Elastic wave device

Abstract

An elastic wave device includes: a resonator including a piezoelectric layer having a first main surface and a second main surface on an opposite side to the first main surface, an upper electrode provided on the first main surface of the piezoelectric layer, and a lower electrode provided on the second main surface of the piezoelectric layer; and a capacitor element including an upper IDT electrode provided on the first main surface of the piezoelectric layer and a lower IDT electrode provided on the second main surface of the piezoelectric layer, the capacitor element being connected in parallel with the resonator, and the upper IDT electrode and the lower IDT electrode of the capacitor element being electrically connected.

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Patent Document 1 describes an elastic wave device that utilizes a bulk acoustic wave (BAW) element. The elastic wave device of Patent Document 1 includes a Lamb wave loop circuit that generates a Lamb wave with the opposite phase to a target signal at a specific frequency. The Lamb wave loop circuit includes an IDT electrode.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2019 / 0273478 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In such elastic wave devices, miniaturization and good tuning of transmission characteristics are required. In Patent Document 1, the IDT electrodes of the Lamb wave loop circuit are provided for exciting the Lamb wave, without considering the formation of a given electrostatic capacitance through the IDT electrodes of the Lamb wave loop circuit.

[0008] The object of the present invention is to provide an elastic wave device that can be miniaturized and has well-adjusted transmission characteristics.

[0009] Technical solutions for solving the problem

[0010] One approach relates to an elastic wave device comprising: a resonator including a piezoelectric layer having a first main surface and a second main surface opposite to the first main surface, an upper electrode disposed on the first main surface of the piezoelectric layer, and a lower electrode disposed on the second main surface of the piezoelectric layer; and a capacitor element including an upper IDT (Interdigital Transducer) electrode disposed on the first main surface of the piezoelectric layer, and a lower IDT electrode disposed on the second main surface of the piezoelectric layer, the capacitor element being connected in parallel with the resonator, and the upper IDT electrode and the lower IDT electrode of the capacitor element being electrically connected.

[0011] Invention Effects

[0012] The elastic wave device according to the present invention can be miniaturized and its transmission characteristics can be well adjusted. Attached Figure Description

[0013] Figure 1 This is a perspective view showing the elastic wave device according to the first embodiment.

[0014] Figure 2 yes Figure 1 Sectional view II-II'.

[0015] Figure 3 This is an explanatory diagram illustrating the capacitor formed in the capacitor element according to the first embodiment.

[0016] Figure 4 This is a cross-sectional view showing the elastic wave device according to the second embodiment.

[0017] Figure 5 This is an explanatory diagram illustrating the capacitor formed in the capacitor element according to the second embodiment.

[0018] Figure 6 This is a circuit diagram showing the elastic wave device according to the third embodiment.

[0019] Figure 7 The graphs show the transmission characteristics of the elastic wave devices involved in Embodiment 1 and Comparative Examples 1 and 2.

[0020] Figure 8 This is a circuit diagram showing the elastic wave device according to the fourth embodiment.

[0021] Figure 9 The graphs show the transmission characteristics of the elastic wave devices involved in Embodiment 2 and Comparative Examples 1 and 3. Detailed Implementation

[0022] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. However, the present disclosure is not limited to these embodiments. Furthermore, the embodiments described in this disclosure are exemplary, and partial substitutions or combinations of structures can be made between different embodiments. From the modified examples and the second embodiment onwards, descriptions of matters common to the first embodiment are omitted, and only the differences are described. In particular, the same effects resulting from the same structure are not mentioned repeatedly in each embodiment.

[0023] (First Embodiment)

[0024] Figure 1 This is a perspective view showing the elastic wave device according to the first embodiment. Figure 2 yes Figure 1 Sectional view II-II'. (See also...) Figure 1 as well as Figure 2As shown, the elastic wave device 10 includes a support member 13, a piezoelectric layer 20, a resonator 30, and a capacitor element 40. The resonator 30 is a bulk wave resonator, i.e., a BAW (Bulk Acoustic Wave) element. Furthermore, the capacitor element 40 is configured to have IDT (Interdigital Transducer) electrodes.

[0025] In the following description, the thickness direction of the piezoelectric layer 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 layer 20. Furthermore, in the following description, "top view" refers to the arrangement when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric layer 20 (Z direction).

[0026] The support member 13 is positioned opposite the second main surface 20b of the piezoelectric layer 20. The support member 13 includes a support substrate 11 and an insulating layer 12. The support substrate 11 comprises silicon (Si), quartz, or the like. The insulating layer 12 is disposed between the support substrate 11 and the piezoelectric layer 20. The insulating layer 12 is formed of an insulating material such as silicon oxide. Alternatively, the support member 13 may also have a structure in which the piezoelectric layer 20 is disposed on the support substrate 11 without the insulating layer 12. A close-fitting layer such as Ti or NiCr may also exist between the lower electrode 32 and the insulating layer 12.

