Elastic wave filter, multiplexer, high-frequency front-end circuit, and communication device

Abstract

An elastic wave filter is an elastic wave filter including a plurality of elastic wave resonators using bulk waves of a thickness longitudinal vibration mode, and includes a series arm resonator and a parallel arm resonator configured using the elastic wave resonators. The series arm resonator and the parallel arm resonator each have a piezoelectric body, an upper electrode provided above the piezoelectric body, a lower electrode provided below the piezoelectric body, and a lead wire connected to at least one of the upper electrode and the lower electrode. The upper electrode and the lower electrode are opposed in a first direction in plan view. When a ratio of a length (Wa1) of at least one of the upper electrode and the lower electrode in the first direction to a length (Wb1) in a second direction perpendicular to the first direction is set as an aspect ratio (Wb1 / Wa1), the aspect ratio (Wb1 / Wa1) of the series arm resonator is larger than the aspect ratio (Wb1 / Wa1) of the parallel arm resonator.

Description

Technical Field

[0001] This invention relates to elastic wave filters, multiplexers, high-frequency front-end circuits, and communication devices. Background Technology

[0002] Patent Document 1 describes a slender elastic wave resonator with a two-dimensional shape whose long side of the electrode is more than twice the size of the short side (in Patent Document 1, it is a piezoelectric thin film device).

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-042871 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In elastic wave filters constructed using multiple such elastic wave resonators, improved filter characteristics are required. However, directly applying the elastic wave resonator of Patent Document 1 to an elastic wave filter, and making the electrodes of the resonator elongated, can potentially degrade Q and increase filter losses.

[0008] The purpose of this invention is to provide elastic wave filters, multiplexers, high-frequency front-end circuits, and communication devices that can improve filter characteristics.

[0009] Technical solutions for solving the problem

[0010] One type of elastic wave filter involves a plurality of elastic wave resonators comprising a body wave utilizing a thickness longitudinal vibration mode. The filter includes a series arm resonator and a parallel arm resonator constructed using the elastic wave resonators. Each of the series arm resonator and the parallel arm resonator has: a piezoelectric body; an upper electrode disposed above the piezoelectric body; a lower electrode disposed below the piezoelectric body; and lead-out wiring connected to at least one of the upper and lower electrodes. Viewed from above, the upper and lower electrodes are sandwiched and opposed in a first direction. When the ratio of the length (Wa1) of at least one of the upper and lower electrodes in the first direction to its length (Wb1) in a second direction perpendicular to the first direction is defined as the aspect ratio (Wb1 / Wa1), the aspect ratio (Wb1 / Wa1) of the series arm resonator is greater than the aspect ratio (Wb1 / Wa1) of the parallel arm resonator.

[0011] One approach involves a multiplexer having multiple filters including the aforementioned elastic wave filter, wherein one of the input terminals and one of the output terminals of each of the multiple filters are electrically connected to each other.

[0012] One approach involves a high-frequency front-end circuit that includes the aforementioned elastic wave filter.

[0013] One approach involves a high-frequency front-end circuit that includes the aforementioned multiplexer.

[0014] One method involves a communication device that includes the aforementioned high-frequency front-end circuit.

[0015] Invention Effects

[0016] The elastic wave filter, multiplexer, high-frequency front-end circuit, and communication device according to the present invention can improve filter characteristics. Attached Figure Description

[0017] Figure 1 This is a circuit diagram showing the elastic wave filter according to the first embodiment.

[0018] Figure 2 This is a schematic cross-sectional view showing the structure of the elastic wave filter according to the first embodiment.

[0019] Figure 3 This is a top view schematically showing the structure of the resonator chip in the elastic wave filter according to the first embodiment.

[0020] Figure 4 This is a top view schematically showing the surface of the module substrate in the elastic wave filter according to the first embodiment.

[0021] Figure 5 This is a schematic top view showing the inner layer of the module substrate in the elastic wave filter according to the first embodiment.

[0022] Figure 6 This is a schematic top view of the back side of the module substrate in the elastic wave filter according to the first embodiment.

[0023] Figure 7 This is a top view showing the structure of the series arm resonator in the elastic wave filter according to the first embodiment.

[0024] Figure 8 yes Figure 7 Sectional view of VIII-VIII'.

[0025] Figure 9 This is a top view showing the structure of the upper electrode and the frame electrode.

[0026] Figure 10 This is a top view showing the structure of the upper electrode and the frame electrode involved in the first modified example.

[0027] Figure 11This is a top view showing the structure of the upper electrode and the frame electrode involved in the second modified example.

[0028] Figure 12 This is a top view showing the structure of the upper electrode and the frame electrode involved in the third modified example.

[0029] Figure 13 This is a cross-sectional view showing the structure of the upper electrode and the frame electrode involved in the fourth modified example.

[0030] Figure 14 This is a top view showing the structure of the series arm resonator involved in the fifth variation.

[0031] Figure 15 This is a coordinate graph showing the filter characteristics of the elastic wave filter involved in Embodiment 1.

[0032] Figure 16 This is a coordinate graph showing the filter characteristics of the elastic wave filter involved in Embodiment 1 and Comparative Example 1.

[0033] Figure 17 It is Figure 16 The coordinate graph is magnified and shown near the frequency band of arrow A1 in the figure.

[0034] Figure 18 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-10.

[0035] Figure 19 This is a coordinate graph showing the relationship between Q and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-10.

[0036] Figure 20 This is a coordinate graph showing the relationship between Qr and aspect ratio (Wb1 / Wa1) of the elastic wave resonator involved in Embodiment 2.

[0037] Figure 21 This is a coordinate graph showing the relationship between Qa and aspect ratio (Wb1 / Wa1) of the elastic wave resonator involved in Embodiment 2.

[0038] Figure 22 This is a top view showing the structure of the elastic wave resonator involved in Embodiment 3.

[0039] Figure 23 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonator involved in Embodiment 3 and Embodiments 2-10.

[0040] Figure 24 This is a coordinate graph showing the relationship between Q and frequency of the elastic wave resonator involved in Embodiment 3 and Embodiments 2-10.

[0041] Figure 25 It is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonator involved in Example 4 according to each different ratio S / t.

[0042] Figure 26 It is a coordinate graph showing the relationship between Q and frequency of the elastic wave resonator involved in Example 4 according to each different ratio S / t.

[0043] Figure 27 This is a coordinate graph showing the relationship between the resonant resistance Zr and Qr of the elastic wave resonator involved in Embodiment 4 and the ratio S / t.

[0044] Figure 28 This is a coordinate graph showing the relationship between Qa and Qc of the elastic wave resonator involved in Embodiment 4 and the ratio S / t.

[0045] Figure 29 This is a coordinate graph showing the relationship between the Euler angles and the fractional bandwidth of the piezoelectric element using lithium niobate in the elastic wave resonator according to Embodiment 5-1.

[0046] Figure 30 This is a graph showing the relationship between the Euler angles and fractional bandwidth of the piezoelectric element using lithium tantalate in the elastic wave resonator of Embodiment 5-2.

[0047] Figure 31 This is a diagram showing the structure of the communication device according to the second embodiment. Detailed Implementation

[0048] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. However, the present disclosure is not limited to these embodiments. Furthermore, the embodiments described in this disclosure are exemplary, and partial substitutions or combinations of structures can be made between different embodiments. From the modified examples and the second embodiment onwards, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects resulting from the same structure are not mentioned repeatedly in each embodiment.

[0049] (First Embodiment)

[0050] Figure 1 This is a circuit diagram illustrating the elastic wave filter according to the first embodiment. Figure 1As shown, the elastic wave filter 50 according to the first embodiment includes a plurality of series arm resonators 61, 62, 63, 64, a plurality of parallel arm resonators 65, 66, 67, 68, and inductors 70A and 70B. At least one of the plurality of series arm resonators 61, 62, 63, 64 and the plurality of parallel arm resonators 65, 66, 67, 68 is a resonator utilizing a bulk wave with a thickness longitudinal vibration mode, i.e., a BAW (Bulk Acoustic Wave) element.

[0051] Multiple series-connected resonators 61, 62, 63, and 64 are connected in series in the signal path between input terminal 60A and output terminal 60B. Multiple parallel-connected resonators 65, 66, 67, and 68 are connected in parallel between the signal path between input terminal 60A and output terminal 60B and grounds 69A, 69B, 69C, and 69D. The elastic wave filter 50 according to the first embodiment is called a trapezoidal filter.

[0052] One terminal of each of the series-connected series-arm resonators 61, 62, 63, and 64 is electrically connected to the input terminal 60A, and the other terminal is electrically connected to the output terminal 60B. One terminal of the parallel-arm resonator 65 is electrically connected to the signal path connecting series-arm resonators 61 and 62, and the other terminal is electrically connected to ground 69A via inductor 70A. One terminal of the parallel-arm resonator 66 is electrically connected to the signal path connecting series-arm resonators 62 and 63, and the other terminal is electrically connected to ground 69B.

[0053] One terminal of the parallel arm resonator 67 is electrically connected to the signal path connecting the series arm resonator 63 and the series arm resonator 64, and the other terminal is electrically connected to ground 69C via inductor 70B. One terminal of the parallel arm resonator 68 is electrically connected to the signal path connecting the series arm resonator 64 and the output terminal 60B, and the other terminal is electrically connected to ground 69D.

[0054] Inductor 70A is connected in series in the signal path connecting the parallel arm resonator 65 to ground 69A. Inductor 70B is connected in series in the signal path connecting the parallel arm resonator 67 to ground 69C.

