Elastic wave device

Abstract

This elastic wave device comprises: a resonator that includes a piezoelectric layer having a first main surface and a second main surface on the opposite side from 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 that is provided on the first main surface or the second main surface of the piezoelectric layer, and is electrically connected to the resonator, wherein the capacitive element has an IDT (Interdigital Transducer) electrode that includes a plurality of electrode fingers that are arranged in a predetermined direction.

Description

Elastic Wave Device

[0001] The present invention relates to an acoustic wave device.

[0002] Patent Document 1 describes an acoustic wave device in which flat upper and lower electrodes are provided on both sides of a piezoelectric layer.

[0003] U.S. Patent No. 9,602,076

[0004] In such an elastic wave device, it is necessary to suppress unwanted waves generated from the resonator. In the elastic wave device disclosed in Patent Document 1, a capacitive electrode is provided on a dielectric layer that supports a piezoelectric layer, which may make it difficult to adjust the capacitance value formed by the capacitive electrode. As a result, it may be difficult to suppress unwanted waves generated from the resonator in the elastic wave device disclosed in Patent Document 1.

[0005] An object of the present invention is to provide an acoustic wave device that can suppress unwanted waves generated from a resonator.

[0006] An elastic wave device according to one embodiment includes a piezoelectric layer having a first main surface and a second main surface opposite the first main surface, a resonator including 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 provided on the first main surface or the second main surface of the piezoelectric layer and electrically connected to the resonator, wherein the capacitive element has an IDT (Interdigital Transducer) electrode including a plurality of electrode fingers arranged in a predetermined direction.

[0007] According to the acoustic wave device of the present invention, it is possible to suppress unwanted waves generated from the resonator.

[0008] FIG. 1 is a circuit diagram illustrating an elastic wave device according to a first embodiment. FIG. 2 is a plan view illustrating the elastic wave device according to the first embodiment. FIG. 3 is a cross-sectional view taken along III-III′ in FIG. 2 . FIG. 4 is a cross-sectional view taken along IV-IV′ in FIG. 2 . FIG. 5 is a graph schematically illustrating the pass characteristics of an elastic wave device according to a comparative example. FIG. 6 is a graph schematically illustrating the pass characteristics of an elastic wave device according to an example. FIG. 7 is an explanatory diagram illustrating the relationship between the resonant frequency of an unwanted wave indicated by dotted line F1 in FIG. 5 and the resonant frequencies of a parallel arm capacitor and a series arm capacitor. FIG. 8 is a plan view schematically illustrating an enlarged IDT electrode. FIG. 9 is a circuit diagram illustrating an elastic wave device according to a second embodiment. FIG. 10 is a plan view illustrating an elastic wave device according to the second embodiment. FIG. 11 is a circuit diagram illustrating an elastic wave device according to a modification. FIG. 12 is a plan view illustrating an elastic wave device according to a modification. FIG. 13 is a circuit diagram illustrating an elastic wave device according to a third embodiment. FIG. 14 is a plan view illustrating an elastic wave device according to the third embodiment. Fig. 15 is a circuit diagram illustrating an elastic wave device according to a fourth preferred embodiment of the present invention. Fig. 16 is a plan view illustrating an elastic wave device according to the fourth preferred embodiment of the present invention. Fig. 17 is a plan view illustrating an elastic wave device according to a fifth preferred embodiment of the present invention. Fig. 18 is a circuit diagram illustrating an elastic wave device according to a sixth preferred embodiment of the present invention.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is an example, and in the second and subsequent embodiments, a description of modifications in which partial substitution or combination of configurations is possible between different embodiments, and of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0010] First Embodiment FIG. 1 is a circuit diagram illustrating an elastic wave device according to a first embodiment. As shown in FIG. 1 , an elastic wave device 10 according to the first embodiment includes a series arm resonator 51, a parallel arm resonator 52, a series arm capacitor 53, and a parallel arm capacitor 54. The resonators (series arm resonator 51 and parallel arm resonator 52) constituting elastic wave device 10 according to the first embodiment are resonators that utilize bulk waves, i.e., BAW (Bulk Acoustic Wave) elements. Furthermore, the capacitors (series arm capacitor 53 and parallel arm capacitor 54) constituting elastic wave device 10 are resonators that utilize surface acoustic waves, i.e., SAW (Surface Acoustic Wave) elements.