[0027] like Figure 2 As shown, a cavity 14 (void) is formed on the surface of the support member 13 (insulating layer 12) opposite to the second main surface 20b of the piezoelectric layer 20. The cavity 14 is configured to overlap with the excitation region of the resonator 30, which is composed of the piezoelectric layer 20, the upper electrode 31, and the lower electrode 32, when viewed from above. As a result, bulk waves are reflected through the cavity 14.

[0028] The piezoelectric layer 20 is a flat plate having a first main surface 20a and a second main surface 20b opposite to the first main surface 20a. The piezoelectric layer 20 is a substrate containing a single crystal of lithium niobate (LiNbO3) or lithium tantalate (LiTaO3). The thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 1 μm or less.

[0029] like Figure 1 as well as Figure 2 As shown, the resonator 30 includes a piezoelectric layer 20, an upper electrode 31 disposed on a first main surface 20a of the piezoelectric layer 20, and a lower electrode 32 disposed on a second main surface 20b of the piezoelectric layer 20. The resonator 30 is constructed by sequentially stacking the lower electrode 32, the piezoelectric layer 20, and the upper electrode 31 on the support member 13.

[0030] The resonator 30 has a so-called diaphragm structure in which a cavity 14 (void) is provided on the second main surface 20b side of the piezoelectric layer 20. For example... Figure 2 As shown, in the region overlapping with cavity 14, a piezoelectric layer 20 is disposed between the upper electrode 31 and the lower electrode 32 in the Z direction. Thus, volume waves propagate between the upper electrode 31 and the lower electrode 32.

[0031] The upper electrode 31 and the lower electrode 32 are formed of metals such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), and molybdenum (Mo), or alloys containing at least one of these materials. The upper electrode 31 and the lower electrode 32 may also be a laminated film.

[0032] like Figure 1 As shown, the upper electrode 31 and the lower electrode 32 are rectangular in shape when viewed from above. However, they are not limited to this shape; the upper electrode 31 and the lower electrode 32 can also be circular, polygonal, or other shapes.

[0033] The capacitor element 40 includes an upper IDT electrode 41 disposed on the first main surface 20a of the piezoelectric layer 20 and a lower IDT electrode 42 disposed on the second main surface 20b of the piezoelectric layer 20. The upper IDT electrode 41 is disposed in the same layer as the upper electrode 31 constituting the resonator 30. Furthermore, the lower IDT electrode 42 is disposed in the same layer as the lower electrode 32 constituting the resonator 30.

[0034] The upper IDT electrode 41 and the lower IDT electrode 42 are electrically connected through a first via 35 and a second via 36, ​​which are configured to penetrate the piezoelectric layer 20. Furthermore, the capacitor element 40 is connected in parallel with the resonator 30. That is, one end of the capacitor element 40 is connected to the upper electrode 31 via a connection wiring 33. The other end of the capacitor element 40 is connected to the lower electrode 32 via a connection wiring 34.

[0035] More specifically, the upper IDT electrode 41 has a first electrode finger 43A, a second electrode finger 44A, a first busbar electrode 45A, and a second busbar electrode 46A. A plurality of first electrode fingers 43A extend in the Y direction, with one end connected to the first busbar electrode 45A. A plurality of second electrode fingers 44A extend in the Y direction, with the other end connected to the second busbar electrode 46A. The plurality of first electrode fingers 43A and the plurality of second electrode fingers 44A are alternately arranged at intervals in the X direction. The first busbar electrode 45A and the second busbar electrode 46A extend in the X direction and are separately configured in the Y direction. The plurality of first electrode fingers 43A and the plurality of second electrode fingers 44A are arranged between the first busbar electrode 45A and the second busbar electrode 46A.

[0036] The lower IDT electrode 42 has a third electrode finger 43B, a fourth electrode finger 44B, a third bus electrode 45B, and a fourth bus electrode 46B. The plurality of third electrode fingers 43B extend in the Y direction, with one end connected to the third bus electrode 45B. The plurality of fourth electrode fingers 44B extend in the Y direction, with the other end connected to the fourth bus electrode 46B. The plurality of third electrode fingers 43B and the plurality of fourth electrode fingers 44B are alternately arranged in the X direction at intervals. The third bus electrode 45B and the fourth bus electrode 46B extend in the X direction and are separately configured in the Y direction. The plurality of third electrode fingers 43B and the plurality of fourth electrode fingers 44B are arranged between the third bus electrode 45B and the fourth bus electrode 46B.