[0055] The elastic wave filter 50 is not limited to using inductors 70A and 70B as impedance elements; it may also include capacitors, etc. Furthermore, the impedance elements such as inductors 70A and 70B and capacitors are not limited to a structure connected to parallel arm resonators 65, 66, 67, and 68; they may also be connected to series arm resonators 61, 62, 63, and 64. Additionally, switching elements may be connected to the impedance elements such as inductors 70A and 70B and capacitors. In this case, the frequency of the filter characteristics of the elastic wave filter 50 can be varied according to the switching of the switching elements.

[0056] The series arm resonator 61 is composed of two resonators s1 that are divided in series. Series arm resonators 62, 63, and 64 are composed of four resonators s2, s3, and s4 that are divided in series, respectively. The number of divisions in each of the series arm resonators 61, 62, 63, and 64 is even. The number of divisions in each of the series arm resonators 61, 62, 63, and 64 is not limited to two or four; they may not be divided, or they may have three or more divisions.

[0057] Furthermore, the parallel arm resonator 65 is constructed by having two resonators p1 that are series-separated. Multiple parallel arm resonators 66, 67, and 68 are each constructed by having four resonators p2, p3, and p4 that are series-separated. The number of segments in each of the multiple parallel arm resonators 65, 66, 67, and 68 is even. The number of segments in each of the multiple parallel arm resonators 65, 66, 67, and 68 is not limited to two or four; they may not be segmented, or they may have three or five or more segments. Additionally, in the following description, "series-separated" refers to a structure in which multiple resonators with the same resonant frequency are connected in series.

[0058] The detailed structures of series arm resonators 61, 62, 63, and 64, and parallel arm resonators 65, 66, 67, and 68 will be discussed later. Figure 7 The following will describe this further. Furthermore, the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67, 68 respectively have the effect of being multiple resonators s1, s2, s3, s4, p1, p2, p3, p4 that are separated in series, which will also be discussed later. Figure 7 This will be discussed later.

[0059] In the elastic wave filter 50 of this embodiment, the structure and quantity of the plurality of series arm resonators 61, 62, 63, 64 and the plurality of parallel arm resonators 65, 66, 67, 68 can be appropriately changed according to the required filter characteristics. For example, the elastic wave filter 50 may also have a structure that includes at least one series arm resonator and at least one parallel arm resonator.

[0060] Figure 2This is a schematic cross-sectional view showing the structure of the elastic wave filter according to the first embodiment. Figure 3 This is a top view schematically showing the structure of the resonator chip in the elastic wave filter according to the first embodiment. Figure 4 This is a top view schematically showing the surface of the module substrate in the elastic wave filter according to the first embodiment. Figure 5 This is a schematic top view showing the inner layer of the module substrate in the elastic wave filter according to the first embodiment. Figure 6 This is a schematic top view of the back side of the module substrate in the elastic wave filter according to the first embodiment.

[0061] like Figure 2 As shown, the elastic wave filter 50 according to the first embodiment includes a resonator chip 51, a module substrate 52, bumps 55, and sealing resin 56. The resonator chip 51 is mounted on the module substrate 52 via the bumps 55. The resonator chip 51 includes... Figure 1 It is composed of multiple series arm resonators 61, 62, 63, 64 and multiple parallel arm resonators 65, 66, 67, 68, etc.

[0062] The module substrate 52 is a laminated substrate having multiple dielectric layers 53 and 54. The module substrate 52 can be, for example, a printed circuit board containing resin, or a ceramic substrate such as LTCC (Low Temperature Co-fired Ceramics) or HTCC (High Temperature Co-fired Ceramics). The module substrate 52 is not limited to two dielectric layers 53 and 54; it can have three or more dielectric layers, or it can be a single-layer substrate.

[0063] like Figure 3 As shown, the resonator chip 51 is mounted on the support member 13 with multiple series arm resonators 61, 62, 63, 64, multiple parallel arm resonators 65, 66, 67, 68, and multiple terminals (input terminal 60A, output terminal 60B, and ground terminals 69A, 69B, 69C, 69D). Input terminal 60A and output terminal 60B are located at opposite corners of the support member 13 in the inclined direction. Ground terminals 69A, 69B, 69C, and 69D are located at the periphery of the support member 13. The connection relationship between the multiple series arm resonators 61, 62, 63, 64, the multiple parallel arm resonators 65, 66, 67, 68, and the multiple terminals (input terminal 60A, output terminal 60B, and ground terminals 69A, 69B, 69C, 69D) is as follows: Figure 1 Similarly, repeated descriptions are omitted.

[0064] like Figure 4As shown, the module substrate 52 has multiple connection pads 57 and vias 58A. The multiple connection pads 57 are electrically connected to the input terminals 60A, output terminals 60B, and grounds 69A, 69B, 69C, and 69D of the resonator chip 51 via bumps 55. In addition, the multiple connection pads 57 are electrically connected to the inner layers and the back side of the module substrate 52 vias 58A.

[0065] like Figure 5 As shown, inductors 70A and 70B are formed on the inner layer of the module substrate 52. One end of inductors 70A and 70B is connected to a pad 57 and a via 58A (see reference). Figure 4 One end is electrically connected to the surface side of the module substrate 52, and the other end is electrically connected to the back side of the module substrate 52 through a via 58B.

[0066] like Figure 6 As shown, multiple connection pads 59 are provided on the back side of the module substrate 52. The elastic wave filter 50 is mounted to the high-frequency front-end circuit 101 (see reference 101) via the multiple connection pads 59. Figure 31 External devices such as )

[0067] Next, the detailed structure of the series arm resonator 61 will be described. Figure 7 This is a top view showing the structure of the series arm resonator in the elastic wave filter according to the first embodiment. Figure 8 yes Figure 7 Sectional view of VIII-VIII'. Figure 7 as well as Figure 8 The structure of the series arm resonator 61 among the multiple resonators in the resonator chip 51 is shown in an enlarged form. That is, Figure 7 as well as Figure 8 The structure of the series arm resonator 61 located on the input terminal 60A side is shown among a plurality of resonators.

[0068] Furthermore, in the following description, unless it is necessary to distinguish between the multiple series-arm resonators 61, 62, 63, 64 and the multiple parallel-arm resonators 65, 66, 67, 68 (multiple resonators s1, s2, s3, s4, p1, p2, p3, p4), they will only be referred to as elastic wave resonator 10. In addition, the structures of the other resonators are also similar to... Figure 7 as well as Figure 8 Similarly, the series arm resonator 61 shown is also for... Figure 7 as well as Figure 8 The description of the structure of the series arm resonator 61 can also be applied to the structure of other resonators.

[0069] First, the structure of one resonator s1 (elastic wave resonator 10) included in the series arm resonator 61 will be described. For example... Figure 7 as well as Figure 8 As shown, the elastic wave resonator 10 has a support member 13, a piezoelectric element 20, an upper electrode 31, a lower electrode 32, a frame electrode 33, and lead-out wirings 34 and 35. Figure 8 As shown, on the support member 13, the lower electrode 32, the piezoelectric body 20, the upper electrode 31, and the lead wires 34, 35 and the frame electrode 33 are stacked in sequence.

[0070] In the following description, the thickness direction of the piezoelectric material 20 is defined as the Z direction, the direction orthogonal to the Z direction is defined as the X direction, and the direction orthogonal to both the Z and X directions is defined as the Y direction. The X and Y directions are parallel to the surface (first main surface 20a) of the piezoelectric material 20. Furthermore, in the following description, the "top view" shows the arrangement when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric material 20 (Z direction).

[0071] The support member 13 is disposed opposite to the second main surface 20b of the piezoelectric body 20. The support member 13 includes a support substrate 11 and an intermediate layer 12. The support substrate 11 contains silicon (Si), quartz, or the like. The intermediate layer 12 is disposed between the support substrate 11 and the piezoelectric body 20. The intermediate layer 12 is formed of an insulating material such as silicon oxide. Alternatively, the support member 13 may not have an intermediate layer 12, and the piezoelectric body 20 may be disposed on the support substrate 11. That is, the piezoelectric body 20 is directly bonded to the support substrate 11 or bonded to the support substrate 11 via the intermediate layer 12 (insulating layer).

[0072] A recess 14 (cavity) is formed on the surface of the support member 13 (intermediate layer 12) opposite to the second main surface 20b of the piezoelectric body 20. The recess 14 is configured to overlap with the excitation region of the resonator formed by the piezoelectric body 20, the upper electrode 31, and the lower electrode 32 when viewed from above. As a result, the energy loss of the bulk wave during excitation is reduced, and good resonance characteristics can be obtained.

[0073] The piezoelectric material 20 is a flat plate having a first principal surface 20a and a second principal surface 20b opposite to the first principal surface 20a. The piezoelectric material 20 is a substrate containing a single crystal of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). The piezoelectric material 20 is not limited to this; aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), etc., can also be used. The thickness of the piezoelectric material 20 is not particularly limited, but is preferably 1 μm or less. Furthermore, the piezoelectric material 20 can also be a structure consisting of multiple layers of piezoelectric materials with different crystal orientations.

[0074] The upper electrode 31 is disposed above the piezoelectric body 20 (first main surface 20a). The lower electrode 32 is disposed below the piezoelectric body 20 (second main surface 20b). Figure 7 as well as Figure 8As shown, the upper electrode 31 and the lower electrode 32 overlap in the region where they overlap with the recess 14. In other words, in the region where they overlap with the recess 14, the piezoelectric element 20 is disposed between the upper electrode 31 and the lower electrode 32 in the Z direction. Thus, a volume wave propagates between the upper electrode 31 and the lower electrode 32. In the following description, the region where the upper electrode 31 and the lower electrode 32 overlap in top view will sometimes be described as the excitation region of the resonator.

