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 utilizing bulk waves, the plurality of elastic wave resonators each having a piezoelectric body, an upper electrode provided on the piezoelectric body, a lower electrode provided under the piezoelectric body, and a frame electrode provided in a frame shape along an outer periphery of at least one of the upper electrode and the lower electrode, the frame electrode of at least one of the plurality of elastic wave resonators including a plurality of first portions and a plurality of second portions having a width or a height larger than the plurality of first portions, the plurality of first portions and the plurality of second portions being alternately arranged in a direction along the outer periphery.

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 an elastic wave resonator in which a weighted portion with a mass per unit area greater than that of the central portion is provided along the long side of the upper electrode (in Patent Document 1, 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 elastic wave resonators having frame electrodes (emphasized portions in Patent Document 1) arranged along the outer periphery of the electrodes, there is a need to improve the filter characteristics.

[0008] The purpose of this invention is to provide an elastic wave filter, multiplexer, high-frequency front-end circuit, and communication device that can improve filter characteristics.

[0009] Technical solutions for solving the problem

[0010] One proposed solution involves an elastic wave filter comprising multiple elastic wave resonators utilizing body waves. Each of the multiple elastic wave resonators includes: a piezoelectric body; an upper electrode disposed above the piezoelectric body; a lower electrode disposed below the piezoelectric body; and a frame electrode configured in a frame shape along the outer periphery of at least one of the upper and lower electrodes. The frame electrode of at least one of the multiple elastic wave resonators includes multiple first portions and multiple second portions having a width or height larger than the multiple first portions. The multiple first portions and the multiple second portions are alternately arranged in a direction along the outer periphery.

[0011] One proposed solution involves an elastic wave filter comprising multiple elastic wave resonators utilizing body waves. Each of the multiple elastic wave resonators includes: a piezoelectric body; an upper electrode disposed above the piezoelectric body; a lower electrode disposed below the piezoelectric body; and a frame electrode disposed along the outer periphery of at least one of the upper and lower electrodes for adding mass. The frame electrode of the elastic wave resonator having a resonant frequency higher than the low-frequency end of the passband includes multiple first portions and multiple second portions having a width or height greater than the first portions. The multiple first portions and the multiple second portions are alternately arranged along the outer periphery.

[0012] One solution 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.

[0013] One of the solutions involves a high-frequency front-end circuit that includes the aforementioned elastic wave filter.

[0014] One of the solutions involves a high-frequency front-end circuit that includes the aforementioned multiplexer.

[0015] One of the solutions involves a communication device that has the aforementioned high-frequency front-end circuit.

[0016] Invention Effects

[0017] 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

[0018] Figure 1 This is a circuit diagram showing the elastic wave filter according to the first embodiment.

[0019] Figure 2 This is a schematic cross-sectional view illustrating the structure of the elastic wave filter according to the first embodiment.

[0020] Figure 3 This is a top view schematically illustrating the structure of the resonator chip in the elastic wave filter according to the first embodiment.

[0021] 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.

[0022] 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.

[0023] Figure 6This is a schematic top view showing the back of the module substrate in the elastic wave filter according to the first embodiment.

[0024] Figure 7 This is a top view schematically illustrating the structure of the series arm resonator in the elastic wave filter according to the first embodiment.

[0025] Figure 8 yes Figure 7 Sectional view of VIII-VIII'.

[0026] Figure 9 This is a top view showing the structure of the upper electrode and the frame electrode.

[0027] Figure 10 It is Figure 9 A top view showing an enlarged portion of the upper electrode and frame electrode.

[0028] Figure 11 This is a top view showing the structure of the upper electrode and frame electrode involved in the first modified example.

[0029] Figure 12 This is a top view showing the structure of the upper electrode and the frame electrode involved in the second modified example.

[0030] Figure 13 This is a top view showing the structure of the upper electrode and the frame electrode involved in the third modified example.

[0031] Figure 14 This is a cross-sectional view showing the structure of the upper electrode and the frame electrode involved in the fourth modified example.

[0032] Figure 15 This is a top view showing the structure of the series arm resonator involved in the fifth variation.

[0033] Figure 16 This is a top view showing the structure of the upper electrode and frame electrode involved in the sixth modified example.

[0034] Figure 17 yes Figure 16 Sectional view of XVII-XVII'.

[0035] Figure 18 This is a coordinate graph showing the filter characteristics of the elastic wave filter involved in Embodiment 1-1.

[0036] Figure 19 This is a coordinate graph showing the relationship between the impedance and frequency of the series arm resonator of the elastic wave filter involved in Embodiment 1-1.

[0037] Figure 20This is a coordinate graph showing the relationship between the impedance and frequency of the parallel arm resonator of the elastic wave filter involved in Embodiment 1-1.

[0038] Figure 21 This is a coordinate graph showing the relationship between the real part of the impedance of the series arm resonator of the elastic wave filter involved in Embodiment 1-1 and the frequency.

[0039] Figure 22 This is a coordinate graph showing the relationship between the real part of the impedance of the parallel arm resonator of the elastic wave filter involved in Embodiment 1-1 and the frequency.

[0040] Figure 23 This is a coordinate graph showing the filter characteristics of the elastic wave filters involved in Examples 1-1, 1-2 and Comparative Example 1.

[0041] Figure 24 It is Figure 23 The coordinate graph showing the vicinity of the frequency band indicated by arrow A1 is magnified.

[0042] Figure 25 This is a coordinate graph showing the vicinity of the passband of the elastic wave filter involved in Examples 1-3 and Comparative Example 1.

[0043] Figure 26 This is a coordinate graph showing the vicinity of the passband of the elastic wave filter involved in Examples 1-4 and Comparative Example 1.

[0044] Figure 27 This is a top view showing the structure of the elastic wave resonator involved in Embodiment 2.

[0045] Figure 28 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-2.

[0046] Figure 29 This is a coordinate graph showing the relationship between the real part of the impedance and the frequency of the elastic wave resonator involved in Embodiments 2-1 and 2-2.

[0047] Figure 30 This is a coordinate graph showing the relationship between the impedance and frequency of the elastic wave resonator involved in Embodiment 3.

[0048] Figure 31 This is a coordinate graph showing the relationship between the real part of the impedance and the frequency of the elastic wave resonator involved in Embodiment 3.

[0049] Figure 32 This is a coordinate graph showing the relationship between the real part of the impedance of the elastic wave resonator involved in Embodiment 3 and the width of the frame electrode.

[0050] Figure 33 This is a coordinate graph showing the relationship between the Q value of the elastic wave resonator involved in Embodiment 3 and the width of the frame electrode.

[0051] Figure 34 This is a coordinate graph showing the relationship between the real part of the impedance of the elastic wave resonator involved in Embodiment 4 and the length of the frame electrode.

[0052] Figure 35 This is a coordinate graph showing the relationship between the Q value of the elastic wave resonator involved in Embodiment 4 and the length of the frame electrode.

[0053] Figure 36 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonator involved in Embodiment 5 and Embodiments 4-5.

[0054] Figure 37 This is a coordinate graph showing the relationship between the real part of the impedance and the frequency of the elastic wave resonator involved in Embodiment 5 and Embodiments 4-5.

[0055] Figure 38 This is a coordinate graph showing the relationship between the Euler angles and fractional bandwidth of the piezoelectric element using lithium niobate in the elastic wave resonator involved in Embodiment 6-1.

[0056] Figure 39 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 involved in Embodiment 6-2.

[0057] Figure 40 This is a diagram illustrating the structure of the communication device according to the second embodiment. Detailed Implementation

[0058] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. It should be noted that the present disclosure is not limited by these embodiments. It should also be noted that the embodiments described in this disclosure are illustrative, and partial substitutions or combinations of structures are possible 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 produced by the same structure will not be mentioned repeatedly in each embodiment.

[0059] (First Implementation)

[0060] 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, and inductors 68A and 68B. At least one of the plurality of series arm resonators 61, 62, 63, 64 and the plurality of parallel arm resonators 65, 66, 67 is a resonator utilizing a bulk wave with a thickness longitudinal vibration mode, i.e., a BAW (Bulk Acoustic Wave) element. However, it is not limited to this; at least one of the plurality of series arm resonators 61, 62, 63, 64 and the plurality of parallel arm resonators 65, 66, 67 may also be a resonator utilizing a bulk wave with a shear vibration mode.

[0061] 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, and 67 are connected in parallel between the signal path between input terminal 60A and output terminal 60B and grounds 69A, 69B, and 69C. The elastic wave filter 50 according to the first embodiment is called a trapezoidal filter.

[0062] One terminal of each of the series-connected series arm resonators 61, 62, 63, and 64 is electrically connected to input terminal 60A, and the other terminal is electrically connected to 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 68A. 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 via inductor 68B. One terminal of the parallel arm resonator 67 is electrically connected to the signal path connecting series arm resonators 63 and 64, and the other terminal is electrically connected to ground 69C.

[0063] Inductor 68A is connected in series in the signal path between the parallel arm resonator 65 and ground 69A. Inductor 68B is connected in series in the signal path between the parallel arm resonator 66 and ground 69B.

[0064] As impedance elements, the inductors 68A and 68B are not limited to those; the elastic wave filter 50 may also include capacitors, etc. Furthermore, the impedance elements such as inductors 68A and 68B and capacitors are not limited to a structure connected to parallel arm resonators 65, 66, and 67; 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 68A and 68B and capacitors. In this case, the frequency of the filter characteristics of the elastic wave filter 50 can be varied by switching the switching elements on and off.

[0065] The series arm resonators 61, 62, 63, and 64 are configured as two resonators s1, s2, s3, and s4, each with a series division. The number of divisions for each of the series arm resonators 61, 62, 63, and 64 is even. The number of divisions for each of the series arm resonators 61, 62, 63, and 64 is not limited to two; they may also be undivided or have three or more divisions.