[0037] In this embodiment, a plurality of first electrode fingers 43A of the upper IDT electrode 41 are arranged overlappingly with a plurality of third electrode fingers 43B of the lower IDT electrode 42, and extend in the same direction as the extending direction of the plurality of third electrode fingers 43B. A plurality of second electrode fingers 44A of the upper IDT electrode 41 are arranged overlappingly with a plurality of fourth electrode fingers 44B of the lower IDT electrode 42, and extend in the same direction as the extending direction of the plurality of fourth electrode fingers 44B.

[0038] Furthermore, in the following description, when it is not necessary to distinguish between the first electrode finger 43A, the second electrode finger 44A, the third electrode finger 43B, and the fourth electrode finger 44B, they may sometimes be referred to simply as electrode fingers. Additionally, when it is not necessary to distinguish between the first busbar electrode 45A, the second busbar electrode 46A, the third busbar electrode 45B, and the fourth busbar electrode 46B, they may sometimes be referred to simply as busbar electrodes.

[0039] One end of the connection wiring 33, located on the first main surface 20a of the piezoelectric layer 20, is connected to the upper electrode 31, and the other end of the connection wiring 33 is connected to the first busbar electrode 45A. Furthermore, one end of the connection wiring 37, located on the second main surface 20b of the piezoelectric layer 20, is connected to the connection wiring 33 via a first via 35. The other end of the connection wiring 37 is connected to the third busbar electrode 45B.

[0040] Thus, the first electrode finger 43A of the upper IDT electrode 41 and the third electrode finger 43B of the lower IDT electrode 42 are electrically connected via the connecting wiring 33, the first via 35, and the connecting wiring 37. Furthermore, the plurality of first electrode fingers 43A of the upper IDT electrode 41 and the plurality of third electrode fingers 43B of the lower IDT electrode 42 are electrically connected to the upper electrode 31 of the resonator 30 via the connecting wiring 33, the first via 35, and the connecting wiring 37. Thus, the same potential is supplied to the first electrode fingers 43A of the upper IDT electrode 41 and the third electrode fingers 43B of the lower IDT electrode 42.

[0041] Similarly, one end of the connection wiring 34 provided on the second main surface 20b of the piezoelectric layer 20 is connected to the lower electrode 32, and the other end of the connection wiring 34 is connected to the fourth busbar electrode 46B. Furthermore, one end of the connection wiring 38 provided on the first main surface 20a of the piezoelectric layer 20 is connected to the connection wiring 34 through the second via 36. The other end of the connection wiring 38 is connected to the second busbar electrode 46A.

[0042] Therefore, the second electrode finger 44A of the upper IDT electrode 41 and the fourth electrode finger 44B of the lower IDT electrode 42 are electrically connected via the connecting wiring 34, the second via 36, ​​and the connecting wiring 38. Furthermore, the plurality of second electrode fingers 44A of the upper IDT electrode 41 and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42 are electrically connected to the lower electrode 32 of the resonator 30 via the connecting wiring 34, the second via 36, ​​and the connecting wiring 38. Thus, the second electrode fingers 44A of the upper IDT electrode 41 and the fourth electrode fingers 44B of the lower IDT electrode 42 are supplied with the same potential. Furthermore, the first electrode finger 43A of the upper IDT electrode 41 and the third electrode finger 43B of the lower IDT electrode 42 are supplied with different potentials than the second electrode fingers 44A of the upper IDT electrode 41 and the fourth electrode fingers 44B of the lower IDT electrode 42.

[0043] Furthermore, the connection relationship between the upper IDT electrode 41 and the lower IDT electrode 42 of the capacitor element 40 and the upper electrode 31 and the lower electrode 32 of the resonator 30 is not limited to the above structure. Alternatively, the plurality of first electrode fingers 43A of the upper IDT electrode 41 and the plurality of third electrode fingers 43B of the lower IDT electrode 42 may be electrically connected to the lower electrode 32 of the resonator 30, and the plurality of second electrode fingers 44A of the upper IDT electrode 41 and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42 may be electrically connected to the upper electrode 31 of the resonator 30.

[0044] like Figure 2As shown, the plurality of first electrode fingers 43A of the upper IDT electrode 41 and the plurality of third electrode fingers 43B of the lower IDT electrode 42 are electrically connected and are arranged opposite each other in the Z direction, sandwiching the piezoelectric layer 20. As described above, the plurality of first electrode fingers 43A of the upper IDT electrode 41 and the plurality of third electrode fingers 43B of the lower IDT electrode 42, which are arranged opposite each other in the Z direction, are supplied with the same potential.