[0011] The series arm resonator 51 is connected in series to a signal path between an input terminal 61 and an output terminal 62. The parallel arm resonator 52 is connected in parallel between the signal path between the input terminal 61 and the output terminal 62 and a reference potential 63. The series arm capacitive element 53 is connected in series to the signal path between the input terminal 61 and the output terminal 62 and in parallel to the series arm resonator 51. The parallel arm capacitive element 54 is connected in parallel between the signal path between the input terminal 61 and the output terminal 62 and the reference potential 63 and in parallel to the parallel arm resonator 52.

[0012] In this embodiment, the reference potential 63 is, for example, a ground potential, but the reference potential 63 is not limited to the ground potential and may be another predetermined potential.

[0013] The series arm resonator 51, the parallel arm resonator 52, the series arm capacitive element 53, and the parallel arm capacitive element 54 share a common node N1. More specifically, one terminal of the series arm resonator 51 is connected to an input terminal 61, and the other terminal of the series arm resonator 51 is connected to the node N1. One terminal of the parallel arm resonator 52 is connected to the node N1, and the other terminal of the parallel arm resonator 52 is connected to a reference potential 63.

[0014] One terminal of the series arm capacitive element 53 is connected to the input terminal 61 and one terminal of the series arm resonator 51, and the other terminal of the series arm capacitive element 53 is connected to the node N1 and the other terminal of the series arm resonator 51. One terminal of the parallel arm capacitive element 54 is connected to the node N1 and one terminal of the parallel arm resonator 52, and the other terminal of the parallel arm capacitive element 54 is connected to a reference potential 63. The node N1 is connected to the output terminal 62.

[0015] In this embodiment, the parallel arm capacitor 54 is connected to the series arm resonator 51, so that the parallel arm capacitor 54 can suppress unwanted waves generated from the series arm resonator 51. Furthermore, the series arm capacitor 53 is connected to the parallel arm resonator 52, so that the series arm capacitor 53 can suppress unwanted waves generated from the parallel arm resonator 52. Details of the pass characteristics of each resonator and the method of suppressing unwanted waves will be described later with reference to FIG. 5 and subsequent figures.

[0016] Fig. 2 is a plan view showing the elastic wave device according to the first preferred embodiment. Fig. 3 is a cross-sectional view taken along line III-III' in Fig. 2. Fig. 4 is a cross-sectional view taken along line IV-IV' in Fig. 2. Specifically, Fig. 3 is a cross-sectional view schematically showing a series arm resonator 51 and a parallel arm capacitor 54. Fig. 4 is a cross-sectional view schematically showing a parallel arm resonator 52 and a series arm capacitor 53.

[0017] 2 to 4 , the elastic wave device 10 includes a support member 13, a piezoelectric layer 20, an upper electrode 31, a lower electrode 32, and IDT (Interdigital Transducer) electrodes 40 and 40A. As shown in Fig. 3 , the lower electrode 32 (first main electrode portion 32a), the piezoelectric layer 20, and the upper electrode 31 (first main electrode portion 31a) are stacked in this order on the support member 13 to form a series arm resonator 51. Similarly, as shown in Fig. 4 , the lower electrode 32 (second main electrode portion 32b), the piezoelectric layer 20, and the upper electrode 31 (second main electrode portion 31b) are stacked in this order on the support member 13 to form a parallel arm resonator 52.

[0018] In the following description, the thickness direction of the piezoelectric layer 20 is referred to as the Z direction, the direction perpendicular to the Z direction is referred to as the X direction, and the direction perpendicular to the Z direction and the X direction is referred to as the Y direction. The X direction and the Y direction are each parallel to the surface (first main surface 20a) of the piezoelectric layer 20. In the following description, a plan view refers to the positional relationship when viewed from a direction perpendicular to the first main surface 20a of the piezoelectric layer 20 (Z direction).

[0019] The support member 13 is disposed 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 is made of silicon (Si), quartz crystal, 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. Note that the support member 13 may be configured without the insulating layer 12, with the piezoelectric layer 20 disposed on the support substrate 11. An adhesion layer of Ti, NiCr, or the like may be disposed between the lower electrode 32 and the insulating layer 12.