[0066] Furthermore, the parallel arm resonators 65, 66, and 67 are configured such that each has two resonators p1, p2, and p3 connected in series. The number of segments in each of the multiple parallel arm resonators 65, 66, and 67 is even. The number of segments in each of the multiple parallel arm resonators 65, 66, and 67 is not limited to two; they may also be unconnected or have three or more segments. It should be noted that in the following description, "connected in series" refers to a structure in which multiple resonators with the same resonant frequency are connected in series.

[0067] Detailed structures of the series arm resonators 61, 62, 63, and 64, and the parallel arm resonators 65, 66, and 67, will follow later. Figure 7 This will be discussed later. Furthermore, the series arm resonators 61, 62, 63, and 64, and the parallel arm resonators 65, 66, and 67, respectively, have the effect of having multiple resonators s1, s2, s3, s4, p1, p2, and p3 separated in series, which will also be discussed later. Figure 7 To be continued.

[0068] 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 can be appropriately changed according to the required filter characteristics. For example, the elastic wave filter 50 may also have a structure including at least one series arm resonator and at least one parallel arm resonator.

[0069] Figure 2 This is a schematic cross-sectional view illustrating the structure of the elastic wave filter according to the first embodiment. Figure 3 This is a top view schematically illustrating 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 showing the back of the module substrate in the elastic wave filter according to the first embodiment.

[0070] like Figure 2As 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 is configured to include... Figure 1 The multiple series arm resonators 61, 62, 63, 64 and the multiple parallel arm resonators 65, 66, 67 are shown.

[0071] The module substrate 52 is a laminated substrate having multiple dielectric layers 53 and 54. For example, a printed circuit board including resin, or a ceramic substrate such as LTCC (Low Temperature Co-fired Ceramics) or HTCC (High Temperature Co-fired Ceramics) can be used for the module substrate 52. The module substrate 52 is not limited to two dielectric layers 53 and 54; it may also have three or more dielectric layers, or it may be a single-layer substrate.

[0072] like Figure 3 As shown, the resonator chip 51 has multiple series-arm resonators 61, 62, 63, 64, multiple parallel-arm resonators 65, 66, 67, and multiple terminals (input terminal 60A, output terminal 60B, and ground terminals 69A, 69B, 69C, 69D) arranged on the support member 13. 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, and the multiple terminals (input terminal 60A, output terminal 60B, and ground terminals 69A, 69B, 69C, 69D) is as follows: Figure 1 Same, repeated descriptions omitted.

[0073] like Figure 4 As 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 back side of the module substrate 52 vias 58A.

[0074] like Figure 5 As shown, inductors 68A and 68B are formed on the inner layer of the module substrate 52. One end of inductors 68A and 68B 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.

[0075] like Figure 6 As shown, multiple connection pads 59 are provided on the back of the module substrate 52. The elastic wave filter 50 is mounted on the high-frequency front-end circuit 101 (see reference 101) via the multiple connection pads 59. Figure 40 External devices such as )

[0076] Next, the detailed structure of the series arm resonator 61 will be described. Figure 7 This is a top view schematically illustrating 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 and Figure 8 The structure of the series arm resonator 61 among the multiple resonators in the resonator chip 51 is shown in an enlarged manner. That is, Figure 7 and Figure 8 The structure of the series arm resonator 61 located on the input terminal 60A side is shown among a plurality of resonators.

[0077] It should be noted that in the following description, unless there is a need to distinguish between multiple series-arm resonators 61, 62, 63, 64 and multiple parallel-arm resonators 65, 66, 67 (multiple resonators s1, s2, s3, s4, p1, p2, p3), they will only be referred to as elastic wave resonator 10. Furthermore, the cross-sectional structures of the other resonators are similar to... Figure 8 The cross-sectional structure of the series arm resonator 61 shown is the same, regarding Figure 8 The description of the cross-sectional structure of the series arm resonator 61 can also be applied to other resonators.

[0078] First, the structure of one of the resonators s1 (elastic wave resonator 10) included in the series arm resonator 61 will be described. For example... Figure 7 and 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, a lower electrode 32, a piezoelectric body 20, an upper electrode 31, lead wires 34 and 35, and a frame electrode 33 are stacked sequentially on the support member 13.

[0079] 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).

[0080] 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 includes silicon (Si), quartz, etc. 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. It should be noted that the support member 13 may also have a structure without the intermediate layer 12 and with the piezoelectric body 20 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).

[0081] 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, during excitation, the energy loss of the bulk wave is reduced, and good resonance characteristics are obtained.

[0082] 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 comprising a single crystal of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). The piezoelectric material 20 is not limited to these materials and may also use aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), etc. The thickness of the piezoelectric material 20 is not particularly limited, but is preferably 1 μm or less. Alternatively, the piezoelectric material 20 may be a structure obtained by stacking multiple layers of piezoelectric materials with different crystal orientations.

[0083] 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 and Figure 8 As 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 bulk 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.

[0084] It should be noted that the names such as upper electrode 31 and lower electrode 32 are used only for defining 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 circular or other shapes.

[0085] 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. Additionally, a bonding layer such as Ti or NiCr may be present between the upper electrode 31 and the support member 13 (intermediate layer 12).

[0086] 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 in the two resonators s1 that constitute the series arm resonator 61. In other words, a recess 14 is provided for two resonators s1.

[0087] 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 separately arranged 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 piezoelectric element 20 is positioned opposite the upper electrode 31 of a resonator s1. Additionally, another region in the X direction of the lower electrode 32 ( Figure 8 The left part of the piezoelectric element 20 is positioned opposite the upper electrode 31 of another resonator s1.

[0088] Lead wires 34 and 35 are disposed on the same layer as the upper electrode 31 and are connected in the X direction of the upper electrode 31. 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 positioned opposite each other in the X direction.

[0089] 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.

[0090] Additionally, a through-hole 15 is provided in the region of the piezoelectric body 20 that overlaps with the recess 14. The through-hole 15 is provided for etching the sacrificial layer during the formation of the recess 14. The location and number of through-holes 15 are not limited to... Figure 7 The example shown can be modified as appropriate. Additionally, in the following embodiments and examples, the through hole 15 is sometimes omitted.

[0091] 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 diaphragm structure. However, it is not limited to this, the elastic wave resonator 10 may also be a solidly mounted resonator (SMR) in which multiple low-impedance layers and high-impedance layers are stacked instead of the recess 14 (cavity).

[0092] It should be noted that, in Figure 1 and Figure 3 In the example shown, all the series arm resonators 61, 62, 63, and 64, and all the parallel arm resonators 65, 66, and 67 are connected in series. However, this is not a limitation; at least one of the series arm resonators 64 closest to the output terminal 60B may be configured to be connected in series. Alternatively, at least one of the parallel arm resonators 65, 66, and 67 closest to the output terminal 60B may be configured to be connected in series.

[0093] In this embodiment, since multiple series-arm resonators 61, 62, 63, 64 and multiple parallel-arm resonators 65, 66, 67 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 multiple parallel-arm resonators 65, 66, 67 decreases, improving power handling performance. More specifically, the area S of the upper electrode 31 represents the area of ​​the excitation region where the upper electrode 31 and the lower electrode 32 overlap.

[0094] Multiple series-arm resonators 61, 62, 63, 64 and multiple parallel-arm resonators 65, 66, 67 are not limited to a series-series split structure; they can also be split in parallel. In this case, especially when the impedance of the resonant circuit is low, the parallel split can suppress the enlargement of the recess 14 region and suppress the decrease in the mechanical strength of each resonator.

[0095] Here, in the elastic wave filter 50 using BAW resonators, the spectrum of the second harmonic may sometimes be output due to the nonlinear operation of the BAW resonators. Furthermore, in the elastic wave filter 50, the second harmonic spectrum of each resonator is attenuated by the resonator on the output side before being output from the output terminal 60B. However, the second harmonic spectrum of a resonator close to the output terminal 60B (e.g., the series arm resonator 64) may be output from the output terminal 60B with almost no attenuation.

[0096] In this embodiment, the series arm resonator 64, located at least near the output terminal 60B, has two resonators s4 separated in series. Alternatively, the parallel arm resonator 67, located at least near the output terminal 60B, has two resonators p3 separated in series. Thus, in this embodiment, the second harmonic spectrum output from the output terminal 60B can be suppressed.

[0097] For example, when the resonator is divided into n segments in series (n is an integer), the energy density becomes n compared to the undivided resonator. 2 One-third. Therefore, for example, in Figure 7 , 8 In the series arm resonator 61 shown, the nonlinear effect is reduced by 6 dB compared to the unsplit structure.

[0098] In addition, such as Figure 7 , 8 As 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 a via to connect the lower electrode 32 to the first main surface 20a side of the piezoelectric body 20, which can suppress manufacturing costs.

[0099] In addition, Figure 7 , 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 in the series arm resonator 61 is even; therefore, one resonator s1 (e.g., Figure 7 , Figure 8 The relationship between the voltage and polarization axis on the right side (refer to arrows G1, G3) and another resonator s1 (e.g. Figure 7 , Figure 8 The voltage on the left side (refer to arrows G2 and G4) shows an inverse relationship with the polarization axis. Therefore, the second-order nonlinear signal is canceled out, which can reduce the second-harmonic spectrum.

[0100] 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). As a result, the nonlinear signals of the series-connected resonators s1 become the same magnitude, thus canceling out the second nonlinear signals.

[0101] Next, refer to Figures 8 to 10 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 10 It is Figure 9 A top view showing an enlarged portion of the upper electrode and frame electrode. Figure 9 and Figure 10 The structure of an elastic wave resonator 10 will be described in the following section.

[0102] like Figure 8 As shown, the frame electrode 33 is grounded to the upper electrode 31 and is disposed on the upper surface of the upper electrode 31 (the side opposite to the piezoelectric body 20). For example... 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, having a short side extending along the X direction and a long side extending along the Y direction.

[0103] In this embodiment, the shape of the upper electrode 31 is defined by the frame electrode 33. Specifically, the length Wx1 of the upper electrode 31 in the X direction is equal to the maximum length of the frame electrode 33 in the X direction. More specifically, the length Wx1 of the upper electrode 31 in the X direction is equal to the maximum length in the X direction between the outer edges of two adjacent long sides of the frame electrode 33. Furthermore, the length Wy1 of the upper electrode 31 in the Y direction is equal to the maximum length in the Y direction of the frame electrode 33. More specifically, the length Wy1 of the upper electrode 31 in the Y direction is equal to the maximum length in the Y direction between the outer edges of two adjacent short sides of the frame electrode 33.