[0045] The plurality of second electrode fingers 44A of the upper IDT electrode 41 and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42 are electrically connected and are arranged opposite each other in the Z direction, sandwiching a piezoelectric layer 20. As described above, the plurality of second electrode fingers 44A of the upper IDT electrode 41 and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42, which are arranged opposite each other in the Z direction, are supplied with the same potential. In addition, the plurality of first electrode fingers 43A and the plurality of second electrode fingers 44A of the upper IDT electrode 41 that are adjacent in the X direction are supplied with different potentials. The plurality of third electrode fingers 43B and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42 are supplied with different potentials.

[0046] Figure 3 This is an explanatory diagram illustrating the capacitor formed in the capacitor element according to the first embodiment. (As shown) Figure 3 As shown, in capacitor element 40, a capacitor Cx1 is formed between the first electrode finger 43A and the second electrode finger 44A of the upper IDT electrode 41, which are adjacent in the X direction in the same layer. Furthermore, a capacitor Cx2 is formed between the third electrode finger 43B and the fourth electrode finger 44B of the lower IDT electrode 42, which are adjacent in the X direction in the same layer. Furthermore, a capacitor Cz1 is formed between the first electrode finger 43A of the upper IDT electrode 41 and the fourth electrode finger 44B of the lower IDT electrode 42, which are sandwiched in the piezoelectric layer 20 and located in the inclined direction. Furthermore, a capacitor Cz2 is formed between the second electrode finger 44A of the upper IDT electrode 41 and the third electrode finger 43B of the lower IDT electrode 42, which are sandwiched in the piezoelectric layer 20 and located in the inclined direction.

[0047] Therefore, since the capacitor element 40 has an upper IDT electrode 41 and a lower IDT electrode 42 sandwiched between the piezoelectric layer 20, the overall capacitance of the capacitor element 40 can be increased compared to a structure that only has an upper IDT electrode 41 and a lower IDT electrode 42. Alternatively, compared to the case where only the upper IDT electrode 41 and the lower IDT electrode 42 are provided, the size (planar area) of the capacitor element 40 used to form the same capacitance can be reduced.

[0048] Since a capacitor element 40 is connected to the resonator 30, the frequency of the attenuation electrode of the resonator 30 can be appropriately adjusted. Therefore, the elastic wave device 10 can be miniaturized and its transmission characteristics can be well adjusted. Furthermore, the transmission characteristics of the resonator 30 will be described later in the third and fourth embodiments.

[0049] In addition, Figures 1 to 3 In the accompanying drawings, for ease of observation, two of each of the first electrode finger 43A and the second electrode finger 44A of the upper IDT electrode 41, and two of each of the third electrode finger 43B and the fourth electrode finger 44B of the lower IDT electrode 42 are shown. However, this is not a limitation, and each electrode finger may have three or more. The width and spacing of each electrode finger are merely examples and can be appropriately varied according to the capacitance and size (planar area) required by the capacitor element 40.

[0050] (Second Implementation)

[0051] Figure 4 This is a cross-sectional view showing the elastic wave device according to the second embodiment. (As shown) Figure 4 As shown, the elastic wave device 10A according to the second embodiment differs from the first embodiment in the arrangement of the first electrode finger 43A and the second electrode finger 44A of the upper IDT electrode 41 with the third electrode finger 43B and the fourth electrode finger 44B of the lower IDT electrode 42. Furthermore, the connection relationships between the electrode fingers of the upper IDT electrode 41 and the lower IDT electrode 42 and the upper electrode 31 and the lower electrode 32 of the resonator 30 are the same as in the first embodiment, and repeated descriptions are omitted.

[0052] Specifically, in capacitor element 40A, a plurality of first electrode fingers 43A of upper IDT electrode 41 and a plurality of fourth electrode fingers 44B of lower IDT electrode 42 are arranged opposite each other in the Z direction, sandwiching piezoelectric layer 20. A plurality of second electrode fingers 44A of upper IDT electrode 41 and a plurality of third electrode fingers 43B of lower IDT electrode 42 are arranged opposite each other in the Z direction, sandwiching piezoelectric layer 20.

[0053] In this embodiment, a plurality of first electrode fingers 43A of the upper IDT electrode 41 are arranged overlappingly with a plurality of fourth electrode fingers 44B of the lower IDT electrode 42, and extend in the same direction as the extending direction of the plurality of fourth electrode fingers 44B. A plurality of second electrode fingers 44A of the upper IDT electrode 41 are arranged overlappingly with a plurality of third electrode fingers 43B of the lower IDT electrode 42, and extend in the same direction as the extending direction of the plurality of third electrode fingers 43B.

[0054] Different potentials are supplied to the plurality of first electrode fingers 43A of the upper IDT electrode 41 and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42, which are opposite each other in the Z direction. In addition, different potentials are supplied to the plurality of second electrode fingers 44A of the upper IDT electrode 41 and the plurality of third electrode fingers 43B of the lower IDT electrode 42, which are opposite each other in the Z direction.