[0075] Furthermore, the names such as upper electrode 31 and lower electrode 32 are only used to define the parts and do not limit the spatial arrangement and position of the BAW resonator. In addition, in top view, the upper electrode 31, lower electrode 32, and recess 14 are rectangular, but they are not limited to this and can also be other shapes such as circles.

[0076] The upper electrode 31 and the lower electrode 32 are formed of conductive materials such as aluminum (Al), platinum (Pt), gold (Au), copper (Cu), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), ruthenium (Ru), tantalum (Ta), and iridium (Ir), or alloys containing at least one of these materials. The upper electrode 31 and the lower electrode 32 may also be laminated films containing these materials. Furthermore, a close-bonding layer such as Ti or NiCr may be present between the upper electrode 31 and the support member 13 (intermediate layer 12).

[0077] In this embodiment, the series arm resonator 61 has a plurality of resonators s1 (elastic wave resonators 10) that are serially divided. The recess 14 is shared by the two resonators s1 constituting the series arm resonator 61. In other words, one recess 14 is provided for each of the two resonators s1.

[0078] The upper electrodes 31 of the two resonators s1 are respectively disposed on the first main surface 20a of the piezoelectric body 20 in the region overlapping with the recess 14, and are spaced apart in the X direction. The lower electrode 32 is shared by the two resonators s1 and is disposed on the second main surface 20b of the piezoelectric body 20 in the region overlapping with the recess 14. In other words, a region in the X direction of the lower electrode 32 ( Figure 8 The right-hand portion of the image is opposed to the upper electrode 31 of a resonator s1 via the piezoelectric element 20. Furthermore, another region in the X direction of the lower electrode 32 (…) Figure 8 The left part of the piezoelectric element 20 is opposed to the upper electrode 31 of another resonator s1.

[0079] Lead wires 34 and 35 are disposed on the same layer as the upper electrode 31 and connected to the upper electrode 31 in the X direction. More specifically, lead wire 34 is connected to the long side of the upper electrode 31 of one resonator s1 constituting the series arm resonator 61. Lead wire 35 is connected to the long side of the upper electrode 31 of the other resonator s1 constituting the series arm resonator 61. Lead wires 34 and 35, viewed from above, sandwich the upper electrode 31 and the lower electrode 32 and are opposed to each other in the X direction.

[0080] The lead wires 34 and 35 are formed of the same material as the upper electrode 31. However, the lead wires 34 and 35 may also be made of a different material than the upper electrode 31.

[0081] Furthermore, through-holes 15 are provided in the region overlapping with the recess 14 of the piezoelectric body 20. The through-holes 15 are provided for etching the sacrificial layer during the formation of the recess 14. The location and number of through-holes 15 are not limited. Figure 7 The example shown can be modified appropriately. Furthermore, the through hole 15 is sometimes omitted in the following embodiments and examples.

[0082] As described above, the elastic wave filter of this embodiment has an elastic wave resonator 10 that is a piezoelectric thin film resonator (FBAR). That is, a recess 14 (cavity) is formed in the portion of the support member 13 (intermediate layer 12) that overlaps with the excitation region, and the piezoelectric body 20, the upper electrode 31, and the lower electrode 32 have a film structure. However, it is not limited to this, the elastic wave resonator 10 may also be a solidly mounted resonator (SMR) obtained by stacking multiple low-impedance layers and high-impedance layers instead of the recess 14 (cavity).

[0083] In addition, Figure 1 as well as Figure 3 In the example shown, all the series arm resonators 61, 62, 63, and 64, and all the parallel arm resonators 65, 66, 67, and 68 are connected in series. However, this is not a limitation; at least the series arm resonator 64 closest to the output terminal 60B among the multiple series arm resonators 61, 62, 63, and 64 may be connected in series. Alternatively, at least the parallel arm resonator 68 closest to the output terminal 60B among the multiple parallel arm resonators 65, 66, 67, and 68 may be connected in series.

[0084] In this embodiment, since the multiple series-arm resonators 61, 62, 63, 64 and the multiple parallel-arm resonators 65, 66, 67, 68 are connected in series, the ratio (S / t) of the area S of the upper electrode 31 to the film thickness t of the piezoelectric element 20 increases when the impedance of the resonant circuit is high, thereby improving Q. Furthermore, the power density per unit area of ​​the multiple series-arm resonators 61, 62, 63, 64 and the multiple parallel-arm resonators 65, 66, 67, 68 decreases, improving power handling performance. More specifically, the area S of the upper electrode 31 refers to the area of ​​the excitation region where the upper electrode 31 and the lower electrode 32 overlap.

[0085] The multiple series-arm resonators 61, 62, 63, 64 and the multiple parallel-arm resonators 65, 66, 67, 68 are not limited to a structure in which they are separated in series; they can also be separated in parallel. In this case, especially when the impedance of the resonant circuit is low, by separating them in parallel, the region of the recess 14 is suppressed from becoming larger, thereby suppressing the decrease in the mechanical strength of each resonator.

[0086] Here, in the elastic wave filter 50 using BAW resonators, due to the nonlinear operation of the BAW resonators, the spectrum of the second harmonic is sometimes output. Furthermore, in the elastic wave filter 50, the second harmonic spectrum of each resonator is attenuated by the resonators on the output side and output from the output terminal 60B. However, the second harmonic spectrum of the resonator closest to the output terminal 60B (e.g., the series arm resonator 64) may be output from the output terminal 60B with almost no attenuation.

[0087] In this embodiment, the series arm resonator 64, located at least near the output terminal 60B, has four resonators s4 that are serially divided. Alternatively, the parallel arm resonator 68, located at least near the output terminal 60B, has four resonators p4 that are serially divided. Thus, in this embodiment, the subharmonic spectrum output from the output terminal 60B can be suppressed.

[0088] For example, when resonators are connected in series and divided into n segments (n is an integer), the energy density becomes n compared to resonators that are not divided. 2 One-third. Therefore, for example in Figure 7 , Figure 8 In the series arm resonator 61 shown, the nonlinear effect is reduced by 6 dB compared to the structure without segmentation.

[0089] In addition, such as Figure 7 , Figure 8As shown, the number of segments in the series arm resonator 61 is even, therefore the upper electrode 31 and lead-out wiring 34 of the input-side resonator s1 are formed on the same layer as the upper electrode 31 and lead-out wiring 35 of the output-side resonator s1. Therefore, compared to the case where the number of segments in the series arm resonator 61 is odd, there is no need for vias to connect the lower electrode 32 and the first main surface 20a side of the piezoelectric element 20, thus reducing manufacturing costs.

[0090] In addition, Figure 7 , Figure 8 In the diagram, arrows G1 and G2 indicate the voltage relationship of each resonator s1, arrows G3 and G4 indicate the polarization axis relationship of the piezoelectric element 20, and arrows G5 and G6 indicate the direction of displacement of the piezoelectric element 20. In this embodiment, the number of segments of the series arm resonator 61 is even, therefore one resonator s1 (e.g., Figure 7 , Figure 8 The voltage relationship between the right side and the polarization axis (refer to arrows G1, G3) and another resonator s1 (e.g. Figure 7 , Figure 8 The relationship between the voltage (on the left side) and the polarization axis (refer to arrows G2 and G4) shows an inverse relationship. Therefore, the second-order nonlinear signal is eliminated, and the second-order harmonic spectrum can be reduced.

[0091] The two resonators s1 of the series-connected resonator 61 are preferably of the same resonant frequency and the same impedance (the same braking capacitor). Thus, the nonlinear signals of the series-connected resonators s1 become the same magnitude, canceling out the second nonlinear signal.

[0092] Next, refer to Figure 8 as well as Figure 9 The structure of the upper electrode 31 and the frame electrode 33 will be described. Figure 9 This is a top view showing the structure of the upper electrode and the frame electrode. Figure 9 The structure of an elastic wave resonator 10 will be described in the following section. Furthermore, in... Figure 9 In the diagram, the first direction Da, indicated by the arrow, shows the direction in which the lead wire 34 (or lead wire 35) is connected to the upper electrode 31. In other words, the first direction Da is parallel to the surface of the piezoelectric body 20 (first main surface 20a), and is the direction in which the lead wire 34 and lead wire 35 sandwich the upper electrode 31 and the lower electrode 32 constituting an elastic wave resonator 10. The second direction Db is orthogonal to the first direction Da.

[0093] like Figure 8 as well as Figure 9As shown, in the elastic wave resonator 10 constituting the series arm resonator 61, the first direction Da is parallel to the X direction, and the second direction Db is parallel to the Y direction. However, in each of the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67, 68, the orientations of the first direction Da and the second direction Db are different.

[0094] For example, such as Figure 3 As shown, in the elastic wave resonators 10 (resonator s2) constituting the series arm resonator 62 and the elastic wave resonators 10 (resonator s3) constituting the series arm resonator 63, the first direction Da is parallel to the Y direction, and the second direction Db is parallel to the X direction. In the elastic wave resonator 10 (resonator s4) constituting the series arm resonator 64, the first direction Da is parallel to the X direction, and the second direction Db is parallel to the Y direction. Furthermore, in the elastic wave resonators 10 constituting the parallel arm resonators 65, 66, 67, and 68, the first direction Da is parallel to the X direction, and the second direction Db is parallel to the Y direction.

[0095] like Figure 8 As shown, the frame electrode 33 is connected to the upper electrode 31 and is disposed on the upper surface of the upper electrode 31 (the surface opposite to the piezoelectric element 20). Figure 9 As shown, the frame electrode 33 is configured in a frame shape along the outer periphery of the upper electrode 31. The frame electrode 33 is rectangular and has a first portion 33a extending in the first direction Da and a second portion 33b extending in the second direction Db.