[0104] like Figure 9 and Figure 10As shown, the frame electrode 33 includes a plurality of first portions 33a and a plurality of second portions 33b having a width larger than that of the first portions 33a. The plurality of first portions 33a and the plurality of second portions 33b are alternately arranged along the outer periphery of the upper electrode 31. The plurality of second portions 33b protrude towards the inner periphery of the frame electrode 33 beyond the plurality of first portions 33a. Therefore, the frame electrode 33 has a concave-convex shape along its inner periphery in the planar direction. Furthermore, the outer periphery of the frame electrode 33 does not have a concave-convex shape in the planar direction and is formed as a straight line. Additionally, the second portions 33b of the frame electrode 33 are not located at the corner where the long side and short side of the frame electrode 33 connect. In other words, the corner of the frame electrode 33 is formed by connecting the first portion 33a of the long side to the first portion 33a of the short side.

[0105] More specifically, such as Figure 10 As shown, on the long side of the frame electrode 33, the first portion 33a has a first width FWx1 in the X direction perpendicular to the extending direction of the frame electrode 33. The second portion 33b has a second width FWx2 in the X direction that is larger than the first width FWx1. Furthermore, on the short side of the frame electrode 33, the first portion 33a has a first width FWy1 in the Y direction perpendicular to the extending direction of the frame electrode 33. The second portion 33b has a second width FWy2 in the Y direction that is larger than the first width FWy1. The first widths FWx1 and FWy1 are the lengths between the outer and inner edges of the first portion 33a in the direction perpendicular to the extending direction of the frame electrode 33, respectively. Similarly, the second widths FWx2 and FWy2 are the lengths between the outer and inner edges of the second portion 33b in the direction perpendicular to the extending direction of the frame electrode 33, respectively.

[0106] In this embodiment, the first width FWx1 of the first portion 33a on the long side of the frame electrode 33 is equal to the first width FWy1 of the first portion 33a on the short side of the frame electrode 33. Furthermore, the second width FWx2 of the second portion 33b on the long side of the frame electrode 33 is equal to the second width FWy2 of the second portion 33b on the short side of the frame electrode 33.

[0107] In the following description, unless there is a need to distinguish between the first width FWx1 and the first width FWy1 in the first part 33a, it will only be referred to as the first width FW1. Similarly, unless there is a need to distinguish between the second width FWx2 and the second width FWy2 in the second part 33b, it will only be referred to as the second width FW2.

[0108] Furthermore, in a direction parallel to the extending direction of the frame electrode 33, the first portion 33a has a first length FL1, and the second portion 33b has a second length FL2. The first length FL1 of the first portion 33a on the long side of the frame electrode 33 is equal to the first length FL1 of the first portion 33a on the short side of the frame electrode 33. Similarly, the second length FL2 of the second portion 33b on the long side of the frame electrode 33 is equal to the second length FL2 of the second portion 33b on the short side of the frame electrode 33.

[0109] In the elastic wave resonator 10, depending on the mode of the standing wave residing in the frame electrode 33 (Border Ring Mode (BRM)), the loss at a specified frequency sometimes increases. In this embodiment, the frame electrode 33 includes a plurality of first portions 33a having a first width FW1 and a plurality of second portions 33b having a second width FW2. The first portions 33a and the second widths FW2 of the frame electrode 33 are arranged alternately and have an uneven shape along the inner periphery of the frame electrode 33 in the planar direction. Therefore, the standing wave modes affected by the first portions 33a and the standing wave modes affected by the second portions 33b are dispersed along the frequency axis, suppressing the loss at the specified frequency.

[0110] In the following description, the frame electrode 33 having a plurality of first portions 33a and a plurality of second portions 33b is referred to as "a frame electrode 33 having a concave-convex shape in the planar direction". In addition, the frame electrode 33 not having a plurality of first portions 33a and a plurality of second portions 33b is referred to as "a frame electrode 33 not having a concave-convex shape and having a fixed width".

[0111] like Figure 3 As shown, in the elastic wave filter 50 of this embodiment, the frame electrodes 33 of the series arm resonators 61, 62, 63, and 64 are rectangular, having multiple first portions 33a and multiple second portions 33b, and have a concave-convex shape in the planar direction. The frame electrodes 33 of the parallel arm resonators 65, 66, and 67 are circular, do not have multiple first portions 33a and multiple second portions 33b, and have a fixed width.

[0112] Detailed structural examples and filter characteristics of the frame electrodes 33 of series arm resonators 61, 62, 63, and 64 and the frame electrodes 33 of parallel arm resonators 65, 66, and 67 will be described later in Examples 1 to 5.

[0113] It should be noted that in this embodiment, the structure in which the frame electrode 33 is disposed on the upper electrode 31 has been described, but it is not limited thereto. The frame electrode 33 may also be disposed on the lower electrode 32, or it may be disposed on both the upper electrode 31 and the lower electrode 32. In this case, regarding Figure 9and Figure 10 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 described as the shape of the region (excitation region) where the upper electrode 31 and the lower electrode 32 overlap. In addition, the frame electrode 33 is not limited to having a concave-convex shape along the inner periphery of the frame electrode 33 in the planar direction, but can also have a concave-convex shape along the outer periphery of the frame electrode 33.

[0114] Furthermore, the "arrangement along the outer periphery" of the frame electrode 33 includes a structure in which the frame electrode 33 is grounded to the outer periphery end of the upper electrode 31 or the lower electrode 32, and a structure in which the frame electrode 33 is arranged slightly inwardly to the outer periphery end of the upper electrode 31 or the lower electrode 32 at a predetermined interval. More specifically, for example, when the area of ​​the lower electrode 32 is smaller than that of the upper electrode 31 (see...). Figure 14 If the area of ​​the lower electrode 32 is smaller than that of the upper electrode 31 and the frame electrode 33 is disposed above the upper electrode 31, then the frame electrode 33 needs to be disposed along the portion of the upper electrode 31 that overlaps with the outer periphery of the lower electrode 32.

[0115] exist Figure 9 To make the explanation easier to understand, the case where the frame electrode 33 is rectangular, that is, the case where the upper electrode 31 has a rectangular shape, 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.

[0116] Figure 11 This is a top view showing the structure of the upper electrode and frame electrode involved in the first modified example. (See attached image.) Figure 11 As shown, the upper electrode 31 and the frame electrode 33A involved in the first modified example are elliptical in shape. More specifically, the upper electrode 31 and the frame electrode 33A are elliptical in shape with a major axis along the Y direction. That is, the length Wx1 of the upper electrode 31 is defined by the maximum length in the X direction of the elliptical shape. In addition, the length Wy1 of the upper electrode 31 is defined by the maximum length in the Y direction of the elliptical shape.

[0117] Furthermore, in this modified example, the frame electrode 33A also has a plurality of first portions 33Aa and a plurality of second portions 33Ab. The plurality of first portions 33Aa and the plurality of second portions 33Ab are alternately arranged along the outer periphery of the upper electrode 31. Thus, the frame electrode 33A has a concave-convex shape along the inner periphery of the frame electrode 33A in the planar direction. The definitions of the first width FW1 of the first portion 33Aa and the second width FW2 of the plurality of second portions 33Ab of the frame electrode 33A in the second modified example are the same as those in the first embodiment described above.

[0118] Figure 12 This is a top view showing the structure of the upper electrode and frame electrode involved in the second modified example. (See attached image.) Figure 12 As shown, in the second modification, the upper electrode 31 and the frame electrode 33B are rectangular in shape, formed by rounded corners. In other words, the portion of the frame electrode 33B along its long side and the portion along its short side are smoothly connected in a rounded shape. Alternatively, the upper electrode 31 and the frame electrode 33B may also be oblong in shape. The definitions of the lengths Wx1 and Wy1 of the upper electrode 31, the first width FW1 of the first portion 33Ba of the frame electrode 33B, and the second width FW2 of the plurality of second portions 33Bb in the second modification are the same as in the first embodiment described above. In addition, the second portions 33Bb of the frame electrode 33B are not provided at the rounded corners of the frame electrode 33. In other words, the corners of the frame electrode 33 are formed by rounded bending of the first portion 33Ba.

[0119] Figure 13 This is a top view showing the structure of the upper electrode and frame electrode involved in the third modified example. For example... Figure 13 As shown, in the third modification, the upper electrode 31 and the frame electrode 33C are polygonal. The first side 33Cs1, the second side 33Cs2, and the third side 33Cs3 of the frame electrode 33C extend in directions inclined at angles relative to the X and Y directions, respectively. In this modification, the length Wx1 of the upper electrode 31 is also the maximum length of the frame electrode 33C in the X direction. Furthermore, the length Wy1 of the upper electrode 31 is the maximum length of the frame electrode 33C in the Y direction.

[0120] In the third variation, the first side 33Cs1, the second side 33Cs2, and the third side 33Cs3 each have multiple first portions 33Ca and multiple second portions 33Cb. Thus, the frame electrode 33C has a concave-convex shape along its inner periphery in the planar direction. Furthermore, in this variation, the second portions 33Cb of the frame electrode 33C are not located at the corners (the connection points of the first sides 33Cs1, the second side 33Cs2, and the third side 33Cs3).

[0121] Figure 14This is a cross-sectional view showing the structure of the upper electrode and frame electrode involved in the fourth modified example. For example... Figure 14 As shown, in the fourth modification, the periphery of the upper electrode 31 is disposed separately from the piezoelectric body 20 through the insulating layer 22. In this case, the length Wy1 of the upper electrode 31 is defined by the portion of the upper electrode 31 that is connected to the piezoelectric body 20 and has a frame electrode 33 (the portion stacked in the order of piezoelectric body 20, upper electrode 31, and frame electrode 33). The portion of the upper electrode 31 that is disposed separately from the piezoelectric body 20 (the portion stacked in the order of piezoelectric body 20, insulating layer 22, upper electrode 31, and frame electrode 33) is not included in the length Wy1. That is, the length Wy1 of the upper electrode 31 in the Y direction is the length of the portion of the upper electrode 31 that is connected to the piezoelectric body 20 and has a frame electrode 33.