[0055] Furthermore, the plurality of first electrode fingers 43A of the upper IDT electrode 41 and the plurality of third electrode fingers 43B of the lower IDT electrode 42, which are electrically connected and supplied with the same potential, are arranged in a non-overlapping position. Similarly, the plurality of second electrode fingers 44A of the upper IDT electrode 41 and the plurality of fourth electrode fingers 44B of the lower IDT electrode 42, which are electrically connected and supplied with the same potential, are arranged in a non-overlapping position.

[0056] Figure 5 This is an explanatory diagram illustrating the capacitor formed in the capacitor element according to the second embodiment. (As shown...) Figure 5 As shown, in capacitor element 40A, a capacitor Cz3 is formed between the first electrode finger 43A of the upper IDT electrode 41 and the fourth electrode finger 44B of the lower IDT electrode 42, which are positioned opposite each other in the Z direction and sandwich the piezoelectric layer 20. Similarly, a capacitor Cz4 is formed between the second electrode finger 44A of the upper IDT electrode 41 and the third electrode finger 43B of the lower IDT electrode 42, which are positioned opposite each other in the Z direction and sandwich the piezoelectric layer 20.

[0057] In the second embodiment, the distance between the first electrode finger 43A of the upper IDT electrode 41 and the fourth electrode finger 44B of the lower IDT electrode 42 is shorter than that in the first embodiment. Furthermore, the distance between the second electrode finger 44A of the upper IDT electrode 41 and the third electrode finger 43B of the lower IDT electrode 42 is also shorter than that in the first embodiment. Therefore, the capacitances Cz3 and Cz4 of the capacitor element 40A are greater than the capacitances Cz1 and Cz2 of the capacitor element 40 shown in the first embodiment.

[0058] Furthermore, in the second embodiment, a capacitor Cx1 is also formed between the first electrode finger 43A and the second electrode finger 44A of the upper IDT electrode 41, which are adjacent in the X direction in the same layer. Additionally, a capacitor Cx2 is formed between the third electrode finger 43B and the fourth electrode finger 44B of the lower IDT electrode 42, which are adjacent in the X direction in the same layer. Capacitors Cx1 and Cx2 are the same as in the first embodiment described above.

[0059] Therefore, the elastic wave device 10A according to the second embodiment can increase the overall capacitance of the capacitor element 40A compared with the first embodiment.

[0060] (Third implementation)

[0061] Figure 6 This is a circuit diagram illustrating the elastic wave device according to the third embodiment. Figure 6 As shown, the elastic wave device 10B according to the third embodiment differs from the embodiments described above in the following way: it has multiple resonators.

[0062] More specifically, the elastic wave device 10B includes multiple series-arm resonators S1, S2, S3, multiple parallel-arm resonators P1, P2, and a capacitor element 40. The multiple series-arm resonators S1, S2, S3 are connected in series in the signal path between the input terminal 61 and the output terminal 62. The multiple parallel-arm resonators P1, P2 are connected in parallel between a node on the signal path connecting the input terminal 61 and the output terminal 62 and a reference potential 63. The elastic wave device 10B according to the third embodiment is known as a trapezoidal filter.

[0063] One terminal of each of the series-connected series-arm resonators S1, S2, and S3 is electrically connected to the input terminal 61, and the other terminal is electrically connected to the output terminal 62. One terminal of the parallel-arm resonator P1 is electrically connected to a node in the signal path connecting series-arm resonators S1 and S2, and the other terminal is electrically connected to a reference potential 63. One terminal of the parallel-arm resonator P2 is electrically connected to a node in the signal path connecting series-arm resonators S2 and S3, and the other terminal is electrically connected to a reference potential 63.

[0064] In this embodiment, the reference potential 63 is, for example, the ground potential. However, the reference potential 63 is not limited to the ground potential and may be any other given potential.

[0065] Capacitor element 40 is connected in parallel to series arm resonator S1. That is, capacitor element 40 is connected in parallel with series arm resonator S1 and in series between input terminal 61 and output terminal 62. More specifically, one end of capacitor element 40 is electrically connected to a node on the signal path connecting input terminal 61 and series arm resonator S1. The other end of capacitor element 40 is electrically connected to a node on the signal path connecting series arm resonators S1 and S2.

[0066] Figure 7 The graphs show the transmission characteristics of the elastic wave devices involved in Embodiment 1 and Comparative Examples 1 and 2. Figure 7 The elastic wave device involved in Embodiment 1 shown is Figure 6The so-called trapezoidal filter shown is constructed by connecting a capacitor element 40 to the series arm resonator S1. The elastic wave device involved in Comparative Example 1 is the same trapezoidal filter as that in Example 1, but differs from Example 1 in the following structure: no capacitor element 40 is provided. The elastic wave device involved in Comparative Example 2 is similar to Example 1 in that a capacitor element is connected to the series arm resonator S1, but differs from Example 1 in the following structure: the capacitor element has only one of the upper IDT electrode 41 and the lower IDT electrode 42.