[0020] Cavities 14 and 15 (hollow portions) are formed on the surface of the support member 13 (insulating layer 12) facing the second main surface 20b of the piezoelectric layer 20. The cavity 14 is provided so as to overlap, in plan view, with the excitation region of the series arm resonator 51 configured by overlapping the piezoelectric layer 20, the upper electrode 31, and the lower electrode 32. This allows the bulk wave to be reflected by the cavity 14. The cavity 15 is also provided so as to overlap, in plan view, with the excitation region of the parallel arm resonator 52 configured by overlapping the piezoelectric layer 20, the upper electrode 31, and the lower electrode 32. This allows the bulk wave to be reflected by the cavity 15.

[0021] The piezoelectric layer 20 is in the form of 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 made of lithium niobate (LiNbO ３ ) or lithium tantalate (LiTaO ３ The thickness of the piezoelectric layer 20 is not particularly limited, but is preferably 1 μm or less.

[0022] The upper electrode 31 is provided on the first main surface 20a of the piezoelectric layer 20. As shown in FIG. 2, the upper electrode 31 has a first main electrode portion 31a, a second main electrode portion 31b, and connection portions 31c, 31d, and 31e. The first main electrode portion 31a is provided in the excitation region of the series arm resonator 51 and is formed in a substantially circular shape. The second main electrode portion 31b is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. The connection portions 31c and 31d connect the first main electrode portion 31a and the second main electrode portion 31b. The connection portion 31c is connected to the first main electrode portion 31a and extends in the X direction. The connection portion 31d extends from the connection portion 31c in the Y direction and is connected to the second main electrode portion 31b. The connection portion 31e extends from the connection portion 31c in the Y direction and is electrically connected to the IDT electrode 40A.

[0023] The lower electrode 32 is provided on the second main surface 20b of the piezoelectric layer 20, in a region where at least a portion of the lower electrode 32 overlaps with the upper electrode 31. As shown in Fig. 2, the lower electrode 32 has a first main electrode portion 32a, a second main electrode portion 32b, and connection portions 32c and 32d. The first main electrode portion 32a is provided in the excitation region of the series arm resonator 51 and is formed in a substantially circular shape. That is, the first main electrode portion 32a of the lower electrode 32 is provided in a region where the first main electrode portion 31a of the upper electrode 31 overlaps with the first main electrode portion 31a of the upper electrode 31, with the piezoelectric layer 20 sandwiched between them. The connection portion 32c is connected to the first main electrode portion 32a and extends in the X direction on the side opposite to the connection portion 31c of the upper electrode 31.

[0024] The second main electrode portion 32b of the lower electrode 32 is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. That is, the second main electrode portion 32b of the lower electrode 32 is provided in a region overlapping the second main electrode portion 31b of the upper electrode 31, with the piezoelectric layer 20 sandwiched therebetween. The connection portion 32d is connected to the second main electrode portion 32b and extends in the Y direction on the side opposite to the connection portion 31d of the upper electrode 31. The extension direction of the series arm resonator 51 (the extension direction of the connection portions 31c and 32c) is perpendicular to the extension direction of the parallel arm resonator 52 (the extension direction of the connection portions 31d and 32d).

[0025] The upper electrode 31 and the lower electrode 32 are formed of a metal such as aluminum (Al), platinum (Pt), copper (Cu), tungsten (W), or molybdenum (Mo), or an alloy containing at least one of these materials. The upper electrode 31 and the lower electrode 32 may be a laminated film.

[0026] The series arm resonator 51 and the parallel arm resonator 52 have a so-called membrane structure in which cavities 14, 15 (hollow portions) are provided on the second main surface 20b side of the piezoelectric layer 20. As shown in FIG. 3 , in the region overlapping with the cavity 14, the piezoelectric layer 20 is disposed between the first main electrode portion 31a of the upper electrode 31 and the first main electrode portion 32a of the lower electrode 32 in the Z direction. This allows bulk waves to propagate between the first main electrode portion 31a of the upper electrode 31 and the first main electrode portion 32a of the lower electrode 32. As shown in FIG. 4 , in the region overlapping with the cavity 15, the piezoelectric layer 20 is disposed between the second main electrode portion 31b of the upper electrode 31 and the second main electrode portion 32b of the lower electrode 32 in the Z direction. This allows bulk waves to propagate between the second main electrode portion 31b of the upper electrode 31 and the second main electrode portion 32b of the lower electrode 32.