[0122] Furthermore, the first width FW1 of the first portion 33a of the frame electrode 33 is defined by the portion of the frame electrode 33 that overlaps with the area where it is in contact with the upper electrode 31 and the piezoelectric body 20 (the portion stacked in the order of piezoelectric body 20, upper electrode 31, and frame electrode 33). The portion of the frame electrode 33 that overlaps with the area where it is separated from the upper electrode 31 and the piezoelectric body 20 (the portion stacked in the order of piezoelectric body 20, insulating layer 22, upper electrode 31, and frame electrode 33) is not included in the first width FW1. That is, the first width FW1 of the first portion 33a of the frame electrode 33 is the length in the Y direction (the direction perpendicular to the extension direction of the frame electrode 33) of the portion of the frame electrode 33 that overlaps with the area where it is in contact with the upper electrode 31 and the piezoelectric body 20.

[0123] It should be noted that, in Figure 14 The length Wy1 of the upper electrode 31 in the Y direction and the first width FW1 of the frame electrode 33 in the Y direction are described, but... Figure 14 The explanation can also be applied to the X direction. Additionally, in Figure 14 In the text, the first width FW1 of the first portion 33a of the frame electrode 33 is described, but the same applies to the second width FW2 of the second portion 33b.

[0124] Figure 15 This is a top view showing the structure of the series arm resonator involved in the fifth variation. Figure 7 , 8 The example shown illustrates a structure in which two resonators s1, split in series in a series arm resonator 61, form a recess 14, but is not limited to this. Figure 15 As shown, in the series arm resonator 61A involved in the fifth modification, recesses 14a and 14b are respectively provided in the two series-split resonators s1.

[0125] The two recesses 14a and 14b are arranged separately in the X direction. One resonator s1 of the series arm resonator 61A (e.g., Figure 15 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 15 The upper electrode 31 (on the left side) is arranged overlapping another recess 14b. The lower electrode 32 is continuously arranged across the two recesses 14a and 14b.

[0126] 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.

[0127] Figure 16 This is a top view showing the structure of the upper electrode and frame electrode involved in the sixth modified example. Figure 17 yes Figure 16 The XVII-XVII' cross-sectional view. In the first embodiment and various modifications described above, the structure in which the frame electrode 33 has a concave-convex shape along the inner periphery of the frame electrode 33 in the planar direction has been described, but it is not limited thereto.

[0128] like Figure 16 and Figure 17 As shown, the frame electrode 33D involved in the sixth modification has a plurality of first portions 33Da and a plurality of second portions 33Db that are higher than the first portions 33Da. In addition, the plurality of first portions 33Da and the plurality of second portions 33Db have equal widths in top view and are arranged alternately along the extension direction of the frame electrode 33D.

[0129] like Figure 17 As shown, the second height FH2 of the plurality of second portions 33Db is higher than the first height FH1 of the plurality of first portions 33Da. According to this structure, the frame electrode 33D has a concave-convex shape in the Z direction. It should be noted that the first height FH1, in the Z direction (the direction perpendicular to the first main surface 20a of the piezoelectric body 20), is the length between the lower surface (the surface in contact with the upper electrode 31) and the upper surface (the surface opposite to the upper electrode 31) of the first portion 33Da. Similarly, the second height FH2, in the Z direction (the direction perpendicular to the first main surface 20a of the piezoelectric body 20), is the length between the lower surface (the surface in contact with the upper electrode 31) and the upper surface (the surface opposite to the upper electrode 31) of the second portion 33Db.

[0130] In the sixth variation, the mass per unit area of ​​the plurality of first portions 33Da and the plurality of second portions 33Db of the frame electrode 33D is different. Therefore, similar to the first embodiment described above, the standing wave mode affected by the first portion 33Da and the standing wave mode affected by the second portion 33Db are dispersed along the frequency axis, suppressing the loss at the specified frequency.

[0131] Next, the filter characteristics will be explained when the structure of the frame electrode 33 of the series arm resonators 61, 62, 63, and 64 differs from the structure of the frame electrode 33 of the parallel arm resonators 65, 66, and 67. Furthermore, regarding the elastic wave resonator 10 constituting the series arm resonators 61, 62, 63, and 64 and the parallel arm resonators 65, 66, and 67, the resonator characteristics will be explained when the shapes of the first width FW1, second width FW2, etc., of the frame electrode 33 differ.

[0132] In the following embodiments and comparative examples, a single crystal of lithium niobate was used as the material for the piezoelectric body 20. The Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric body 20 are (φ, θ, ψ) = (0°, 126°, 0°).

[0133] The upper electrode 31 is stacked from the first main surface 20a of the piezoelectric body 20 in the order of Ti / Pt / Ti / Al / Ti. The film thicknesses of Ti / Pt / Ti / Al / Ti are 4 / 20.6 or more and 58.2 or less / 14 / 100 / 4 nm, respectively. The lower electrode 32 is stacked from the second main surface 20b of the piezoelectric body 20 in the order of Ti / Pt / Ti / Al / Ti. The film thicknesses of Ti / Pt / Ti / Al / Ti are 4 / 20.59 or more and 58.21 or less / 14 / 100 / 4 nm, respectively.

[0134] The frame electrode 33 is stacked on the surface of the upper electrode 31 in the order of Ti / Pt / Ti. The film thicknesses of Ti / Pt / Ti are 4 / 30 / 4 nm, respectively.

[0135] 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).

[0136] Additionally, Tables 1 to 4 of the various embodiments described below and Figures 18 to 39 This includes deviations in filter characteristics and resonator characteristics caused by processing deviations in the manufacturing process.

[0137] (Example 1)

[0138] In Examples 1-1, 1-2 and Comparative Example 1, the filter characteristics are described when the frame electrodes 33 of at least the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67 have a concave-convex shape in the planar direction.

[0139] First, the filter characteristics of the elastic wave filter 50 involved in Embodiment 1-1 and the resonator characteristics of each elastic wave resonator 10 constituting the elastic wave filter 50 will be explained. Figure 18 This is a coordinate graph showing the filter characteristics of the elastic wave filter involved in Embodiment 1-1. Figure 19 This is a coordinate graph showing the relationship between the impedance and frequency of the series arm resonator of the elastic wave filter involved in Embodiment 1-1. Figure 20 This is a coordinate graph showing the relationship between the impedance and frequency of the parallel arm resonator of the elastic wave filter involved in Embodiment 1-1. Figure 21 This is a coordinate graph showing the relationship between the real part of the impedance of the series arm resonator of the elastic wave filter involved in Embodiment 1-1 and the frequency. Figure 22 This is a coordinate graph showing the relationship between the real part of the impedance and frequency of the parallel arm resonators of the elastic wave filter according to Embodiment 1-1. Table 1 shows structural examples of each resonator of the elastic wave filter according to Embodiment 1.

[0140] In Embodiment 1-1, the frame electrodes 33 of the series arm resonators 61, 62, 63, and 64 are rectangular with a concave-convex shape in the planar direction, while the frame electrodes 33 of the parallel arm resonators 65, 66, and 67 are circular without a concave-convex shape (see reference). Figure 2 ).

[0141] [Table 1]

[0142]

[0143] As shown in Table 1, in the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4), the first width FW1 (FWx1, FWy1) of the first portion 33a of the frame electrode 33 is 1.2 μm, and the second width FW2 (FWx2, FWy2) of the second portion 33b is 1.4 μm. That is, in the frame electrode 33 of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4), the second width FW2 of the second portion 33b is larger than the first width FW1 of the first portion 33a.

[0144] The width ratio RW shown in Table 1 is the ratio of the difference between the first width FW1 and the second width FW2 to the first width FW1, and is expressed by the following formula (1).

[0145] RW=((FW2-FW1) / FW1)×100%… (1)

[0146] In the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4), the width ratio RW of the frame electrode 33 is 16.67%.

[0147] The length ratio RL shown in Table 1 is the ratio of the length of the frame electrode 33 along its outer periphery (i.e., the length of the entire circumference of the frame electrode 33) to the sum of the second lengths FL2 of the plurality of second parts 33b along their outer periphery. When the frame electrode 33 is rectangular, the length of the outer periphery of the frame electrode 33 is (Wx1 + Wy1) ​​× 2. In addition, when the total number of second parts 33b is set to n, the sum of the second lengths FL2 is FL2 × n. In Embodiment 1, the length ratio RL is expressed by the following formula (2). It should be noted that the example in formula (2) where the length (Wx1 + Wy1) ​​× 2 of the frame electrode 33 along its outer periphery is rectangular is used with different values ​​depending on the shape of the frame electrode 33.

[0148] RL=(FL2×n) / ((Wx1+Wy1)×2)×100%… (2)

[0149] In the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4), the length ratio RL of the frame electrode 33 is 58.0.

[0150] In contrast, in the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3), the first width FW1 (FWx1, FWy1) and the second width FW2 (FWx2, FWy2) of the frame electrode 33 are both 1.2 μm. That is, in the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3), the second width FW2 of the frame electrode 33 is equal to the first width FW1, and the frame electrode 33 does not have a concave or convex shape. Furthermore, in the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3), the width ratio RW and the length ratio RL of the frame electrode 33 are both 0.

[0151] Furthermore, the lengths Wx1, Wy1, 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 all different. Similarly, the lengths Wx1, Wy1, and area S of the upper electrode 31 of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) are all different.

[0152] The materials of the upper electrode 31, lower electrode 32, and frame electrode 33 are shared in the series arm resonators 61, 62, 63, 64 (resonators s1, s2, s3, s4) and the parallel arm resonators 65, 66, 67 (resonators p1, p2, p3). 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 (resonators p1, p2, p3). Furthermore, the film thickness of Pt in the series arm resonators 61, 64 (resonators s1, s4) on the input terminal 60A side and the output terminal 60B side is thinner than that in the series arm resonators 62, 63 (resonators s2, s3). The film thickness of Pt in the parallel arm resonators 65 and 67 (resonators p1 and p3) on the input terminal 60A side and the output terminal 60B side is greater than the film thickness of Pt in the parallel arm resonator 66 (resonator p2).