[0067] Figure 7 The vertical axis of the graph shown represents the level (dB) of the S-parameter S21. Figure 7 The horizontal axis of the graph shown represents frequency (GHz).

[0068] like Figure 7 As shown, the elastic wave devices of Embodiment 1 and Comparative Examples 1 and 2 each have two attenuation poles in their transmission characteristics. The elastic wave device of Embodiment 1 has a capacitor element 40 connected to the series arm resonator S1. Therefore, compared with Comparative Example 1, which does not have a capacitor element 40, the attenuation pole on the high-frequency side indicated by arrow f1 can be shifted to the low-frequency side.

[0069] Furthermore, in the elastic wave device according to Embodiment 1, the capacitor element 40 has an upper IDT electrode 41 and a lower IDT electrode 42, thus forming a large capacitance compared to Comparative Example 2, which only has an upper IDT electrode 41 and a lower IDT electrode 42. Therefore, compared to Comparative Example 2, the elastic wave device according to Embodiment 1 can shift the attenuation electrode on the high-frequency side (indicated by arrow f1) towards the low-frequency side.

[0070] Therefore, the elastic wave device according to Example 1 shows that, compared with Comparative Examples 1 and 2, it can effectively adjust the transmission characteristics.

[0071] in addition, Figure 6 The structure of the elastic wave device 10B shown is merely an example and can be modified appropriately. For example, capacitor element 40A of the second embodiment can be used instead of capacitor element 40. Furthermore, the number and connection structure of the plurality of series arm resonators S1, S2, S3 and the plurality of parallel arm resonators P1, P2 can be appropriately changed according to the required transmission characteristics of the elastic wave device 10B.

[0072] (Fourth implementation)

[0073] Figure 8 This is a circuit diagram illustrating the elastic wave device according to the fourth embodiment. (As shown) Figure 8 As shown, the elastic wave device 10C according to the fourth embodiment differs from the third embodiment described above in the following structure: the capacitor element 40 is connected to the parallel arm resonator P1.

[0074] Capacitor element 40 is connected in parallel with parallel arm resonator P1. One terminal of capacitor element 40 is connected to the signal path between input terminal 61 and output terminal 62. More specifically, one terminal of capacitor element 40 is electrically connected to a node on the signal path connecting series arm resonators S1 and S2. The other terminal of capacitor element 40 is electrically connected to reference potential 63.

[0075] Furthermore, the structures of the multiple series-connected resonators S1, S2, S3 and the multiple parallel-connected resonators P1, P2 are the same as those in the third embodiment described above, and repeated descriptions are omitted.

[0076] Figure 9 The graphs show the transmission characteristics of the elastic wave devices involved in Embodiment 2 and Comparative Examples 1 and 3. Figure 9 The elastic wave device involved in Embodiment 2 shown is Figure 8 The so-called trapezoidal filter shown is constructed by connecting a capacitor element 40 to the parallel arm resonator P1. The elastic wave device involved in Comparative Example 3 is similar to Example 2 in that it connects a capacitor element to the parallel arm resonator P1, but differs from Example 2 in the following structure: the capacitor element has only one of the upper IDT electrode 41 and the lower IDT electrode 42.

[0077] like Figure 9 As shown, the elastic wave device according to Embodiment 2 has a capacitor element 40 connected to the parallel arm resonator P1. Therefore, compared with Comparative Example 1, which does not have a capacitor element 40, the low-frequency side of the two attenuation poles, indicated by arrow f2, can be shifted to the high-frequency side.

[0078] Furthermore, in the elastic wave device according to Embodiment 2, since the capacitor element 40 has an upper IDT electrode 41 and a lower IDT electrode 42, a large capacitance is formed compared to Comparative Example 3, which only has an upper IDT electrode 41 and a lower IDT electrode 42. Therefore, the elastic wave device according to Embodiment 2 can shift the attenuation electrode on the low-frequency side (indicated by arrow f2) towards the high-frequency side.

[0079] Therefore, the elastic wave device according to Example 2 shows that, compared with Comparative Examples 1 and 3, it can effectively adjust the transmission characteristics.

[0080] In addition, not limited to Figure 8 The structure of the elastic wave device 10C shown can, for example, replace the capacitor element 40 with the capacitor element 40A of the second embodiment. Furthermore, the structure of the fourth embodiment can be combined with that of the third embodiment. That is, the elastic wave device 10C can also have multiple capacitor elements 40, with capacitor elements 40 connected to both the series arm resonator S1 and the parallel arm resonator P1.