[0027] As shown in FIG. 2 , the series arm capacitor 53 includes an IDT electrode 40A. The parallel arm capacitor 54 includes an IDT electrode 40. The IDT electrode 40 of the parallel arm capacitor 54 includes electrode fingers 41 and 42 and busbar electrodes 43 and 44. The electrode fingers 41 extend in the Y direction, and one end of the electrode fingers 41 is connected to the busbar electrode 43. The electrode fingers 42 extend in the Y direction, and the other end of the electrode fingers 41 is connected to the busbar electrode 44. The electrode fingers 41 and the electrode fingers 42 are alternately arranged in the X direction with a gap therebetween. The busbar electrodes 43 and 44 each extend in the X direction and are spaced apart in the Y direction. The electrode fingers 41 and 42 are arranged between the busbar electrode 43 and the busbar electrode 44.

[0028] The bus bar electrode 43 of the IDT electrode 40 is connected to the connection portion 31c of the upper electrode 31 through a connection wiring 45. A connection wiring 46 is connected to the bus bar electrode 44 of the IDT electrode 40. As shown in Fig. 3, the IDT electrode 40 and the connection wirings 45 and 46 are provided on the first main surface 20a of the piezoelectric layer 20 in the same layer as the upper electrode 31.

[0029] As shown in FIG. 2 , the IDT electrode 40A of the series arm capacitor 53 has electrode fingers 41A and 42A and busbar electrodes 43A and 44A. The IDT electrode 40A has a configuration similar to that of the IDT electrode 40 described above, and a repeated description will be omitted. The IDT electrode 40A is arranged rotated 90° with respect to the IDT electrode 40. That is, the extension direction of the electrode fingers 41A and 42A of the IDT electrode 40A of the series arm capacitor 53 is perpendicular to the extension direction of the electrode fingers 41 and 42 of the IDT electrode 40 of the parallel arm capacitor 54. The multiple electrode fingers 41A and 42A extend in the X direction and are alternately arranged with intervals in the Y direction. The busbar electrodes 43A and 44A also extend in the Y direction and are spaced apart in the X direction.

[0030] The extending direction of the electrode fingers 41A and 42A of the IDT electrode 40A of the series arm capacitive element 53 is perpendicular to the extending direction of the parallel arm resonator 52 (the extending direction of the connecting portion 31d and the connecting portion 32d). Moreover, the extending direction of the electrode fingers 41 and 42 of the IDT electrode 40 of the parallel arm capacitive element 54 is perpendicular to the extending direction of the series arm resonator 51 (the extending direction of the connecting portion 31c and the connecting portion 32c).

[0031] The bus bar electrode 43A of the IDT electrode 40A is connected to the connection portion 32c of the lower electrode 32 through a connection wiring 45A. A connection wiring 46A is connected to the bus bar electrode 44A of the IDT electrode 40A. The connection wiring 46A is connected to the connection portion 31e of the upper electrode 31 through a via 47. As shown in FIG. 4 , the IDT electrode 40A and the connection wirings 45A and 46A are provided on the second main surface 20b of the piezoelectric layer 20 in the same layer as the lower electrode 32.

[0032] With the above configuration, the series arm resonators 51, parallel arm resonators 52, series arm capacitors 53, and parallel arm capacitors 54 are formed on the common piezoelectric layer 20. As shown in Fig. 2, the connection portion 31c of the upper electrode 31 corresponds to the node N1 in Fig. 1. That is, the IDT electrode 40 is provided on the same layer as the first main electrode portion 31a (series arm resonators 51) of the upper electrode 31, which is connected to the common node N1. The IDT electrode 40A is provided on a different layer from the second main electrode portion 31b (parallel arm resonators 52) of the upper electrode 31, which is connected to the common node N1.

[0033] 2 is electrically connected to an input terminal 61 through a lead-out wiring (not shown). The connection portion 31c of the upper electrode 31 is electrically connected to an output terminal 62 through a lead-out wiring (not shown). The connection portion 32d of the lower electrode 32 is electrically connected to a reference potential 63 through a lead-out wiring (not shown). The connection wiring 46 connected to the IDT electrode 40 is electrically connected to the reference potential 63 through a lead-out wiring (not shown).

[0034] Next, a configuration for suppressing unwanted waves generated from series arm resonator 51 and parallel arm resonator 52 in elastic wave device 10 will be described with reference to FIGS. 5 to 8 . FIG. 5 is a graph schematically showing the passband characteristics of an elastic wave device according to a comparative example. FIG. 6 is a graph schematically showing the passband characteristics of an elastic wave device according to an example. FIG. 7 is a diagram illustrating the relationship between the resonant frequency of unwanted waves indicated by dotted line F1 in FIG. 5 and the resonant frequencies of the parallel arm capacitors and the series arm capacitors. FIG. 8 is a plan view schematically illustrating an enlarged view of an IDT electrode.