[0153] like Figure 18 As shown, the elastic wave filter 50 involved in Embodiment 1-1 has a loss of less than 2.0 dB in the frequency band indicated by arrow A1 (n77 frequency band: above 3300MHz and below 4200MHz).

[0154] Furthermore, the elastic wave filter 50 according to Embodiment 1-1 achieves attenuation of 15 dB or more in the frequency band indicated by arrow A2 (LTE band: 2690 MHz and below). Additionally, the elastic wave filter 50 according to Embodiment 1-1 achieves attenuation of 38 dB or more in the frequency band indicated by arrow A3 (n79 band: 4400 MHz and above and 5000 MHz and below). Furthermore, the elastic wave filter 50 according to Embodiment 1-1 achieves attenuation of 22 dB or more in the frequency band indicated by arrow A4 (WiFi7 band: 5150 MHz and above and 7125 MHz and below).

[0155] As shown above, the elastic wave filter 50 involved in Embodiment 1-1 has good filter characteristics.

[0156] like Figure 19 As shown, the impedances of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) in the elastic wave filter 50 vary depending on the area S of the upper electrode 31. Furthermore, the resonant frequencies fr of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) are greater than the passband of the elastic wave filter 50 (see reference). Figure 18 The low-frequency end of arrow A1) has a high frequency. The resonant frequency fr of the series arm resonators 61, 62, 63, 64 (resonators s1, s2, s3, s4) is configured within the passband, and the anti-resonant frequency fa is configured in the attenuation band, which is higher than the passband.

[0157] like Figure 20 As shown, the resonant frequency fr of the parallel arm resonators 65, 66, 67 (resonators p1, p2, p3) of the elastic wave filter 50 is greater than the passband of the elastic wave filter 50 (refer to...). Figure 18 The low-frequency end of arrow A1) has a low frequency. That is, the anti-resonance frequency fa of the parallel arm resonators 65, 66, 67 (resonators p1, p2, p3) is configured in the passband, and the resonant frequency fr is configured in the attenuation band which is lower than the passband.

[0158] like Figure 21 As shown, the occurrence frequency of the boundary ring mode of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is approximately 3500 MHz. Additionally, as... Figure 22 As shown, the occurrence frequency of the boundary ring modes of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) is approximately 2600 MHz. When comparing the real part of the impedance at the occurrence frequency of the boundary ring modes of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) and the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3), the real part of the impedance of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4), including the frame electrode 33 with its concave-convex shape, is smaller.

[0159] In embodiment 1-1, the elastic wave filter 50 has a plurality of elastic wave resonators 10, and the series arm resonators 61, 62, 63, 64 (resonators s1, s2, s3, s4) with a resonant frequency fr higher than the low-frequency end of the passband are provided with frame electrodes 33 including a plurality of first portions 33a and a plurality of second portions 33b and having a concave-convex shape in the planar direction. According to Figure 21 and Figure 22 The results shown in Example 1-1 demonstrate that the mode of the standing wave residing in the frame electrode 33 within the passband is dispersed along the frequency axis, suppressing losses within the passband.

[0160] In addition, such as Figure 21 and Figure 22As shown, the real part of the impedance at the anti-resonant frequency fa of the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) is larger than that of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3). That is, compared with the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) which do not have a concave-convex frame electrode 33, the series arm resonators 61, 62, 63, and 64 (resonators s1, s2, s3, and s4) have greater energy leakage to the outside of the frame electrode 33 (outside the excitation region), and the Q value at the anti-resonant frequency fa decreases.

[0161] In other words, in Embodiment 1-1, the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) of the plurality of elastic wave resonators 10 in the elastic wave filter 50, whose anti-resonance frequency fa is configured within the passband, have frame electrodes 33 without concave or convex shapes. As a result, the Q of the parallel arm resonators 65, 66, and 67 (resonators p1, p2, and p3) at the anti-resonance frequency fa is improved. Consequently, the elastic wave filter 50 is able to suppress losses in the passband.

[0162] Figure 23 This is a coordinate graph showing the filter characteristics of the elastic wave filters involved in Examples 1-1, 1-2 and Comparative Example 1. Figure 24 It is Figure 23 The coordinate graph is magnified and shows the vicinity of the frequency band indicated by arrow A1. Figure 23 and Figure 24 In the elastic wave filter 50 of Embodiments 1-2 shown, the frame electrodes 33 of all elastic wave resonators 10 (i.e., series arm resonators 61, 62, 63, 64 and parallel arm resonators 65, 66, 67) have a concave-convex shape in the planar direction. In contrast, in the elastic wave filter of Comparative Example 1, the frame electrodes of all elastic wave resonators (i.e., all series arm resonators and parallel arm resonators) are formed without a concave-convex shape and have a fixed width.

[0163] like Figure 23 and Figure 24 As shown, the elastic wave filters 50 described in Examples 1-1 and 1-2 exhibit lower loss at the low-frequency end of the passband (n77 band (3300MHz) indicated by arrow A1) compared to Comparative Example 1. The elastic wave filter described in Example 1-1 shows even lower loss compared to Example 1-2. Specifically, in the n77 band (3300MHz), Example 1-1 shows a loss of 1.804dB, Example 1-2 shows a loss of 1.908dB, and Comparative Example 1 shows a loss of 2.035dB.

[0164] Based on the above results, it is shown that by using a passband with a larger elastic wave filter 50 (refer to...) Figure 18 , 23 In the elastic wave resonator 10 (e.g., series arm resonators 61, 62, 63, 64) with a high resonant frequency fr at the low-frequency end of the passband (arrow A1), a frame electrode 33 with a concave-convex shape in the planar direction is provided, which can suppress the loss at the low-frequency end of the passband.

[0165] Furthermore, it is shown that by using frame electrodes 33 with concave and convex shapes in the planar direction in the series arm resonators 61, 62, 63, and 64, and using frame electrodes 33 without concave and convex shapes in the parallel arm resonators 65, 66, and 67, the loss at the low-frequency end of the passband can be effectively suppressed compared to the case where frame electrodes 33 without concave and convex shapes in the planar direction and with a fixed width are used in all elastic wave resonators 10.

[0166] In Embodiment 1-1 described above, all series arm resonators 61, 62, 63, and 64 use frame electrodes 33 with concave-convex shapes in the planar direction. Similarly, in Embodiment 1-2, all elastic wave resonators 10 use frame electrodes 33 with concave-convex shapes in the planar direction, but this is not a limitation. Frame electrodes 33 with concave-convex shapes in the planar direction may also be used in at least one elastic wave resonator 10 of the elastic wave filter 50.

[0167] Figure 25 This is a coordinate graph showing the vicinity of the passband of the elastic wave filter involved in Examples 1-3 and Comparative Example 1. Figure 26 This is a coordinate graph showing the vicinity of the passband of the elastic wave filter involved in Examples 1-4 and Comparative Example 1.

[0168] exist Figure 25 In the elastic wave filter 50 shown in Embodiments 1-3, the series arm resonator 62 (resonator s2, refer to) has the highest impedance among the series arm resonators 61, 62, 63, and 64. Figure 19 The series arm resonators 61, 63, 64 and the parallel arm resonators 65, 66, 67 are provided with frame electrodes 33 that do not have a concave-convex shape and have a fixed width.

[0169] exist Figure 26 In the elastic wave filter 50 shown in Embodiments 1-4, the series arm resonator 61 (resonator s1, refer to) has the lowest impedance among the series arm resonators 61, 62, 63, and 64. Figure 19The series arm resonators 62, 63, 64 and the parallel arm resonators 65, 66, 67 are provided with frame electrodes 33 that do not have a concave-convex shape and have a fixed width.

[0170] like Figure 25 and Figure 26 As shown, the elastic wave filter 50 described in Examples 1-3 and 1-4 exhibits lower loss at the low-frequency end of the passband compared to Comparative Example 1. Specifically, in the n77 band (3300MHz), Examples 1-3 show a loss of 1.922dB, Examples 1-4 show a loss of 2.027dB, and Comparative Example 1 shows a loss of 2.035dB. Therefore, the elastic wave filter 50 demonstrates that even when one of the series arm resonators 62 (or series arm resonator 61) of the plurality of elastic wave resonators 10 is provided with a frame electrode 33 having a concave-convex shape in the planar direction, the loss can be reduced.

[0171] Furthermore, when comparing Embodiments 1-3 with Embodiments 1-4, it is shown that the series arm resonator 62 (resonator s2) with the highest impedance among the series arm resonators 61, 62, 63, and 64 is effective in reducing losses by using a frame electrode 33 with a concave-convex shape in the planar direction.

[0172] (Example 2)

[0173] In Embodiment 2, the characteristics of the elastic wave resonator 10, which constitutes the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67, are described with respect to the resonator characteristics when a frame electrode 33 with a concave-convex shape in the planar direction is provided.

[0174] Figure 27 This is a top view showing the structure of the elastic wave resonator involved in Embodiment 2. Figure 28 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-2. Figure 29 Table 2 is a coordinate graph showing the relationship between the real part of the impedance and frequency of the elastic wave resonators involved in Embodiments 2-1 and 2-2. Table 2 shows a structural example of the elastic wave resonator involved in Embodiment 2-1. It should be noted that in Figure 28 , 29 This includes deviations in resonator characteristics caused by processing errors in the manufacturing process.

[0175] [Table 2]

[0176]

[0177] like Figure 27As shown in Table 2, the upper electrode 31 of the elastic wave resonator 10 involved in Embodiments 2-1 and 2-2 is circular. The length Wx1, Wy1 and area S of the upper electrode 31 involved in Embodiment 2-1 are equal to the length Wx1, Wy1 and area S of the upper electrode 31 involved in Embodiment 2-2.