[0081] Furthermore, the above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit or explain the invention. The present invention can be modified / improved without departing from its spirit, and its equivalents are also included in the present invention.

[0082] Alternatively, this disclosure can also adopt the following structure.

[0083] (1) An elastic wave device, comprising:

[0084] A resonator includes a piezoelectric layer having a first main surface and a second main surface opposite to the first main surface, an upper electrode disposed on the first main surface of the piezoelectric layer, and a lower electrode disposed on the second main surface of the piezoelectric layer; and

[0085] The capacitor element includes an upper IDT (Interdigital Transducer) electrode disposed on the first main surface of the piezoelectric layer, and a lower IDT electrode disposed on the second main surface of the piezoelectric layer.

[0086] The capacitor element is connected in parallel with the resonator.

[0087] The upper IDT electrode and the lower IDT electrode of the capacitor element are electrically connected.

[0088] (2) According to the elastic wave device described in (1), wherein,

[0089] The upper IDT electrode and the lower IDT electrode each comprise a plurality of electrode fingers arranged in a given direction.

[0090] The plurality of electrode fingers of the upper IDT electrode and the plurality of electrode fingers of the lower IDT electrode are arranged opposite each other, sandwiching the piezoelectric layer.

[0091] The same potential is supplied to the electrode fingers of the upper IDT electrode and the electrode fingers of the lower IDT electrode, which are arranged opposite to each other and sandwiched between the piezoelectric layers.

[0092] (3) According to the elastic wave device described in (1), wherein,

[0093] The upper IDT electrode and the lower IDT electrode each comprise a plurality of electrode fingers arranged in a given direction.

[0094] The plurality of electrode fingers of the upper IDT electrode and the plurality of electrode fingers of the lower IDT electrode are arranged opposite each other, sandwiching the piezoelectric layer.

[0095] Different potentials are supplied to the electrode fingers of the upper IDT electrode and the electrode fingers of the lower IDT electrode, which are arranged opposite to each other and sandwiched between the piezoelectric layers.

[0096] (4) The elastic wave device described in any one of (1) to (3), wherein,

[0097] The upper IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers arranged alternately in a given direction.

[0098] The lower IDT electrode includes a plurality of third electrode fingers and a plurality of fourth electrode fingers arranged alternately in a given direction.

[0099] The plurality of first electrode fingers of the upper IDT electrode and the plurality of third electrode fingers of the lower IDT electrode are electrically connected through a first via penetrating the piezoelectric layer.

[0100] The plurality of second electrode fingers of the upper IDT electrode and the plurality of fourth electrode fingers of the lower IDT electrode are electrically connected through a second via penetrating the piezoelectric layer.

[0101] (5) According to the elastic wave device described in (4), wherein,

[0102] The plurality of first electrode fingers of the upper IDT electrode and the plurality of third electrode fingers of the lower IDT electrode are electrically connected to one of the upper electrode and the lower electrode of the resonator.

[0103] The plurality of second electrode fingers of the upper IDT electrode and the plurality of fourth electrode fingers of the lower IDT electrode are electrically connected to the other of the upper electrode and the lower electrode of the resonator.

[0104] (6) The elastic wave device described in any one of (1) to (5), wherein,

[0105] The elastic wave device has multiple resonators.

[0106] The plurality of resonators include series-arm resonators and parallel-arm resonators.

[0107] The series arm resonator is connected in series between the input terminal and the output terminal.

[0108] The parallel arm resonator is connected in parallel between the signal path and the reference potential between the input terminal and the output terminal.

[0109] The capacitor element is connected in parallel with the series arm resonator and in series between the input terminal and the output terminal.

[0110] (7) The elastic wave device described in any one of (1) to (5), wherein,

[0111] The elastic wave device has multiple resonators.

[0112] The plurality of resonators include series-arm resonators and parallel-arm resonators.

[0113] The series arm resonator is connected in series between the input terminal and the output terminal.

[0114] The parallel arm resonator is connected in parallel between the signal path and the reference potential between the input terminal and the output terminal.

[0115] The capacitor element is connected in parallel with the parallel arm resonator, and one terminal of the capacitor element is connected to the signal path between the input terminal and the output terminal, while the other terminal of the capacitor element is connected to the reference potential.

[0116] (8) The elastic wave device described in any one of (1) to (7), wherein,

[0117] The piezoelectric layer comprises single-crystal lithium niobate or lithium tantalate.