[0035] The elastic wave device according to the comparative example shown in Fig. 5 has a configuration in which the series arm resonator 51 and the parallel arm resonator 52 are provided, but the series arm capacitor 53 and the parallel arm capacitor 54 are not provided, in elastic wave device 10 shown in Fig. 1 to Fig. 4. The elastic wave device according to the example shown in Fig. 6 has the series arm resonator 51, the parallel arm resonator 52, the series arm capacitor 53, and the parallel arm capacitor 54 shown in Fig. 1 to Fig. 4.

[0036] The vertical axis of graph 1 shown in Fig. 5 and graph 2 shown in Fig. 6 represents the pass characteristic (level (dB) of S parameter S21), and the horizontal axis of graph 1 shown in Fig. 5 and graph 2 shown in Fig. 6 represents frequency (GHz).

[0037] 5 , in the elastic wave device of the comparative example, the resonant frequencies of series arm resonator 51 and parallel arm resonator 52 are in the range of 3.3 GHz to 4.2 GHz. The elastic wave device of the comparative example also generates unwanted waves in the frequency range of 1.8 GHz to 2.5 GHz, as indicated by dotted line F1.

[0038] 6 , in the elastic wave device according to the example, similar to the comparative example, the resonant frequencies of series arm resonator 51 and parallel arm resonator 52 are in the range of 3.3 GHz to 4.2 GHz. In the elastic wave device according to the example, series arm capacitive element 53 and parallel arm capacitive element 54 are provided, and therefore, it is shown that the generation of unwanted waves is suppressed in the frequency range of 1.8 GHz to 2.5 GHz, as indicated by dotted line F2.

[0039] More specifically, in the elastic wave device according to the embodiment, the material of the piezoelectric layer 20 is LiNbO 3 , which has a sound velocity of about 4000 m / s. ３ In addition, for the series arm capacitor 53 and the parallel arm capacitor 54, the arrangement pitch p (see FIG. 8) of the electrode fingers 41, 41A of the IDT electrodes 40, 40A was adjusted in the range of 1.6 μm to 2.2 μm.

[0040] The upper diagram in Fig. 7 shows waveforms that schematically illustrate enlarged portions of the spurious waves generated from the series arm resonator 51 and the parallel arm resonator 52. The lower diagram in Fig. 7 shows waveforms that schematically illustrate enlarged portions of the passband characteristics of the IDT electrodes 40 and 40A that constitute the series arm capacitive element 53 and the parallel arm capacitive element 54. As shown in Fig. 7, the resonant frequency f11 of the IDT electrode 40A of the series arm capacitive element 53 is approximately equal to the resonant frequency f1 of the parallel arm resonator 52. The passband characteristics of the IDT electrode 40A of the series arm capacitive element 53 have a waveform that is inverted relative to the parallel arm resonator 52. As a result, in the elastic wave device 10 according to the embodiment, the series arm capacitive element 53 is connected to the parallel arm resonator 52, and therefore the spurious waves generated from the parallel arm resonator 52 are canceled (offset).

[0041] Similarly, the resonant frequency f12 of the IDT electrode 40 of the parallel arm capacitive element 54 is approximately equal to the resonant frequency f2 of the series arm resonator 51. The pass characteristics of the IDT electrode 40 of the parallel arm capacitive element 54 have a waveform that is inverted with respect to the series arm resonator 51. As a result, in the elastic wave device 10 according to the embodiment, the parallel arm capacitive element 54 is connected to the series arm resonator 51, and therefore, unwanted waves generated from the series arm resonator 51 are canceled (offset).

[0042] As shown in Fig. 8 , the resonant frequency f12 of the IDT electrode 40 of the parallel arm capacitance element 54 can be adjusted by changing the arrangement pitch p of the electrode fingers 41. The arrangement pitch p of the electrode fingers 41 is the distance between the sides of two electrode fingers 41 adjacent in the X direction with one electrode finger 42 sandwiched between them in the X direction (the right sides of the electrode fingers 41 in Fig. 8 ). Note that although Fig. 8 describes the arrangement pitch p of the electrode fingers 41, the arrangement pitch p of the electrode fingers 42 is also equal to the arrangement pitch p of the electrode fingers 41. The arrangement pitch p of the electrode fingers 41A and 42A of the IDT electrode 40A is also defined in the same way as the arrangement pitch p shown in Fig. 8 .

