same. The elastic wave resonator according to any one of claims 1 to 3.

6. The plurality of divided regions are formed so that the predetermined duty continuously moves and changes in the first direction and the second direction. The elastic wave resonator according to any one of claims 1 to 3.

7. The divided regions are formed so that the duty of the divided regions changes linearly in at least a part of a coordinate range in which the first axis is the array number of the plurality of electrode fingers arranged in order in the first direction and the second axis is the duty. The elastic wave resonator according to any one of claims 1 to 3.

8. The divided regions are formed so that the duty of the divided regions changes linearly and continuously at the coordinates. The elastic wave resonator according to claim 7 .

9. The divided regions are formed so that the duty of the divided regions forms a triangular wave shape at the coordinates. The elastic wave resonator according to claim 7 .

10. The divided regions are formed so that the duty of the divided regions forms a sawtooth wave shape at the coordinates. The elastic wave resonator according to claim 7 .

11. The divided regions are formed in such a manner that the duties of the divided regions respectively depict a plurality of waveforms having the same shape but different phases at the coordinates. The elastic wave resonator according to claim 7 .

12. The divided regions are formed so that the duty of the divided regions changes in a curved line in at least a part of a coordinate range in which the first axis is the array number of the plurality of electrode fingers arranged in order in the first direction and the second axis is the duty. The elastic wave resonator according to claim 2 .

13. The divided regions are formed so that the duty of the divided regions draws a curved wave shape that is less than one cycle or more than one cycle at the coordinates. The elastic wave resonator according to claim 12.

14. The divided regions are formed in such a manner that the duties of the divided regions respectively depict a plurality of waveforms having the same shape but different phases at the coordinates. The elastic wave resonator according to claim 12.

15. the IDT electrode has piston mode forming regions located at both ends of the electrode fingers, The piston mode forming region is included in the divided regions located at both ends in the second direction among the plurality of divided regions. The elastic wave resonator according to any one of claims 1 to 3.

16. Furthermore, the IDT electrode has a pair of comb-shaped electrodes, each of the pair of comb-shaped electrodes includes the plurality of electrode fingers and a first bus bar electrode connecting one ends of the plurality of electrode fingers to each other; A high acoustic velocity portion is provided between both ends of the electrode finger and the first bus bar electrode. The elastic wave resonator according to any one of claims 1 to 3.

17. Furthermore, the IDT electrode has a pair of comb-shaped electrodes, each of the pair of comb-like electrodes includes the plurality of electrode fingers, a first bus bar electrode connecting one ends of the plurality of electrode fingers to each other, and a second bus bar electrode narrower than the first bus bar electrode; The second bus bar electrode is provided between the first bus bar electrode and the plurality of divided regions and parallel to the first bus bar electrode. The elastic wave resonator according to any one of claims 1 to 3.

18. The piezoelectric layer is formed on a support substrate. The elastic wave resonator according to any one of claims 1 to 3.

19. A hollow region is provided between the piezoelectric layer and the support substrate. The elastic wave resonator according to claim 18.

20. An intermediate layer is provided between the piezoelectric layer and the support substrate. The elastic wave resonator according to claim 18.

21. a high acoustic velocity layer in which a bulk wave propagates at a higher acoustic velocity than an elastic wave propagating through the piezoelectric layer; a low acoustic velocity layer disposed between the high acoustic velocity layer 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 elastic wave resonator according to any one of claims 1 to 3.

22. The piezoelectric layer is a piezoelectric substrate. The elastic wave resonator according to any one of claims 1 to 3.

23. An acoustic wave filter device comprising the acoustic wave resonator according to any one of claims 1 to 3.

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