[0096] In this embodiment, the external shape of the upper electrode 31 is defined by the frame electrode 33. Specifically, the length Wa1 of the upper electrode 31 in the first direction Da is equal to the maximum length of the frame electrode 33 in the first direction Da. More specifically, the length Wa1 of the upper electrode 31 in the first direction Da is equal to the maximum length in the first direction Da between the outer edges of two adjacent second portions 33b of the frame electrode 33. Furthermore, the length Wb1 of the upper electrode 31 in the second direction Db is equal to the maximum length in the second direction Db of the frame electrode 33. More specifically, the length Wb1 of the upper electrode 31 in the second direction Db is equal to the maximum length in the second direction Db between the outer edges of two adjacent first portions 33a of the frame electrode 33.

[0097] Furthermore, the width Wa2 of the second portion 33b extending along the second direction Db in the frame electrode 33 on the first direction Da is equal to the width Wb2 of the first portion 33a extending along the first direction Da in the frame electrode 33 on the second direction Db. In other words, the frame electrode 33 has equal widths Wa2 and Wb2 along the circumferential direction. However, this is not a limitation, and the widths Wa2 and Wb2 of the frame electrode 33 may be different.

[0098] like Figure 9 As shown, in the elastic wave resonator 10 constituting the series arm resonator 61, the upper electrode 31 and the frame electrode 33 are rectangular in shape with their long sides along a direction orthogonal to the connection direction (first direction Da) of the lead wires 34 and 35 (second direction Db). That is, the length Wb1 of the upper electrode 31 in the second direction Db is longer than the length Wa1 in the first direction Da. The ratio of the length Wa1 in the first direction Da to the length Wb1 in the second direction Db of the upper electrode 31, i.e., the aspect ratio (Wb1 / Wa1), is greater than 1.

[0099] like Figure 3 As shown, in the elastic wave filter 50 of this embodiment, the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 is greater than that of the parallel arm resonators 65, 66, 67, and 68. Specifically, the upper electrode 31 of each of the series arm resonators 61, 62, 63, and 64 is rectangular with its long side along the second direction Db. The upper electrode 31 of each of the parallel arm resonators 65, 66, 67, and 68 is circular with a length Wa1 in the first direction Da and a length Wb1 in the second direction Db equal.

[0100] Therefore, in the elastic wave filter 50 of this embodiment, compared to a structure in which the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 is the same as that of the parallel arm resonators 65, 66, 67, and 68, or a structure in which the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 is smaller than that of the parallel arm resonators 65, 66, 67, and 68, the filter loss can be suppressed.

[0101] Detailed structural examples and filter characteristics for the aspect ratios (Wb1 / Wa1) of series arm resonators 61, 62, 63, and 64 and the aspect ratios (Wb1 / Wa1) of parallel arm resonators 65, 66, 67, and 68 will be described later through Examples 1 to 5.

[0102] Furthermore, while the external shape of the upper electrode 31 has been described in this embodiment, the external shape of the lower electrode 32 can also be configured with the same structure. That is, Figure 8 as well as Figure 9 The length Wb1 of the lower electrode 32 in the second direction Db of the series arm resonator 61 shown is longer than the length Wa1 in the first direction Da. Furthermore, the aspect ratio (Wb1 / Wa1) of the lower electrode 32 of the series arm resonators 61, 62, 63, and 64 is greater than the aspect ratio (Wb1 / Wa1) of the lower electrode 32 of the parallel arm resonators 65, 66, 67, and 68. Furthermore, the structure in which the frame electrode 33 is disposed on the upper electrode 31 has been described, but this is a limitation. The frame electrode 33 may also be disposed on the lower electrode 32, or on both the upper and lower electrodes 31. In this case, for Figure 9 The description of the shapes of each part of the frame electrode 33 can also be applied to the frame electrode 33 provided on the lower electrode 32. Furthermore, in cases where the shapes of the upper electrode 31 and the lower electrode 32 are different (see [reference]...) Figure 7 , Figure 8 The shape of the upper electrode 31 can be changed to the shape of the region (excitation region) where the upper electrode 31 and the lower electrode 32 overlap.

[0103] exist Figure 9 In order to make the explanation easier to understand, the case where the frame electrode 33 is rectangular, that is, the outer shape of the upper electrode 31 is rectangular, is described. However, it is not limited to this, and the shapes of the frame electrode 33 and the upper electrode 31 can also be other shapes.

[0104] Figure 10 This is a top view showing the structure of the upper electrode and the frame electrode involved in the first modified example. (See attached image.) Figure 10 As shown, in the first modified example, the upper electrode 31 and the frame electrode 33A are elliptical in shape. More specifically, the upper electrode 31 and the frame electrode 33A are elliptical in shape with their major axis along a second direction Db perpendicular to the connection direction of the lead wires 34 and 35. That is, the length Wa1 of the upper electrode 31 is defined by the maximum length along the first direction Da of the elliptical shape. Furthermore, the length Wb1 of the upper electrode 31 is defined by the maximum length along the second direction Db of the elliptical shape.

[0105] Furthermore, in this modified example, the width Wa2 of the portion of the frame electrode 33A extending along the second direction Db (the portion intersecting the minor axis direction) in the first direction Da is also equal to the width Wb2 of the portion of the frame electrode 33A extending along the first direction Da (the portion intersecting the major axis direction) in the second direction Db.

[0106] Figure 11This is a top view showing the structure of the upper electrode and the frame electrode involved in the second modified example. (See attached image.) Figure 11 As shown, in the second modification, the upper electrode 31 and the frame electrode 33B are rectangular in shape with rounded corners. In other words, the first part 33Ba and the second part 33Bb of the frame electrode 33B are smoothly connected in a rounded shape. Alternatively, the upper electrode 31 and the frame electrode 33B may also be oblong in shape. The lengths Wa1 and Wb1 of the upper electrode 31, the aspect ratio (Wb1 / Wa1), and the widths Wa2 in the first direction Da and Wb2 in the second direction Db of the frame electrode 33B in the second modification are defined in the same way as in the first embodiment described above.

[0107] Figure 12 This is a top view showing the structure of the upper electrode and the frame electrode involved in the third modified example. Figure 12 As shown, in the third modification, the upper electrode 31 and the frame electrode 33C are polygonal. The first portion 33Ca, the second portion 33Cb, and the third portion 33Cc of the frame electrode 33C extend in directions inclined at an angle relative to the connection direction (first direction Da) of the lead wires 34 and 35. In this modification, the length Wa1 of the upper electrode 31 also becomes the maximum length of the frame electrode 33C in the first direction Da. Furthermore, the length Wb1 of the upper electrode 31 becomes the maximum length of the frame electrode 33C in the second direction Db.

[0108] In the third modification, the width Wa2 in the first direction Da of the frame electrode 33C is defined as the width Wa2 in the first direction Da of the portions extending along the second direction Db of the first portion 33Ca, the second portion 33Cb, and the third portion 33Cc (e.g., the second portion 33Cb with the smallest angle to the second direction Db). Furthermore, the width Wb2 in the second direction Db of the frame electrode 33C is defined as the width Wb2 in the second direction Db of the portions extending along the first direction Da of the first portion 33Ca, the second portion 33Cb, and the third portion 33Cc (e.g., the first portion 33Ca with the smallest angle to the first direction Da).

[0109] Figure 13 This is a cross-sectional view showing the structure of the upper electrode and the frame electrode involved in the fourth modified example. Figure 13As shown, in the fourth modification, the peripheral portion of the upper electrode 31 is separated from the piezoelectric body 20 by the insulating layer 22. In this case, the length Wb1 of the upper electrode 31 is defined by the portion of the upper electrode 31 that is in contact with the piezoelectric body 20 and has a frame electrode 33 (the portion where the piezoelectric body 20, the upper electrode 31, and the frame electrode 33 are stacked in sequence). The portion of the upper electrode 31 that is separated from the piezoelectric body 20 (the portion where the piezoelectric body 20, the insulating layer 22, the upper electrode 31, and the frame electrode 33 are stacked in sequence) is not included in the length Wb1. That is, the length Wb1 of the upper electrode 31 is the length of the portion of the upper electrode 31 that is in contact with the piezoelectric body 20 and has a frame electrode 33 in the second direction Db.

[0110] Furthermore, the width Wb2 in the second direction Db of the frame electrode 33 is also defined by the portion of the frame electrode 33 that overlaps the region where the upper electrode 31 and the piezoelectric body 20 are in contact (the portion where the piezoelectric body 20, the upper electrode 31, and the frame electrode 33 are stacked sequentially). The portion of the frame electrode 33 that overlaps the region where the upper electrode 31 and the piezoelectric body 20 are separated (the portion where the piezoelectric body 20, the insulating layer 22, the upper electrode 31, and the frame electrode 33 are stacked sequentially) is not included in the width Wb2. That is, the width Wb2 in the second direction Db of the frame electrode 33 is the length in the second direction Db of the portion of the frame electrode 33 that overlaps the region where the upper electrode 31 and the piezoelectric body 20 are in contact. Additionally, in Figure 13 The length Wb1 of the second direction Db of the upper electrode 31 and the width Wb2 of the second direction Db of the frame electrode 33 are described, but... Figure 13 The explanation can also be applied to the first direction, Da.

[0111] Figure 14 This is a top view showing the structure of the series arm resonator involved in the fifth variation. Figure 7 , Figure 8 The example shown illustrates a structure in which two resonators s1, separated in series, 61 are configured with a recess 14, but this is not a limitation. Figure 14 As shown, in the series arm resonator 61A involved in the fifth modification, each of the two resonators s1 that are series-separated has a recess 14a and 14b.