[0118] Explanation of reference numerals in the attached figures

[0119] 10, 10A, 10B, 10C Elastic Wave Devices

[0120] 11 Support base plate

[0121] 12 Insulation layer

[0122] 13 Supporting components

[0123] 14 cavity

[0124] 20 piezoelectric layers

[0125] 20a 1st main side

[0126] 20b Second Main Page

[0127] 30 resonators

[0128] 31 Upper electrode

[0129] 32 Lower electrode

[0130] Connection wiring for 33, 34, 37, and 38.

[0131] 40A and 40A capacitor components

[0132] 41 Upper IDT electrode

[0133] 42 Lower IDT electrode

[0134] 43A First Electrode Finger

[0135] 43B Third Electrode Finger

[0136] 44A Second Electrode Finger

[0137] 44B Fourth Electrode Finger

[0138] P1 and P2 parallel arm resonators

[0139] S1, S2, S3 series arm resonators

[0140] 61 Input Terminals

[0141] 62 Output Terminals

[0142] 63. Reference potential.

Claims

1. An elastic wave device, comprising: a resonator including a piezoelectric layer having a first main surface and a second main surface opposite to the first main surface, an upper electrode provided on the first main surface of the piezoelectric layer, and a lower electrode provided on the second main surface of the piezoelectric layer; and a capacitive element including an upper IDT electrode, i.e., an upper interdigital transducer electrode, provided on the first main surface of the piezoelectric layer, and a lower IDT electrode provided on the second main surface of the piezoelectric layer, the capacitive element being connected in parallel to the resonator, the upper IDT electrode and the lower IDT electrode of the capacitive element being electrically connected.

2. The elastic wave device according to claim 1, wherein the upper IDT electrode and the lower IDT electrode each include a plurality of electrode fingers arranged in a given direction, the plurality of electrode fingers of the upper IDT electrode and the plurality of electrode fingers of the lower IDT electrode are disposed in opposition to each other with the piezoelectric layer interposed therebetween, and the same potential is supplied to the electrode fingers of the upper IDT electrode and the electrode fingers of the lower IDT electrode disposed in opposition to each other with the piezoelectric layer interposed therebetween.

3. The elastic wave device according to claim 1, wherein the upper IDT electrode and the lower IDT electrode each include a plurality of electrode fingers arranged in a given direction, the plurality of electrode fingers of the upper IDT electrode and the plurality of electrode fingers of the lower IDT electrode are disposed in opposition to each other with the piezoelectric layer interposed therebetween, and different potentials are supplied to the electrode fingers of the upper IDT electrode and the electrode fingers of the lower IDT electrode disposed in opposition to each other with the piezoelectric layer interposed therebetween.

4. The elastic wave device according to any one of claims 1 to 3, wherein the upper IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers alternately arranged in a given direction, the lower IDT electrode includes a plurality of third electrode fingers and a plurality of fourth electrode fingers alternately arranged in the given direction, the plurality of first electrode fingers of the upper IDT electrode and the plurality of third electrode fingers of the lower IDT electrode are electrically connected through a first via hole that penetrates the piezoelectric layer, and the plurality of second electrode fingers of the upper IDT electrode and the plurality of fourth electrode fingers of the lower IDT electrode are electrically connected through a second via hole that penetrates the piezoelectric layer.

5. The elastic wave device according to claim 4, wherein the plurality of first electrode fingers of the upper IDT electrode and the plurality of third electrode fingers of the lower IDT electrode are electrically connected to one of the upper electrode and the lower electrode of the resonator, and the plurality of second electrode fingers of the upper IDT electrode and the plurality of fourth electrode fingers of the lower IDT electrode are electrically connected to the other of the upper electrode and the lower electrode of the resonator.

6. The elastic wave device according to any one of claims 1 to 5, wherein the elastic wave device has a plurality of the resonators, the plurality of resonators include a series arm resonator and a parallel arm resonator, and the series arm resonator and the parallel arm resonator are connected in parallel to each other. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ the series arm resonator is connected in series between an input terminal and an output terminal, the shunt arm resonator is connected in parallel between a signal path between the input terminal and the output terminal and a reference potential, the capacitor element is connected in parallel with the series arm resonator and is connected in series between the input terminal and the output terminal.

7. The elastic wave device according to any one of claims 1 to 5, wherein the elastic wave device has a plurality of the resonators, the plurality of the resonators include a series arm resonator and a shunt arm resonator, the series arm resonator is connected in series between an input terminal and an output terminal, the shunt arm resonator is connected in parallel between a signal path between the input terminal and the output terminal and a reference potential, the capacitor element is connected in parallel with the shunt arm resonator and one terminal of the capacitor element is connected to the signal path between the input terminal and the output terminal and the other terminal of the capacitor element is connected to the reference potential.

8. The elastic wave device according to any one of claims 1 to 7, wherein the piezoelectric layer includes single-crystal lithium niobate or lithium tantalate.

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