[0043] As described above, the elastic wave device of this preferred embodiment includes resonators (series arm resonators 51 and parallel arm resonators 52) each including a piezoelectric layer 20, an upper electrode 31 provided on the first main surface 20a of the piezoelectric layer 20, and a lower electrode provided on the second main surface 20b of the piezoelectric layer 20, and capacitive elements (series arm capacitive elements 53 and parallel arm capacitive elements 54) provided on the first main surface 20a or the second main surface 20b of the piezoelectric layer 20 and electrically connected to the resonators. The capacitive elements include IDT electrodes 40 and 40A each including a plurality of electrode fingers 41, 42, 41A, and 42A arranged in a predetermined direction.

[0044] As a result, the parallel arm capacitive element 54 is connected to the series arm resonator 51, and the series arm capacitive element 53 is connected to the parallel arm resonator 52. Therefore, unwanted waves generated from the resonators (the series arm resonators 51 and the parallel arm resonators 52) are canceled (offset) by the capacitive elements (the series arm capacitive element 53 and the parallel arm capacitive element 54).

[0045] Alternatively, the elastic wave device 10 of this preferred embodiment can adjust the pass characteristics of the resonators (series arm resonator 51 and parallel arm resonator 52) that are BAW elements by providing capacitive elements (series arm capacitive element 53 and parallel arm capacitive element 54) that are SAW elements. In this case, the propagation modes of the SAW elements and the BAW elements are different. Therefore, if separate measures were taken to suppress the unwanted waves generated by the capacitive elements and the resonators, the configuration of the elastic wave device 10 would become complicated. In this preferred embodiment, the resonant frequency of the capacitive elements is approximately equal to the resonant frequency of the resonators, thereby suppressing the unwanted waves from the capacitive elements and the resonators without requiring separate measures to suppress the unwanted waves. Therefore, the elastic wave device 10 of this preferred embodiment can adjust the pass characteristics of the BAW resonators by providing capacitive elements, while suppressing the unwanted waves from the capacitive elements and the resonators.

[0046] 2 to 4 are merely examples and may be modified as appropriate. The various waveforms shown in FIG. 7 are also shown schematically to facilitate understanding.

[0047] Second Embodiment Fig. 9 is a circuit diagram illustrating an elastic wave device according to a second embodiment. Fig. 10 is a plan view illustrating an elastic wave device according to the second embodiment. As shown in Figs. 9 and 10 , an elastic wave device 10A according to the second embodiment differs from the first embodiment in that it does not include parallel arm resonators 52 and series arm capacitors 53.

[0048] 9 , an elastic wave device 10A according to the second preferred embodiment includes a series arm resonator 51 and a parallel arm capacitor 54. The series arm resonator 51 is connected in series to a signal path between an input terminal 61 and an output terminal 62. The parallel arm capacitor 54 is connected in parallel between the signal path between the input terminal 61 and the output terminal 62 and a reference potential 63.

[0049] The series arm resonator 51 and the parallel arm capacitive element 54 share a common node N2. More specifically, one terminal of the series arm resonator 51 is connected to an input terminal 61, and the other terminal of the series arm resonator 51 is connected to the node N2. One terminal of the parallel arm capacitive element 54 is connected to the node N2, and the other terminal of the parallel arm capacitive element 54 is connected to a reference potential 63. The node N2 is connected to an output terminal 62.

[0050] 10 , the elastic wave device 10A includes an upper electrode 31A, a lower electrode 32A, and an IDT electrode 40. The upper electrode 31A includes a main electrode portion 31Aa and a connecting portion 31Ac. The main electrode portion 31Aa of the upper electrode 31A is provided in the excitation region of the series arm resonator 51 and has a substantially circular shape. The connecting portion 31Ac is connected to the main electrode portion 31Aa and extends in the X direction.

[0051] The lower electrode 32A has a main electrode portion 32Aa and a connection portion 32Ab connected to the main electrode portion 32Aa. The main electrode portion 32Aa of the lower electrode 32A is provided in the excitation region of the series arm resonator 51 and is formed in a substantially circular shape. That is, the main electrode portion 32Aa of the lower electrode 32A is provided in a region overlapping with the main electrode portion 31Aa of the upper electrode 31A, with the piezoelectric layer 20 sandwiched therebetween. The connection portion 32Ab is connected to the main electrode portion 32Aa and extends in the X direction on the opposite side to the connection portion 31Ac of the upper electrode 31A.