[0112] Two recesses 14a and 14b are spaced apart in the X direction. One resonator s1 of the series arm resonator 61A (e.g., ...) Figure 14 The upper electrode 31 (on the right side) is configured to overlap with a recess 14a. The other resonator s1 of the series arm resonator 61A (e.g., Figure 14 The upper electrode 31 (on the left side) overlaps with another recess 14b. The lower electrode 32 is continuously disposed across the two recesses 14a and 14b.

[0113] In the fifth modification, the portion of the lower electrode 32 located between the two recesses 14a and 14b is in contact with the support member 13 (intermediate layer 12). Therefore, in the fifth modification, the heat dissipation effect from the lower electrode 32 to the support member 13 is improved, thereby enhancing the power handling performance.

[0114] Next, the filter characteristics when the aspect ratios (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 and the parallel arm resonators 65, 66, 67, and 68 are different will be explained. Furthermore, for the elastic wave resonator 10 constituting the series arm resonators 61, 62, 63, and 64 and the parallel arm resonators 65, 66, 67, and 68, the resonator characteristics when the electrode shapes, such as the aspect ratio (Wb1 / Wa1), are different will be explained.

[0115] In the following embodiments and comparative examples, single crystals of lithium niobate were used as the material for piezoelectric body 20. Regarding the Euler angles (φ, θ, ψ) of the lithium niobate constituting piezoelectric body 20, (φ, θ, ψ) = (0°, 126°, 0°).

[0116] The upper electrode 31 is formed by sequentially stacking Ti / Pt / Ti / Al / Ti layers starting from the first main surface 20a of the piezoelectric body 20. The film thicknesses of Ti / Pt / Ti / Al / Ti are 4 / 11.3 or more and 39.3 or less, 14 / 100 / 4 nm, respectively. The lower electrode 32 is formed by sequentially stacking Ti / Pt / Ti / Al / Ti layers starting from the second main surface 20b of the piezoelectric body 20. The film thicknesses of Ti / Pt / Ti / Al / Ti are 4 / 11.3 or more and 39.3 or less, 14 / 100 / 4 nm, respectively.

[0117] The frame electrode 33 has Ti / Pt / Ti layers sequentially stacked on the surface of the upper electrode 31. The film thicknesses of Ti / Pt / Ti are 4 / 30 / 4 nm, respectively.

[0118] In the support member 13, the intermediate layer 12 is formed of silicon oxide (SiO2), and the support substrate 11 is formed of silicon (Si).

[0119] Furthermore, in Tables 1 to 3 of the various embodiments described below, and Figures 15 to 30 This includes deviations in filter characteristics caused by processing deviations in the manufacturing process, as well as deviations in resonator characteristics.

[0120] (Example 1)

[0121] In Example 1 and Comparative Example 1, the filter characteristics are explained when the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 is greater than the aspect ratio (Wb1 / Wa1) of the parallel arm resonators 65, 66, 67, and 68. Figure 15 This is a coordinate graph showing the filter characteristics of the elastic wave filter involved in Embodiment 1. Figure 16 This is a coordinate graph showing the filter characteristics of the elastic wave filter involved in Embodiment 1 and Comparative Example 1. Figure 17 It is Figure 16 The coordinate graph is magnified and shown near the frequency band of arrow A1. Table 1 shows structural examples of the resonators of the elastic wave filters involved in Embodiment 1 and Comparative Example 1.

[0122] In Embodiment 1, the upper electrode 31 of the series arm resonators 61, 62, 63, and 64 is rectangular, while the upper electrode 31 of the parallel arm resonators 65, 66, 67, and 68 is circular (see reference). Figure 3 ).

[0123] [Table 1]

[0124]

[0125] As shown in Table 1, the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is 4.0. The aspect ratio (Wb1 / Wa1) of the parallel arm resonators 65, 66, 67, and 68 (resonators p1, p2, p3, and p4) is 1.0.

[0126] The lengths Wa1, Wb1, and area S of the upper electrode 31 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) are different from each other. Furthermore, the lengths Wa1, Wb1, and area S of the upper electrode 31 of the parallel arm resonators 65, 66, 67, and 68 (resonators p1, p2, p3, and p4) are also different from each other.

[0127] The materials of the upper electrode 31, lower electrode 32, and frame electrode 33 are common to the series arm resonators 61, 62, 63, 64 (resonators s1, s2, s3, s4) and the parallel arm resonators 65, 66, 67, 68 (resonators p1, p2, p3, p4). However, the film thickness of Pt in the series arm resonators 61, 62, 63, 64 (resonators s1, s2, s3, s4) is thinner than that in the parallel arm resonators 65, 66, 67, 68 (resonators p1, p2, p3, p4). Furthermore, the film thickness of Pt in the series arm resonator 61 (resonator s1) on the input terminal 60A side is thicker than that in the series arm resonators 62, 63, 64 (resonators s2, s3, s4) on the output terminal 60B side. The film thickness of Pt of the parallel arm resonators 67 and 68 (resonators p3 and p4) on the output terminal 60B side is greater than the film thickness of Pt of the parallel arm resonators 65 and 66 (resonators p1 and p2) on the input terminal 60A side.

[0128] like Figure 15 As shown, the elastic wave filter 50 involved in Embodiment 1 has a loss of less than 2.1 dB in the frequency band indicated by arrow A1 (n79 frequency band: 4400MHz and above and 5000MHz and below).

[0129] Furthermore, the elastic wave filter 50 according to Embodiment 1 achieves attenuation of 25 dB or more in the frequency band indicated by arrow A2 (LTE band: 2690 MHz and below). Furthermore, the elastic wave filter 50 according to Embodiment 1 achieves attenuation of 30 dB or more in the frequency band indicated by arrow A3 (n77 band: 3300 MHz and above and 4200 MHz and below). Furthermore, the elastic wave filter 50 according to Embodiment 1 achieves attenuation of 25 dB or more in the frequency band indicated by arrow A4 (WiFi7 band: 5150 MHz and above and 7125 MHz and below).

[0130] As shown above, the elastic wave filter 50 according to Embodiment 1 has good filter characteristics.

[0131] Figure 16 as well as Figure 17 The aspect ratio of the elastic wave filter involved in Comparative Example 1 is reversed compared to that of Example 1. That is, in the elastic wave filter involved in Comparative Example 1, the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is 1.0. The aspect ratio (Wb1 / Wa1) of the parallel arm resonators 65, 66, 67, and 68 (resonators p1, p2, p3, and p4) is 4.0.

[0132] like Figure 16 as well as Figure 17 As shown, the elastic wave filter 50 of Embodiment 1 exhibits approximately 0.3 dB less loss in the n79 band indicated by arrow A1 compared to Comparative Example 1. Furthermore, Embodiment 1 and Comparative Example 1 show the same attenuation in each of the bands indicated by arrows A2 to A4 (LTE band, n77 band, WiFi 7 band).

[0133] Based on the above results, the elastic wave filter 50 involved in Embodiment 1 can reduce the loss in the filter characteristics by making the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 greater than the aspect ratio (Wb1 / Wa1) of the parallel arm resonators 65, 66, 67, and 68.

[0134] (Example 2)

[0135] In Example 2, for the elastic wave resonator 10 that constitutes series arm resonators 61, 62, 63, 64 and parallel arm resonators 65, 66, 67, 68, the resonator characteristics when the aspect ratio (Wb1 / Wa1) of the upper electrode 31 is different are explained.

[0136] Figure 18 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-10. Figure 19 This is a coordinate graph showing the relationship between Q and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-10. Figure 20 This is a coordinate graph showing the relationship between Qr and aspect ratio (Wb1 / Wa1) of the elastic wave resonator involved in Embodiment 2. Figure 21 This is a coordinate graph showing the relationship between Qa and aspect ratio (Wb1 / Wa1) of the elastic wave resonator involved in Embodiment 2.

[0137] Table 2 shows the relationship between the aspect ratio, length, area, and Q of the upper electrode of the elastic wave resonator involved in Example 2. (Table 2 and...) Figure 20 In the table, Qr represents the Q at the resonant frequency fr. Furthermore, in Table 2 and... Figure 21 In the diagram, Qa represents Q at the anti-resonant frequency fa.

[0138] [Table 2]

[0139]

[0140] As shown in Table 2, the elastic wave resonators 10 involved in Embodiments 2-1 to 2-13 have different aspect ratios (Wb1 / Wa1) ranging from 4.00 to 0.40. The upper electrode 31 in Embodiments 2-1 to 2-13 is rectangular (quadrilateral). Furthermore, the area S of the upper electrode 31 is fixed in Embodiments 2-1 to 2-13. That is, the impedance of the elastic wave resonators 10 involved in Embodiments 2-1 to 2-13 is a fixed value.

[0141] More specifically, the aspect ratio (Wb1 / Wa1) of Examples 2-1 to 2-9 is greater than 1.00. That is, the upper electrode 31 of Examples 2-1 to 2-9 is rectangular with its long side along the second direction Db. The aspect ratio (Wb1 / Wa1) of Example 2-10 is 1.00. That is, the upper electrode 31 of Example 2-10 is square. The aspect ratio (Wb1 / Wa1) of Examples 2-11 to 2-13 is less than 1.00. That is, the upper electrode 31 of Examples 2-11 to 2-13 is rectangular with its long side along the first direction Da.

[0142] like Figure 18As shown, the frequency characteristics of the impedance in Example 2-1 are approximately the same as those in Example 2-10. However, Example 2-1 (Wb1 / Wa1=4.0) has a larger aspect ratio than Example 2-10 (Wb1 / Wa1=1.0), therefore the absolute value of the impedance is slightly smaller.