[0178] In the elastic wave resonator 10 described in Embodiment 2-1, the first width FW1 (FWx1, FWy1) of the first portion 33a of the frame electrode 33 is 1.20 μm. The second width FW2 (FWx2, FWy2) of the second portion 33b of the frame electrode 33 is 1.40 μm. The width ratio RW of the frame electrode 33 is 16.67%, and the length ratio RL of the frame electrode 33 is 58.0.

[0179] In the elastic wave resonator 10 according to Embodiment 2-2, the frame electrode 33 does not have a concave-convex shape. That is, in the elastic wave resonator 10 according to Embodiment 2-2, the second width FW2 of the frame electrode 33 is equal to the first width FW1, and the ratio of the width RW and the ratio of the length RL of the frame electrode 33 are both 0.

[0180] like Figure 28 As shown, the impedances of the elastic wave resonators 10 involved in Embodiments 2-1 and 2-2 are almost identical. However, compared with Embodiment 2-2, the elastic wave resonator 10 of Embodiment 2-1, which uses a frame electrode 33 with a concave-convex shape in the planar direction, has a smaller impedance near the anti-resonance frequency fa, and the anti-resonance frequency fa is shifted to the high-frequency side.

[0181] like Figure 29 As shown, compared to Example 2-2, the elastic wave resonator 10 in Example 2-1 has a smaller real part (resistive component) of impedance in the frequency band (approximately 0.8fr to fr) lower than the resonant frequency fr where the boundary ring mode occurs. Especially in the frequency band lower than the resonant frequency fr, the real part of impedance in Example 2-2 is larger than that in Example 2-1. Specifically, in Example 2-1, at a frequency of 0.8fr (fr = 3903 MHz), Re(Z) = 2.49 Ω, and at a frequency of 0.9fr (fr = 3903 MHz), Re(Z) = 1.01 Ω. In Example 2-2, at a frequency of 0.8fr (fr = 3903 MHz), Re(Z) = 5.36 Ω, and at a frequency of 0.9fr (fr = 3903 MHz), Re(Z) = 2.84 Ω.

[0182] As described above, in Embodiment 2-2, a frame electrode 33 without a concave or convex shape and with a fixed width is provided. Therefore, the standing wave residing in the planar direction is concentrated at a predetermined frequency, resulting in loss. In contrast, in Embodiment 2-1, a frame electrode 33 with a concave or convex shape is shown. Therefore, the standing wave residing in the planar direction is dispersed along the frequency axis, suppressing loss.

[0183] Furthermore, the elastic wave resonator 10 of Embodiment 2-1 has a Qa value of 263 at the anti-resonance frequency fa. Additionally, the elastic wave resonator 10 of Embodiment 2-1 has a Qc value of 317 at the center frequency fc between the resonant frequency fr and the anti-resonance frequency fa. The elastic wave resonator 10 of Embodiment 2-2 has a Qa value of 298. Additionally, the elastic wave resonator 10 of Embodiment 2-2 has a Qc value of 362.

[0184] The elastic wave resonator 10 of Embodiment 2-2 is provided with a frame electrode 33 that has no concave or convex shape and has a fixed width. Therefore, compared with Embodiment 2-1, which has a frame electrode 33 with a concave or convex shape, it can better confine energy within the excitation region. As a result, compared with Embodiment 2-1, the elastic wave resonator 10 of Embodiment 2-2, which has a frame electrode 33 without a concave or convex shape, has a larger Qa at the anti-resonance frequency fa and a larger Qc at the center frequency fc.

[0185] Based on the above results, it is preferable that the series arm resonators 61, 62, 63, and 64 in the elastic wave resonator 10 constituting the elastic wave filter 50 are provided with frame electrodes 33 having concave-convex shapes in the planar direction, while the parallel arm resonators 65, 66, and 67 are provided with frame electrodes 33 without concave-convex shapes. Therefore, the elastic wave filter 50 can suppress losses on the lower frequency side of the passband and improve Qa at the anti-resonant frequency fa.

[0186] (Example 3)

[0187] In Embodiment 3, the characteristics of the elastic wave resonator 10 constituting the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67 are described with respect to the resonator characteristics when the ratio of the width of the frame electrode 33 to RW (refer to Equation (1)) is different.

[0188] Figure 30 This is a coordinate graph showing the relationship between the impedance and frequency of the elastic wave resonator involved in Embodiment 3. Figure 31 This is a coordinate graph showing the relationship between the real part of the impedance and the frequency of the elastic wave resonator involved in Embodiment 3. Figure 32This is a coordinate graph showing the relationship between the real part of the impedance of the elastic wave resonator involved in Embodiment 3 and the width of the frame electrode. Figure 33 This is a coordinate graph showing the relationship between the Q-value and the width of the frame electrode of the elastic wave resonator involved in Embodiment 3. It should be noted that... Figures 30 to 33 This includes deviations in resonator characteristics caused by processing errors in the manufacturing process.

[0189] Table 3 shows the first width FW1 (FWx1, FWy1), the second width FW2 (FWx2, FWy2), the width difference (FW2-FW1), the width ratio RW, the length ratio RL, the real part of the impedance Re(Z), and Qr, Qc, Qa of the frame electrodes of the elastic wave resonator involved in Embodiment 3. In Table 3, Qr represents Q at the resonant frequency fr.

[0190] [Table 3]

[0191]

[0192] As shown in Table 3, the elastic wave resonator 10 involved in Embodiment 3-1 is provided with a frame electrode 33 that does not have a concave or convex shape and has a fixed width. That is, the first width FW1 and the second width FW2 of Embodiment 3-1 are both 1.20 μm, and the width ratio RW and the length ratio RL are both 0.

[0193] In the elastic wave resonator 10 described in Examples 3-2 to 3-7, the first width FW1 of the first portion 33a of the frame electrode 33 is set to 1.20 μm and fixed, while the second width FW2 of the second portion 33b varies between 1.25 μm and 2.00 μm. In Examples 3-2 to 3-7, the ratio RW of each width varies between 4.2% and 66.7%. Furthermore, in Examples 3-2 to 3-7, the length ratio RL is 64.5% and fixed.

[0194] It should be noted that, in Figure 30 and Figure 31 In the coordinate graph shown, for ease of observation of the accompanying drawings, Examples 3-1 and 3-4 to 3-7 of Examples 3-1 to 3-7 are shown.

[0195] like Figure 30 As shown, the impedances of the elastic wave resonators 10 involved in Embodiments 3-1 and 3-4 to 3-7 are almost identical. However, compared with Embodiment 3-1, the elastic wave resonators 10 of Embodiments 3-4 to 3-7, which are provided with frame electrodes 33 having a concave-convex shape in the planar direction, have slightly smaller impedances near the anti-resonance frequency fa, and the anti-resonance frequency fa is shifted towards the high-frequency side.

[0196] like Figure 31 As shown, in the frequency band lower than the resonant frequency fr, the real part of the impedance is larger in Embodiment 3-1, which has a frame electrode 33 without a concave or convex shape, compared to Embodiments 3-4 to 3-7, which have a frame electrode 33 with a concave or convex shape in the planar direction.

[0197] like Figure 32 As shown, when the width ratio RW of the frame electrode 33 is varied, the real part Re(Z) of the impedance at frequencies lower than the resonant frequency fr (frequency 0.7fr, 0.9fr) changes. The real part Re(Z) of the impedance shows a minimum value when the width ratio RW is RW = 16.7% (Examples 3-4). In addition, the real part Re(Z) of the impedance shows an increasing trend when the width ratio RW is smaller or larger than 16.7%.

[0198] like Figure 33 As shown, even with variations in the width ratio RW, Qr at the resonant frequency fr remains almost constant. Qc at the center frequency fc and Qa at the anti-resonant frequency fa decrease as the width ratio RW increases. Qc and Qa exhibit large tilts (variable amounts) in the region where the width ratio RW is below 16.7%, and smaller tilts (variable amounts) in the region where the width ratio RW is above 33.3%. That is, as... Figure 32 and Figure 33 As shown, the real part of the impedance Re(Z) and Qc and Qa show opposite trends when the width ratio RW is larger than RW = 16.7%.

[0199] like Figure 32 As shown, within a width ratio RW of 4.2% to 66.7%, the real part Re(Z) of the impedance at frequency 0.9fr can be suppressed to below 2Ω. Furthermore, as... Figure 33 As shown, within a width ratio RW of 50.0% or less, the decrease in Qc and Qa can be suppressed, resulting in Qc and Qa being 0.8 times or more greater than those of Embodiment 3-1, which uses a frame electrode 33 without a concave-convex shape. Therefore, according to Figure 32 and Figure 33 The width ratio RW of the frame electrode 33 of the elastic wave resonator 10 is preferably 4.2% or more and 50% or less.

[0200] (Example 4)

[0201] In Example 4, the characteristics of the elastic wave resonator 10 constituting the series arm resonators 61, 62, 63, 64 and the parallel arm resonators 65, 66, 67 are explained with respect to the resonator characteristics when the ratio of the length of the frame electrode 33 to RL (refer to Equation (2)) is different.

[0202] Figure 34This is a coordinate graph showing the relationship between the real part of the impedance of the elastic wave resonator involved in Embodiment 4 and the length of the frame electrode. Figure 35 This is a coordinate graph showing the relationship between the Q-value and the length of the frame electrode of the elastic wave resonator involved in Embodiment 4. It should be noted that... Figure 34 and Figure 35 This includes deviations in resonator characteristics caused by processing errors in the manufacturing process.

[0203] Table 4 shows the first width FW1 (FWx1, FWy1), the second width FW2 (FWx2, FWy2), the width difference (FW2-FW1), the width ratio RW, the length ratio RL, the real part of the impedance Re(Z), and Qr, Qc, Qa of the frame electrode of the elastic wave resonator involved in Embodiment 4.

[0204] [Table 4]

[0205]

[0206] As shown in Table 4, the elastic wave resonator 10 involved in Examples 4-1 to 4-8 has a fixed first width FW1 of the frame electrode 33 of 1.20 μm and a fixed second width FW2 of 1.40 μm. That is, in Examples 4-1 to 4-8, the width difference (FW2-FW1) is 0.20 μm and fixed, and the width ratio RW is RW = 16.7% and fixed. In Examples 4-1 to 4-8, the length ratio RL is made to vary between 0.0% and 100%.

[0207] It should be noted that in Embodiment 4-1, a frame electrode 33 is provided with a length ratio RL of 0.0%, that is, it does not have a concave or convex shape and has a fixed first width FW1 (=1.20μm) along its outer periphery. In Embodiment 4-8, a frame electrode 33 is provided with a length ratio RL of 100.0%, that is, it does not have a concave or convex shape and has a fixed second width FW2 (=1.40μm) along its outer periphery.

[0208] like Figure 34 As shown, when the length ratio RL of the frame electrode 33 is varied, the real part Re(Z) of the impedance at frequencies lower than the resonant frequency fr (frequency 0.7fr, 0.9fr) changes. The real part Re(Z) of the impedance exhibits a minimum value when the length ratio RL is RL = 64.5% (Examples 4-5). Furthermore, the real part Re(Z) of the impedance shows a tendency to increase when the length ratio RL is smaller or larger than 64.5%.

[0209] Within a length ratio RL of 20% or more and 85% or less, the real part Re(Z) of the impedance at a frequency of 0.9fr can be suppressed to 2Ω or less. Therefore, the length ratio RL of the frame electrode 33 of the elastic wave resonator 10 is preferably 20% or more and 85% or less.

[0210] like Figure 35 As shown, even with changes in the length ratio RL, Qr at the resonant frequency fr remains almost constant. Qc at the center frequency fc and Qa at the anti-resonant frequency fa decrease as the length ratio RL increases. That is, as... Figure 34 and Figure 35 As shown, the real parts of the impedance Re(Z) and Qc and Qa show opposite trends when the length ratio RL is greater than RL = 64.5%.

[0211] In addition, such as Figure 35 As shown, within a length ratio RL of 65% or less, the decrease in Qc and Qa can be suppressed, resulting in Qc and Qa being, for example, 0.8 times or more, greater than those of the frame electrode 33 of Embodiment 4-1, which has a frame electrode 33 without a concave or convex shape and a fixed width. Therefore, according to Figure 34 and Figure 35 The length ratio of the frame electrode 33 of the elastic wave resonator 10 to RL is more preferably 20% or more and 65% or less.

[0212] (Example 5)

[0213] In the first embodiment and various embodiments described above, the structure of the frame electrode 33 including a first portion 33a and a second portion 33b with different widths has been described, but it is not limited thereto. The frame electrode 33 may also include three or more portions with different widths.

[0214] Figure 36 This is a coordinate graph showing the relationship between impedance and frequency of the elastic wave resonator involved in Embodiment 5 and Embodiments 4-5. Figure 37 This is a coordinate graph showing the relationship between the real part of the impedance and the frequency of the elastic wave resonator involved in Embodiment 5 and Embodiments 4-5.

[0215] In the elastic wave resonator 10 according to Embodiment 5, the frame electrode 33 includes a first portion 33a with a first width FW1, a second portion 33b with a second width FW2, a third portion with a third width FW3, and a fourth portion with a fourth width FW4, in addition to the first width FW1 being 1.2 μm, the second width FW2 being 1.4 μm, the third width FW3 being 1.6 μm, and the fourth width FW4 being 1.8 μm. Furthermore, the length ratio is RL = 64.5%.

[0216] In embodiment 5, the configuration is repeated periodically along the outer periphery of the frame electrode 33, such as first part 33a, second part 33b, first part 33a, third part, first part 33a, fourth part, first part 33a, second part 33b, first part 33a, third part...

[0217] It should be noted that, in Figure 36 and Figure 37 For comparison, the resonator characteristics of the elastic wave resonator 10 involved in Embodiments 4-5 are also shown. In Embodiments 4-5, the first width FW1 is 1.20 μm, the second width FW2 is 1.40 μm, the width ratio RW is RW = 16.7%, and the length ratio is RL = 64.5%.

[0218] like Figure 36 As shown, the elastic wave resonator 10 involved in Embodiment 5 has an impedance that is almost identical to that in Embodiments 4-5.

[0219] like Figure 37 As shown, compared to Examples 4-5, the real part of the impedance of the elastic wave resonator 10 in Example 5 is smaller at a lower frequency position than the resonant frequency fr. Specifically, the real part of the impedance of the elastic wave resonator 10 in Example 5 at a frequency of 0.8fr is 2.23Ω. The real part of the impedance of the elastic wave resonator 10 in Examples 4-5 at a frequency of 0.8fr is 2.49Ω.

[0220] It should be noted that in Embodiment 5, an example of periodically repeating multiple portions with different widths was described. However, this is not a limitation; multiple portions with different widths can be arbitrarily configured. For example, they can be periodically repeated along the outer periphery of the frame electrode 33, such as first portion 33a, second portion 33b, third portion, fourth portion, first portion 33a, second portion 33b, third portion, and so on. Alternatively, the configuration order of the first portion 33a to the fourth portion can be randomized. Furthermore, the multiple portions with different widths are not limited to two or four; there can be three or five or more.

[0221] (Example 6)

[0222] In Example 6, 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 38 This is a graph showing the relationship between the Euler angles and fractional bandwidth of the piezoelectric element using lithium niobate in the elastic wave resonator according to Embodiment 6-1. In the elastic wave resonator 10 according to Embodiment 6-1, lithium niobate is used as the piezoelectric element 20.

[0223] It should be noted that when the resonant frequency of the elastic wave resonator 10 is set to fr, the anti-resonant frequency is set to fa, and the frequency difference between the resonant frequency and the anti-resonant frequency is set to (fa-fr), Figure 38 The fractional bandwidth ΔfR shown is represented by ΔfR = (fa - fr) / fr.

[0224] Figure 38 The horizontal axis of the coordinate graph shown is the Euler angle θ of lithium niobate. For example... Figure 38 As indicated by arrow B1, the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element 20 are preferably in the range of (φ, θ, ψ) = (0°, 107 to 140°, 0°). Therefore, the elastic wave resonator 10 according to Embodiment 6-1 can achieve a wideband with a fractional bandwidth ΔfR of 10% or more.

[0225] In addition, such as Figure 38 As indicated by arrow B2, it is preferable to set the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric element 20 to the range of (φ, θ, ψ) = (0°, 123~139°, 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 Example 6-1 can reduce unwanted waves caused by the transverse wave.

[0226] Figure 39 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 according to Embodiment 6-2. In the elastic wave resonator 10 according to Embodiment 6-2, lithium tantalate is used as the piezoelectric element 20.

[0227] Figure 39 The horizontal axis of the coordinate graph shown is the Euler angle θ of lithium tantalate. For example... Figure 39 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 6-2 can achieve a wideband with a fractional bandwidth ΔfR of 3% or more.

[0228] In addition, such as Figure 39 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°, 123~139°, 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 6-2 can reduce unwanted waves caused by the transverse wave.

[0229] In Example 6-1, 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 6-2, 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 6-1 and 6-2, in the elastic wave resonator 10 where aluminum nitride (AlN) is used as the material for the piezoelectric element 20, the longitudinal wave is typically used as the fundamental mode, and the longitudinal piezoelectric constant e is... 33 It is approximately 1.515. Therefore, the longitudinal piezoelectric constant e is approximately 1.515 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, thus resulting in a wideband resonator.

[0230] The structures of the above embodiments can be appropriately combined. In addition, the specific structures and values ​​of each embodiment (e.g., the shape of the upper electrode 31, the first width FW1 and the second width FW2 of the frame electrode 33, the area S of each electrode, etc.) are merely examples and are not limited thereto.

[0231] (Second Implementation)

[0232] Figure 40 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, 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.

[0233] like Figure 40 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.

[0234] 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.

[0235] 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 are 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.

[0236] Specifically, the high-frequency front-end circuit 101 includes a switch SW, power amplifiers 111a and 111b, matching circuits 112a and 112b, transmitting filters 113a and 113b, a multiplexer 114, matching circuits 115a and 115b, and low-noise amplifiers 116a and 116b.

[0237] 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 input to transmit filter 113a or transmit filter 113b through matching circuits 112a and 112b.

[0238] 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.

[0239] The high-frequency transmission signal that has passed through transmission filter 113a or transmission filter 113b is supplied to antenna 102.

[0240] 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 each of the multiple receive filters 117a and 117b are electrically connected through 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.

[0241] 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.

[0242] 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 the receiving filters 117a and 117b of the multiplexer 114. Additionally, the communication device 100 includes the high-frequency front-end circuit 101.

[0243] It should be noted that, Figure 40 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; 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 in the multiplexer 114 can have their output terminals electrically connected to each other depending on the mounted device.

[0244] It should be noted that the above embodiments are intended to facilitate understanding of the present invention and are not intended to limit the interpretation of the present invention. The present invention can be modified / improved without departing from its spirit, and its equivalents are also included in the present invention.

[0245] It should be noted that this disclosure can also adopt the following structure.

[0246] (1) An elastic wave filter comprising a plurality of elastic wave resonators utilizing body waves, wherein,

[0247] The plurality of elastic wave resonators each have:

[0248] piezoelectric elements;

[0249] The upper electrode is disposed on the piezoelectric body;

[0250] The lower electrode is disposed below the piezoelectric element; and

[0251] A frame electrode, which is frame-shaped along the outer periphery of at least one of the upper electrode and the lower electrode.

[0252] The frame electrode of at least one of the plurality of elastic wave resonators includes a plurality of first portions and a plurality of second portions having a width or height larger than the plurality of first portions.

[0253] The plurality of first portions and the plurality of second portions are arranged alternately in a direction along the outer periphery.

[0254] (2) According to the elastic wave filter described in (1), where,

[0255] The elastic wave resonator among the plurality of elastic wave resonators having a resonant frequency higher than the low-frequency end of the passband has the frame electrode comprising the plurality of first portions and the plurality of second portions.