[0143] like Figure 19 As shown, the frequency characteristics of Q in Embodiments 2-1 and 2-10 are different. Near the resonant frequency fr, Qr in Embodiment 2-1 (Wb1 / Wa1 = 4.0) is larger than Qr in Embodiment 2-10 (Wb1 / Wa1 = 1.0). On the other hand, near the anti-resonant frequency fa, Qa in Embodiment 2-10 is larger than Qa in Embodiment 2-1. Furthermore, Figure 18 , Figure 19 This includes deviations in resonator characteristics caused by processing errors during the manufacturing process.

[0144] like Figure 20 As shown, Qr increases with the aspect ratio (Wb1 / Wa1) of the upper electrode 31. Furthermore, Qr decreases sharply if the aspect ratio (Wb1 / Wa1) is 1.6 or less. That is, the slope of Qr in the region with an aspect ratio (Wb1 / Wa1) of 1.6 or less is greater than the slope of Qr in the region with an aspect ratio (Wb1 / Wa1) of 1.6 or more.

[0145] Here, in the ladder circuit elastic wave filter 50 (refer to...) Figure 1 , Figure 3 In the series arm resonators 61, 62, 63, and 64, the resonant frequencies fr are configured within the passband, while the anti-resonant frequency fa is configured in the attenuation band, which is higher than the passband. Therefore, in the elastic wave resonator 10 constituting the series arm resonators 61, 62, 63, and 64, Qr needs to be increased. According to Figure 20 The coordinate graph shown demonstrates that by setting the aspect ratio (Wb1 / Wa1) of the series arm resonators 61, 62, 63, and 64 to 1.6 or higher, the Qr at the resonant frequency is increased. Therefore, the elastic wave filter 50 can reduce its loss.

[0146] like Figure 21 As shown, when the aspect ratio (Wb1 / Wa1) of the upper electrode 31 is 1 (Examples 2-10), Qa shows a peak value. If the aspect ratio (Wb1 / Wa1) changes (i.e., if the aspect ratio (Wb1 / Wa1) becomes smaller or larger than 1), Qa shows a decreasing tendency.

[0147] Here, the anti-resonance frequency fa of the parallel arm resonators 65, 66, 67, and 68 is configured within the passband, while the resonant frequency fr is configured in the attenuation band, which is lower in frequency than the passband. Therefore, in the elastic wave resonator 10 constituting the parallel arm resonators 65, 66, 67, and 68, Qa needs to be increased. According to Figure 21 The coordinate graph shown demonstrates that by setting the aspect ratio (Wb1 / Wa1) of the parallel arm resonators 65, 66, 67, and 68 to 0.6 or higher and 1.8 or lower, Qa at the anti-resonant frequency increases. More specifically, by setting the aspect ratio (Wb1 / Wa1) to 0.6 or higher and 1.8 or lower, Qa becomes 230 or higher, achieving a value equivalent to the maximum value of Qa (Qa=236). Thus, the elastic wave filter 50 can reduce its loss.

[0148] (Example 3)

[0149] In Example 3, the characteristics of the elastic wave resonator 10A, which constitutes series arm resonators 61, 62, 63, 64 and parallel arm resonators 65, 66, 67, 68, are explained when the shape of the upper electrode 31 is different.

[0150] Figure 22 This is a top view showing the structure of the elastic wave resonator involved in Embodiment 3. Figure 23 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonator involved in Embodiment 3 and Embodiments 2-10. Figure 24 This is a coordinate graph showing the relationship between Q and frequency of the elastic wave resonator involved in Embodiment 3 and Embodiments 2-10.

[0151] like Figure 22 As shown, in the elastic wave resonator 10A according to Embodiment 3, the upper electrode 31 is circular. The length Wa1 of the upper electrode 31 in the first direction Da is the same as the length Wb1 of the upper electrode 31 in the second direction Db. The aspect ratio (Wb1 / Wa1) of the upper electrode 31 in Embodiment 3 is 1.0. Furthermore, the frame electrode 33 disposed on the outer periphery of the upper electrode 31 is also circular. The width of the frame electrode 33 is formed to a fixed size along the circumferential direction. That is, the width Wa2 of the frame electrode 33 in the first direction Da is the same as the width Wb2 in the second direction Db.

[0152] Compared with the first embodiment (see the first embodiment) Figure 7 , Figure 8 Similarly, the lower electrode 32 is shared by two adjacent elastic wave resonators 10A. The lower electrode 32 is an elongated oval shape with its long side along the first direction Da. A region of the lower electrode 32 in the first direction Da ( Figure 22The left-hand portion of the piezoelectric element 20 is positioned opposite the upper electrode 31 of an elastic wave resonator 10A. Furthermore, another region of the lower electrode 32 in the first direction Da ( Figure 22 The left part of the piezoelectric element 20 is positioned opposite the upper electrode 31 of another elastic wave resonator 10A.

[0153] exist Figure 23 as well as Figure 24 In order to compare with the elastic wave resonator 10A according to Embodiment 3, the resonator characteristics of Embodiments 2-10 are shown. The upper electrode 31 in Embodiments 2-10 is rectangular (quadrilateral). The aspect ratio (Wb1 / Wa1) of the upper electrode 31 in Embodiments 2-10 is 1.0; in this case, the upper electrode 31 is square. Furthermore, Figure 23 as well as Figure 24 This includes deviations in resonator characteristics caused by processing errors during the manufacturing process.

[0154] like Figure 23 As shown, the elastic wave resonator 10A involved in Embodiment 3 has approximately the same impedance frequency characteristics as that in Embodiments 2-10. Figure 24 As shown, the elastic wave resonator 10A according to Embodiment 3 exhibits a larger Q value in the frequency band between the anti-resonance frequency and the resonant frequency compared to Embodiments 2-10. That is, the elastic wave resonator 10A according to Embodiment 3 has larger Qr and Qa compared to Embodiments 2-10. Therefore, the elastic wave filter 50 using the elastic wave resonator 10A according to Embodiment 3 can reduce losses.

[0155] In Embodiment 3, the upper electrode 31 is circular, and the frame electrode 33 has the same width throughout the circumference. That is, the rectangular frame electrode 33 of Embodiments 2-10 has a structure with corners, and the width at the corners is formed to have a width different from the other parts. On the other hand, Embodiment 3 does not have corners. Therefore, the elastic wave resonator 10A according to Embodiment 3 can effectively suppress the leakage of bulk wave energy to the outside of the excitation region for various modes of standing waves in the planar direction residing in the region surrounded by the frame electrode 33, including the mode of standing waves containing the first direction Da, and the mode of standing waves in a direction inclined relative to the first direction Da (e.g., a direction inclined at 45°).

[0156] In addition, Figure 22 The example given is that the upper electrode 31 is circular, but it is not limited to this; the upper electrode 31 can also be elliptical.

[0157] (Example 4)

[0158] In Embodiment 4, the resonator characteristics of the elastic wave resonator 10 are described when the aspect ratio (Wb1 / Wa1) of the upper electrode 31 is fixed and the area S of the upper electrode 31 is different from S / t. Here, more specifically, the area S of the upper electrode 31 represents the area of ​​the region where the upper electrode 31 and the lower electrode 32 overlap.

[0159] Figure 25 It is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonator involved in Example 4 according to each different ratio S / t. Figure 26 It is a coordinate graph showing the relationship between Q and frequency of the elastic wave resonator involved in Example 4 according to each different ratio S / t. Figure 27 This is a coordinate graph showing the relationship between the resonant resistance Zr and Qr of the elastic wave resonator involved in Embodiment 4 and the ratio S / t. Figure 28 This is a coordinate graph showing the relationship between Qa and Qc of the elastic wave resonator involved in Embodiment 4 and the ratio S / t. Additionally, Figure 25 , Figure 26 This includes deviations in resonator characteristics caused by processing errors during the manufacturing process.

[0160] Table 3 shows the area of ​​the upper electrode, the thickness of the piezoelectric element, and the relationship between the ratio S / t and the resonant resistance Zr and Q of the elastic wave resonator involved in Example 4. In Table 3, Qr represents Q at the resonant frequency fr, and Qa represents Q at the anti-resonant frequency fa. Furthermore, Qc is Q at the frequency fc, which is the center between the resonant frequency fr and the anti-resonant frequency fa.

[0161] [Table 3]

[0162]

[0163] As shown in Table 3, in Examples 4-1 to 4-11, the film thickness t of the piezoelectric body 20 was fixed, and the area S of the upper electrode 31 was increased from 500 μm. 2 Up to 16000μm 2 However, the differences are as follows. In Examples 4-1 and 4-2, when the area of ​​the upper electrode 31 is set to S and the film thickness of the piezoelectric body 20 is set to t, the ratio of area S to film thickness t, S / t, is less than 2000 μm. In Examples 4-3 to 4-11, the ratio of area S / t of the upper electrode 31 to film thickness of the piezoelectric body 20 is greater than 2000 μm. The stacked structure and film thickness of the upper electrode 31 and the frame electrode 33 are the same as in Example 2 described above.

[0164] exist Figure 25 as well as Figure 26Table 3 shows the frequency characteristics of the impedance of the elastic wave resonator 10 involved in Embodiments 4-3, 4-5, 4-7, 4-9, and 4-11 of Embodiments 4-1 to 4-11. Figure 25 As shown, as the area S of the upper electrode 31 increases, that is, as the ratio S / t increases, the impedance decreases.

[0165] like Figure 26 As shown, the frequency response of Q exhibits different tendencies for each different ratio S / t. Near the resonant frequency fr, the smaller the ratio S / t becomes, the larger Q becomes. Near the anti-resonant frequency fa, the larger the ratio S / t becomes, the larger Q becomes.