[0256] (3) The elastic wave filter described in (1) or (2), wherein,

[0257] The elastic wave filter has a series arm resonator and a parallel arm resonator constructed using the elastic wave resonator.

[0258] The frame electrode of the series arm resonator is configured to include the plurality of first portions and the plurality of second portions.

[0259] The frame electrode of the parallel arm resonator does not have the plurality of first portions and the plurality of second portions, and has a fixed width or a fixed height along the outer periphery.

[0260] (4) The elastic wave filter according to any one of (1) to (3), wherein,

[0261] The elastic wave filter has multiple series-arm resonators constructed using the elastic wave resonator.

[0262] The series arm resonator with the highest impedance among the plurality of series arm resonators has the frame electrode comprising the plurality of first portions and the plurality of second portions.

[0263] (5) The elastic wave filter according to any one of (1) to (4), wherein,

[0264] In the frame electrodes of the at least one elastic wave resonator, the plurality of first portions have a first width (FW1), and the plurality of second portions have a second width (FW2) that is larger than the first width.

[0265] When the ratio of the difference between the first width and the second width to the first width is defined as the width ratio (RW), the width ratio (RW) is expressed as RW = ((FW2 - FW1) / FW1) × 100%.

[0266] The width ratio (RW) is 4.2% or more and 50% or less.

[0267] (6) The elastic wave filter according to any one of (1) to (5), wherein,

[0268] When the ratio of the total length of the frame electrodes along the outer periphery to the total length of the plurality of second portions along the outer periphery is set as the length ratio,

[0269] The ratio of the lengths is more than 20% and less than 85%.

[0270] (7) The elastic wave filter according to any one of (1) to (6), wherein,

[0271] The elastic wave filter further includes a plurality of third parts, each having a wider or higher width than the plurality of second parts.

[0272] The plurality of first portions, the plurality of second portions, and the plurality of third portions are arranged periodically along the periphery.

[0273] (8) The elastic wave filter according to any one of (1) to (7), wherein,

[0274] In the frame electrodes of the at least one elastic wave resonator, the plurality of first portions have a first width, and the plurality of second portions have a second width larger than the first width.

[0275] The plurality of second portions are disposed protruding toward the inner periphery of the frame electrode compared to the plurality of first portions.

[0276] The frame electrode has an uneven shape along its inner periphery in the planar direction.

[0277] (9) The elastic wave filter according to any one of (1) to (8), wherein,

[0278] The piezoelectric element includes lithium niobate or lithium tantalate.

[0279] (10) The elastic wave filter according to any one of (1) to (8), wherein,

[0280] The piezoelectric element includes lithium niobate.

[0281] 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°).

[0282] (11) The elastic wave filter according to any one of (1) to (8), wherein,

[0283] The piezoelectric element includes lithium niobate.

[0284] 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°).

[0285] (12) The elastic wave filter according to any one of (1) to (8), wherein,

[0286] The piezoelectric element includes lithium tantalate.

[0287] 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°).

[0288] (13) The elastic wave filter according to any one of (1) to (8), wherein,

[0289] The piezoelectric element includes lithium tantalate.

[0290] The Euler angles (φ, θ, ψ) of the lithium tantalate constituting the piezoelectric element are in the range of (φ, θ, ψ) = (0°, 123~134°, 0°).

[0291] (14) An elastic wave filter comprising a plurality of elastic wave resonators utilizing body waves, wherein,

[0292] The plurality of elastic wave resonators each have:

[0293] piezoelectric elements;

[0294] The upper electrode is disposed on the piezoelectric body;

[0295] The lower electrode is disposed below the piezoelectric element; and

[0296] A frame electrode, disposed along the outer periphery of at least one of the upper electrode and the lower electrode, is used to add mass.

[0297] The frame electrode of the elastic wave resonator having a resonant frequency higher than the low-frequency end of the passband in the plurality of elastic wave resonators includes a plurality of first portions and a plurality of second portions having a width or height greater than the first portions.

[0298] The plurality of first portions and the plurality of second portions are arranged alternately in a direction along the outer periphery.

[0299] (15) A multiplexer having a plurality of filters, the plurality of filters including the elastic wave filters described in any one of (1) to (14),

[0300] The input and output terminals of each of the plurality of filters are electrically connected to each other.

[0301] (16) A high-frequency front-end circuit having an elastic wave filter described in any one of (1) to (14).

[0302] (17) A high-frequency front-end circuit having the multiplexer described in (15).

[0303] (18) A communication device having the high-frequency front-end circuit described in (16) or (17).

[0304] Explanation of reference numerals in the attached figures

[0305] 10: Elastic wave resonator

[0306] 11: Support base plate

[0307] 12: Intermediate layer

[0308] 13: Supporting components

[0309] 14, 14a, 14b: concave part

[0310] 20: Piezoelectric element

[0311] 20a: First Main Page

[0312] 20b: Second Main Page

[0313] 31: Upper electrode

[0314] 32: Lower electrode

[0315] 33, 33A, 33B, 33C, 33D: Frame electrodes

[0316] 33a, 33Aa, 33Ba, 33Ca, 33Da: Part 1

[0317] 33b, 33Ab, 33Bb, 33Cb, 33Db: Part Two

[0318] 34, 35: Outgoing wiring

[0319] 50: Elastic wave filter

[0320] 51: Resonator Chip

[0321] 52: Module baseboard

[0322] 61, 61A, 62, 63, 64: Series arm resonators

[0323] 65, 66, 67: Parallel arm resonators

[0324] 100: Communication device

[0325] 101: High-frequency front-end circuit

[0326] Wx1, Wy1: Length

[0327] FW1, FWx1, FWy1: First width

[0328] FW2, FWx2, FWy2: Second width

[0329] FH1: First Height

[0330] FH2: Second Altitude

[0331] FL1: First Length

[0332] FL2: Second length.

Claims

1. An elastic wave filter comprising a plurality of elastic wave resonators utilizing body waves, wherein, The plurality of elastic wave resonators each have: piezoelectric elements; The upper electrode is disposed on the piezoelectric body; The lower electrode is disposed below the piezoelectric element; and A frame electrode, which is frame-shaped along the outer periphery of at least one of the upper electrode and the lower electrode. The frame electrode of at least one of the plurality of elastic wave resonators includes a plurality of first portions and a plurality of second portions having a width or height larger than the plurality of first portions. The plurality of first portions and the plurality of second portions are arranged alternately in a direction along the outer periphery.

2. The elastic wave filter according to claim 1, wherein, The elastic wave resonator among the plurality of elastic wave resonators having a resonant frequency higher than the low-frequency end of the passband has the frame electrode comprising the plurality of first portions and the plurality of second portions.

3. The elastic wave filter according to claim 1 or 2, wherein, The elastic wave filter has a series arm resonator and a parallel arm resonator constructed using the elastic wave resonator. The frame electrode of the series arm resonator is configured to include the plurality of first portions and the plurality of second portions. The frame electrode of the parallel arm resonator does not have the plurality of first portions and the plurality of second portions, and has a fixed width or a fixed height along the outer periphery.

4. The elastic wave filter according to any one of claims 1 to 3, wherein, The elastic wave filter has multiple series-arm resonators constructed using the elastic wave resonator. The series arm resonator with the highest impedance among the plurality of series arm resonators has the frame electrode comprising the plurality of first portions and the plurality of second portions.

5. The elastic wave filter according to any one of claims 1 to 4, wherein, In the frame electrodes of the at least one elastic wave resonator, the plurality of first portions have a first width FW1, and the plurality of second portions have a second width FW2 that is larger than the first width. When the ratio of the difference between the first width and the second width to the first width is defined as the width ratio RW, the width ratio RW is expressed as RW = ((FW2 - FW1) / FW1) × 100%. The width ratio RW is 4.2% or more and 50% or less.

6. The elastic wave filter according to any one of claims 1 to 5, wherein, When the ratio of the total length of the frame electrodes along the outer periphery to the total length of the plurality of second portions along the outer periphery is set as the length ratio, The ratio of the lengths is more than 20% and less than 85%.

7. The elastic wave filter according to any one of claims 1 to 6, wherein, The elastic wave filter further includes a plurality of third parts, each having a wider or higher width than the plurality of second parts. The plurality of first portions, the plurality of second portions, and the plurality of third portions are arranged periodically along the periphery.

8. The elastic wave filter according to any one of claims 1 to 7, wherein, In the frame electrodes of the at least one elastic wave resonator, the plurality of first portions have a first width, and the plurality of second portions have a second width larger than the first width. The plurality of second portions are disposed protruding toward the inner periphery of the frame electrode compared to the plurality of first portions. The frame electrode has an uneven shape along its inner periphery in the planar direction.

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

10. The elastic wave filter according to any one of claims 1 to 8, wherein, The piezoelectric element includes 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°).

11. The elastic wave filter according to any one of claims 1 to 8, wherein, The piezoelectric element includes 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°).

12. The elastic wave filter according to any one of claims 1 to 8, wherein, The piezoelectric element includes 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°).

13. The elastic wave filter according to any one of claims 1 to 8, wherein, The piezoelectric element includes 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°, 123~134°, 0°).

14. An elastic wave filter comprising a plurality of elastic wave resonators utilizing body waves, wherein, The plurality of elastic wave resonators each have: piezoelectric elements; The upper electrode is disposed on the piezoelectric body; The lower electrode is disposed below the piezoelectric element; and A frame electrode, disposed along the outer periphery of at least one of the upper electrode and the lower electrode, is used to add mass. The frame electrode of the elastic wave resonator having a resonant frequency higher than the low-frequency end of the passband in the plurality of elastic wave resonators includes a plurality of first portions and a plurality of second portions having a width or height greater than the first portions. The plurality of first portions and the plurality of second portions are arranged alternately in a direction along the outer periphery.

15. A multiplexer having a plurality of filters, the plurality of filters including the elastic wave filter according to any one of claims 1 to 14. The input and output terminals of each of the plurality of filters are electrically connected to each other.

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

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

18. A communication device comprising the high-frequency front-end circuit as described in claim 16 or 17.

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