[0166] Figure 27 The horizontal axis of the coordinate graph shown is the ratio S / t of the area S of the upper electrode 31 to the film thickness t of the piezoelectric body 20. The vertical axis represents the resonant resistance Zr of the elastic wave resonator 10, which is related to the series resistance (vertical axis on the right), and Qr at the resonant frequency fr (vertical axis on the left). Figure 28 The horizontal axis of the coordinate graph shown represents the ratio S / t, and the vertical axis represents Qc at the central frequency fc and Qa at the anti-resonant frequency fa.

[0167] like Figure 27 As shown, if the ratio S / t increases, the resonant resistance Zr decreases. If the ratio S / t is less than 2000 μm (Examples 4-1, 4-2), the resonant resistance Zr increases sharply. Figure 27 As shown, Qr exhibits a peak value when the ratio S / t is S / t = 2028 μm (Example 4-3). If the ratio S / t changes (becomes less than 2000 μm or becomes greater than 2000 μm), Qr tends to decrease.

[0168] like Figure 28 As shown, Qa increases as the ratio S / t increases. Furthermore, Qc exhibits a peak at a ratio S / t of S / t = 8114 μm (Examples 4-7). Qc tends to decrease as the ratio S / t changes. In particular, Qc decreases sharply if the ratio S / t becomes less than 2000 μm.

[0169] Here, the resonant frequencies fr of the series arm resonators 61, 62, 63, and 64 are located within the passband, while the anti-resonant frequency fa is located in the attenuation band, which is higher than the passband. The center frequency fc is near the high-frequency end of the passband. Therefore, in the series arm resonators 61, 62, 63, and 64, it is required to reduce the resistance component near the resonant frequency fr and increase the Qc at the center frequency fc.

[0170] The anti-resonance frequency fa of the parallel arm resonators 65, 66, 67, and 68 is located within the passband, while the resonant frequency fr is located in the attenuation band, which is lower than the passband. The center frequency fc is near the low-frequency end of the passband. Therefore, in the parallel arm resonators 65, 66, 67, and 68, it is necessary to increase Qa at the anti-resonance frequency fa and Qc at the center frequency fc.

[0171] according to Figure 27 , Figure 28 As shown, in the elastic wave resonator 10 constituting the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67, 68, by setting the ratio S / t of the area S of the upper electrode 31 to the film thickness t of the piezoelectric element 20 to 2000 μm or more, it is possible to suppress the increase of the resonant resistance Zr, and to increase Qa at the anti-resonant frequency fa and Qc at the center frequency fc. As a result, the elastic wave filter 50 can reduce its losses.

[0172] (Example 5)

[0173] In Example 5, the fractional bandwidth ΔfR and piezoelectric constant are explained when the Euler angles of the lithium niobate or lithium tantalate used in the piezoelectric body 20 are different. Figure 29 This is a graph showing the relationship between the Euler angles and the fractional bandwidth of the piezoelectric element using lithium niobate in the elastic wave resonator according to Embodiment 5-1. In the elastic wave resonator 10 according to Embodiment 5-1, lithium niobate is used as the piezoelectric element 20.

[0174] In addition, regarding Figure 29 The fractional bandwidth ΔfR shown is represented by ΔfR = (fa-fr) / fr when the resonant frequency of the elastic wave resonator 10 is set as fr, the anti-resonant frequency is set as fa, and the frequency difference between the resonant frequency and the anti-resonant frequency is set as (fa-fr).

[0175] Figure 29 The horizontal axis of the coordinate graph shown represents the Euler angle θ of lithium niobate. For example... Figure 29 As indicated by arrow B1, the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element 20 are preferably set to the range of (φ, θ, ψ) = (0°, 107 to 140°, 0°). Therefore, the elastic wave resonator 10 according to Embodiment 5-1 can achieve a wide bandwidth of 10% or more.

[0176] In addition, such as Figure 29As indicated by arrow B2, it is preferable to set the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric body 20 to the range of (φ, θ, ψ) = (0°, 123 to 139°, 0°). Within this range, the fractional bandwidth ΔfR of the transverse wave (planar direction) becomes less than 0.5%, and the elastic wave resonator 10 according to Embodiment 5-1 can reduce unwanted waves caused by the transverse wave.

[0177] Figure 30 This is a graph showing the relationship between the Euler angles and the fractional bandwidth of the piezoelectric element using lithium tantalate in the elastic wave resonator according to Embodiment 5-2. In the elastic wave resonator 10 according to Embodiment 5-2, lithium tantalate is used as the piezoelectric element 20.

[0178] Figure 30 The horizontal axis of the coordinate graph shown represents the Euler angle θ of lithium tantalate. For example... Figure 30 As indicated by arrow C1, it is preferable to set the Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element 20 to the range of (φ, θ, ψ) = (0°, 101 to 134°, 0°). Therefore, the elastic wave resonator 10 according to Embodiment 5-2 can achieve a wideband with a fractional bandwidth ΔfR of 3% or more.

[0179] In addition, such as Figure 30 As indicated by arrow C2, it is preferable to set the Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element 20 to the range of (φ, θ, ψ) = (0°, 123 to 139°, 0°). Within this range, the fractional bandwidth ΔfR of the transverse wave (planar direction) becomes less than 0.5%, and the elastic wave resonator 10 according to Embodiment 5-2 can reduce unwanted waves caused by the transverse wave.

[0180] In Example 5-1, when lithium niobate (longitudinal wave) with a thickness longitudinal vibration mode was used as the piezoelectric body 20, the piezoelectric constant e with Euler angles (φ, θ, ψ) of (φ, θ, ψ) = (0°, 107~140°, 0°) was used. 33 The value is 3.8 or higher. Furthermore, in Example 5-2, when lithium tantalate (longitudinal wave) with a thickness longitudinal vibration mode was used as the piezoelectric element 20, the piezoelectric constant e with Euler angles (φ, θ, ψ) of (φ, θ, ψ) = (0°, 101~134°, 0°) is... 33 The value is 2.5 or higher. Here, unlike Examples 5-1 and 5-2, in the elastic wave resonator 10 where aluminum nitride (AlN) is used as the material for the piezoelectric element 20, generally, the longitudinal wave is used as the fundamental mode, and the longitudinal piezoelectric constant e is... 33 The value is 1.515. Therefore, the longitudinal piezoelectric constant e is relative to the elastic wave resonator 10 using AlN. 33 The longitudinal piezoelectric constant e of the elastic wave resonator 10 using lithium niobate or lithium tantalate is...33 It is large enough to obtain a wideband resonator.

[0181] The structures of the above embodiments can be appropriately combined. Furthermore, the specific structures and values ​​of each embodiment (e.g., the lengths Wa1 and Wb1 of the upper electrode 31, the widths Wa2 and Wb2 of the frame electrode 33, the area S of each electrode, etc.) are merely examples and are not limited thereto.

[0182] (Second Implementation)

[0183] Figure 31 This diagram illustrates the structure of the communication device according to the second embodiment. The communication device 100 according to the second embodiment is, for example, a portable terminal such as a mobile phone, smartphone, or tablet computer, or a personal computer with communication capabilities. Alternatively, the communication device 100 may also be a backhaul communication device that performs communication between base stations and communication between a base station and a core network.

[0184] like Figure 31 As shown, the communication device 100 includes a high-frequency front-end circuit 101, an antenna 102, an RF-IC (Radio Frequency Integrated Circuit) 104, and a BB-IC (Baseband Integrated Circuit) 105.

[0185] The BB-IC105 forms the baseband signal processing circuit. The BB-IC105 supplies the baseband signal to the RF-IC104. The RF-IC104 performs high-frequency signal processing for transmitting and receiving signals.

[0186] The high-frequency front-end circuit 101 is connected between the antenna 102 and the RF-IC 104. In the communication device 100, high-frequency transmission signals can be output from the high-frequency front-end circuit 101 to the antenna 102, and high-frequency reception signals from the antenna 102 can be received by the high-frequency front-end circuit 101.

[0187] Specifically, the high-frequency front-end circuit 101 includes a switch SW, power amplifiers 111a and 111b, matching circuits 112a and 112b, a transmit filter 113a and 113b, a multiplexer 114, matching circuits 115a and 115b, and low-noise amplifiers 116a and 116b.

[0188] When transmitting a high-frequency signal, switch SW switches to either transmit filter 113a or transmit filter 113b. The high-frequency transmit signal output from RF-IC104 is amplified by power amplifier 111a or power amplifier 111b and then input to transmit filter 113a or transmit filter 113b through matching circuits 112a and 112b.

[0189] The frequency band of transmit filter 113a is, for example, n77 of the 5G NR (New Radio) standard. The frequency range of 5G NR n77 is above 3.3 GHz and below 4.2 GHz. The frequency band of transmit filter 113b is, for example, n79 of the 5G NR standard. The frequency range of 5G NR n79 is above 4.4 GHz and below 5.0 GHz.

[0190] The high-frequency transmission signal that has passed through transmission filter 113a or transmission filter 113b is supplied to antenna 102.

[0191] When receiving high-frequency signals, switch SW switches to the multiplexer 114. Multiplexer 114 includes receive filters 117a and 117b, and a matching circuit 118. In multiplexer 114, the input terminals of the multiple receive filters 117a and 117b are electrically connected via the matching circuit 118. The frequency band of receive filter 117a is, for example, n77 of the 5G NR standard. The frequency band of receive filter 117b is, for example, n79 of the 5G NR standard.

[0192] The received signal from antenna 102 passes through matching circuit 118 and then through receive filter 117a or receive filter 117b. The high-frequency received signal that has passed through receive filter 117a or receive filter 117b is then transmitted to RF-IC 104 through matching circuits 115a, 115b and low-noise amplifier 116a or low-noise amplifier 116b.

[0193] In the communication device 100 of this embodiment, at least one of the transmitting filters 113a and 113b is the aforementioned elastic wave filter 50. Furthermore, in the multiplexer 114, at least one of the receiving filters 117a and 117b is the aforementioned elastic wave filter 50. The high-frequency front-end circuit 101 includes at least one of the transmitting filters 113a and 113b, and at least one of the receiving filters 117a and 117b of the multiplexer 114. Furthermore, the communication device 100 includes the high-frequency front-end circuit 101.

[0194] in addition, Figure 31 The structure of the communication device 100 shown is merely schematic and can be modified accordingly. Furthermore, the frequency bands of the transmitting filters 113a and 113b and the receiving filters 117a and 117b are just one example, and other communication standards can also be applied. The structure of the multiplexer 114 is also just one example and can be modified accordingly. For example, the multiple filters of the multiplexer 114 can have their output terminals electrically connected to each other depending on the device on which they are mounted.

[0195] Furthermore, the above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the interpretation of the invention. The present invention can be modified / improved without departing from its spirit, and equivalents are also included in the present invention.

[0196] Alternatively, this disclosure can also adopt the following structure.

[0197] (1) An elastic wave filter, which comprises multiple elastic wave resonators utilizing the longitudinal vibration mode of a body wave,

[0198] It includes a series arm resonator and a parallel arm resonator constructed using the aforementioned elastic wave resonator.

[0199] The series arm resonator and the parallel arm resonator each have:

[0200] piezoelectric elements;

[0201] The upper electrode is disposed on the piezoelectric body;

[0202] The lower electrode is disposed below the piezoelectric element; and

[0203] Lead-out wiring is connected to at least one of the upper electrode and the lower electrode, and the upper electrode and the lower electrode are sandwiched and opposed in the first direction when viewed from above.

[0204] When the ratio of the length (Wa1) of at least one of the upper electrode and the lower electrode in the first direction to the length (Wb1) in the second direction perpendicular to the first direction is set as the aspect ratio (Wb1 / Wa1),

[0205] The aspect ratio (Wb1 / Wa1) of the series arm resonator is greater than that of the parallel arm resonator.

[0206] (2) According to the elastic wave filter described in (1), where,

[0207] The aspect ratio (Wb1 / Wa1) of the series arm resonator is 1.6 or higher.

[0208] (3) The elastic wave filter described in (1) or (2), wherein,

[0209] The aspect ratio (Wb1 / Wa1) of the parallel arm resonator is greater than 0.6 and less than 1.8.

[0210] (4) An elastic wave filter according to any one of (1) to (3), wherein,

[0211] At least one of the upper electrode and the lower electrode of the parallel arm resonator is circular or elliptical.

[0212] (5) An elastic wave filter according to any one of (1) to (4), wherein,

[0213] The elastic wave filter has an input terminal, an output terminal, a plurality of series-arm resonators connected between the input terminal and the output terminal, and a plurality of parallel-arm resonators.

[0214] The series arm resonator closest to the output terminal among the plurality of series arm resonators is configured by being divided in series, and the number of divisions of the series arm resonator is even.

[0215] (6) An elastic wave filter according to any one of (1) to (5), wherein,

[0216] The elastic wave filter has an input terminal, an output terminal, a plurality of series-arm resonators connected between the input terminal and the output terminal, and a plurality of parallel-arm resonators.

[0217] The parallel arm resonator closest to the output terminal among the plurality of parallel arm resonators is configured by being divided in series, and the number of divisions of the parallel arm resonator is even.

[0218] (7) An elastic wave filter according to any one of (1) to (6), wherein,

[0219] The ratio (S / t) of the area (S) of the region where the upper electrode and the lower electrode overlap to the film thickness (t) of the piezoelectric material is 2000 μm or more.

[0220] (8) An elastic wave filter according to any one of (1) to (7), wherein,

[0221] The piezoelectric element comprises lithium niobate or lithium tantalate.

[0222] (9) An elastic wave filter according to any one of (1) to (7), wherein,

[0223] The piezoelectric element comprises lithium niobate.

[0224] The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 107 to 140°, 0°).

[0225] (10) An elastic wave filter according to any one of (1) to (7), wherein,

[0226] The piezoelectric element comprises lithium niobate.

[0227] The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 123 to 139°, 0°).

[0228] (11) An elastic wave filter according to any one of (1) to (7), wherein,

[0229] The piezoelectric element comprises lithium tantalate.

[0230] The Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 101 to 134°, 0°).

[0231] (12) An elastic wave filter according to any one of (1) to (7), wherein,

[0232] The piezoelectric element comprises lithium tantalate.

[0233] The Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 123 to 134°, 0°).

[0234] (13) A multiplexer having a plurality of filters including the elastic wave filter described in any one of (1) to (12),

[0235] The input and output terminals of each of the plurality of filters are electrically connected to each other.

[0236] (14) A high-frequency front-end circuit having an elastic wave filter described in any one of (1) to (12).

[0237] (15) A high-frequency front-end circuit having the multiplexer described in (13).

[0238] (16) A communication device having the high-frequency front-end circuit described in (14) or (15).

[0239] Explanation of reference numerals in the attached figures

[0240] 10, 10A: Elastic wave resonator

[0241] 11: Support base plate

[0242] 12: Intermediate layer

[0243] 13: Supporting components

[0244] 14, 14a, 14b: concave part

[0245] 20: Piezoelectric element

[0246] 20a: 1st main side

[0247] 20b: Second Main Page

[0248] 31: Upper electrode

[0249] 32: Lower electrode

[0250] 33, 33A, 33B, 33C: Frame electrodes

[0251] 33a, 33Ba, 33Ca: Part 1

[0252] 33b, 33Bb, 33Cb: Part 2

[0253] 33Cc: Part 3

[0254] 34, 35: Outgoing wiring

[0255] 50: Elastic wave filter

[0256] 51: Resonator Chip

[0257] 52: Module baseboard

[0258] 53, 54: Dielectric layer

[0259] 55: Bump

[0260] 56: Sealing resin

[0261] 61, 61A, 62, 63, 64: Series arm resonators

[0262] 65, 66, 67, 68: Parallel arm resonators

[0263] 100: Communication device

[0264] 101: High-frequency front-end circuit

[0265] Wa1, Wb1: Length

[0266] Wa2, Wb2: Width.

Claims

1. An elastic wave filter comprising multiple elastic wave resonators utilizing the longitudinal vibration mode of a body wave. It includes a series arm resonator and a parallel arm resonator constructed using the aforementioned elastic wave resonator. The series arm resonator and the parallel arm resonator each have: piezoelectric elements; The upper electrode is disposed on the piezoelectric body; The lower electrode is disposed below the piezoelectric element; and Lead-out wiring is connected to at least one of the upper electrode and the lower electrode, and the upper electrode and the lower electrode are sandwiched and opposed in the first direction when viewed from above. When the ratio of the length Wa1 of at least one of the upper electrode and the lower electrode in the first direction to the length Wb1 in the second direction perpendicular to the first direction is set as the aspect ratio Wb1 / Wa1, The aspect ratio Wb1 / Wa1 of the series arm resonator is greater than that of the parallel arm resonator.

2. The elastic wave filter according to claim 1, wherein, The aspect ratio Wb1 / Wa1 of the series arm resonator is 1.6 or higher.

3. The elastic wave filter according to claim 1 or 2, wherein, The aspect ratio Wb1 / Wa1 of the parallel arm resonator is greater than 0.6 and less than 1.

8.

4. The elastic wave filter according to any one of claims 1 to 3, wherein, At least one of the upper electrode and the lower electrode of the parallel arm resonator is circular or elliptical.

5. The elastic wave filter according to any one of claims 1 to 4, wherein, The elastic wave filter has an input terminal, an output terminal, a plurality of series-arm resonators connected between the input terminal and the output terminal, and a plurality of parallel-arm resonators. The series arm resonator closest to the output terminal among the plurality of series arm resonators is divided in series, and the number of divisions of the series arm resonator is even.

6. The elastic wave filter according to any one of claims 1 to 5, wherein, The elastic wave filter has an input terminal, an output terminal, a plurality of series-arm resonators connected between the input terminal and the output terminal, and a plurality of parallel-arm resonators. The parallel arm resonator closest to the output terminal among the plurality of parallel arm resonators is configured by being divided in series, and the number of divisions of the parallel arm resonator is even.

7. The elastic wave filter according to any one of claims 1 to 6, wherein, The ratio S / t of the area where the upper electrode and the lower electrode overlap to the film thickness t of the piezoelectric material is 2000 μm or more.

8. The elastic wave filter according to any one of claims 1 to 7, wherein, The piezoelectric element comprises lithium niobate or lithium tantalate.

9. The elastic wave filter according to any one of claims 1 to 7, wherein, The piezoelectric element comprises lithium niobate. The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 107 to 140°, 0°).

10. The elastic wave filter according to any one of claims 1 to 7, wherein, The piezoelectric element comprises lithium niobate. The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 123 to 139°, 0°).

11. The elastic wave filter according to any one of claims 1 to 7, wherein, The piezoelectric element comprises lithium tantalate. The Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 101 to 134°, 0°).

12. The elastic wave filter according to any one of claims 1 to 7, wherein, The piezoelectric element comprises lithium tantalate. The Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 123 to 134°, 0°).

13. A multiplexer having a plurality of filters comprising an elastic wave filter according to any one of claims 1 to 12, The input and output terminals of each of the plurality of filters are electrically connected to each other.

14. A high-frequency front-end circuit comprising the elastic wave filter according to any one of claims 1 to 12.

15. A high-frequency front-end circuit comprising the multiplexer of claim 13.

16. A communication device comprising the high-frequency front-end circuit as described in claim 14 or 15.

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