[0052] The IDT electrode 40 constituting the parallel arm capacitance element 54 is the same as that in the first embodiment described above, and a repeated description will be omitted.

[0053] With the above-described configuration, the series arm resonator 51 and the parallel arm capacitor 54 are formed on the common piezoelectric layer 20. The cross-sectional structures of the series arm resonator 51 and the parallel arm capacitor 54 of this embodiment are the same as those in FIG. 3 , and therefore repeated description will be omitted. As shown in FIG. 10 , the connection portion 31Ac of the upper electrode 31A corresponds to the node N2 in FIG. 9 . The connection portion 32Ab of the lower electrode 32A is electrically connected to the input terminal 61 through a wiring not shown. The connection portion 31Ac of the upper electrode 31A is electrically connected to the output terminal 62 through a wiring not shown. The connection wiring 46 connected to the IDT electrode 40 is electrically connected to the reference potential 63 through a wiring not shown.

[0054] In the elastic wave device 10A according to the second preferred embodiment, the spurious waves generated from the series arm resonator 51 are canceled (offset) by the parallel arm capacitive element 54, similar to the example shown in the right diagram of FIG.

[0055] 11 and 12 , elastic wave device 10B according to the modification is different from the first embodiment in that it does not include series arm resonator 51 and parallel arm capacitor 54.

[0056] 11 , an elastic wave device 10B according to a modified example includes a parallel arm resonator 52 and a series arm capacitive element 53. The parallel arm resonator 52 is connected in parallel between a signal path between an input terminal 61 and an output terminal 62 and a reference potential 63. The series arm capacitive element 53 is connected in series to the signal path between the input terminal 61 and the output terminal 62.

[0057] The parallel arm resonator 52 and the series arm capacitive element 53 have a common node N3. More specifically, one terminal of the parallel arm resonator 52 is connected to the node N3, and the other terminal of the parallel arm resonator 52 is connected to a reference potential 63. One terminal of the series arm capacitive element 53 is connected to an input terminal 61, and the other terminal of the series arm capacitive element 53 is connected to the node N3. The node N3 is connected to an output terminal 62.

[0058] 12 , the elastic wave device 10B includes an upper electrode 31B, a lower electrode 32B, and an IDT electrode 40A. The upper electrode 31B includes a main electrode portion 31Ba and connection portions 31Bb, 31Bc, and 31Bd. The main electrode portion 31Ba of the upper electrode 31B is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. The connection portion 31Bc is connected to the main electrode portion 31Ba and extends in the Y direction. The connection portion 31Bb is connected to the connection portion 31Bc and extends in the X direction. The connection portion 31Bd is connected to the connection portion 31Bb, is located on the opposite side of the connection portion 31Bc, and extends in the Y direction.

[0059] The lower electrode 32B has a main electrode portion 32Ba, a connection portion 32Bb connected to the main electrode portion 32Ba, and a connection wiring 32Bc. The main electrode portion 32Ba of the lower electrode 32B is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. That is, the main electrode portion 32Ba of the lower electrode 32B is provided in a region overlapping with the main electrode portion 31Ba of the upper electrode 31B, with the piezoelectric layer 20 sandwiched therebetween. The connection portion 32Bb is connected to the main electrode portion 32Ba and extends in the Y direction on the opposite side to the connection portion 31Bc of the upper electrode 31B.

[0060] The connection wiring 32Bc is provided in the same layer as, but separated from, the main electrode portion 32Ba and the connection portion 32Bb of the lower electrode 32B. The connection wiring 32Bc is disposed adjacent to, and spaced apart from, the connection portion 31Bb of the upper electrode 31B in the X direction.

[0061] The IDT electrode 40A constituting the series arm capacitive element 53 is the same as that in the first embodiment, and therefore a repeated description will be omitted. The bus bar electrode 43A of the IDT electrode 40A is connected to the connection wiring 32Bc through the connection wiring 45A. The bus bar electrode 44A of the IDT electrode 40A is connected to the connection portion 31Bd through the connection wiring 46A and the via 47.

[0062] With the above-described configuration, the parallel arm resonator 52 and the series arm capacitor 53 are formed on the common piezoelectric layer 20. The cross-sectional structures of the parallel arm resonator 52 and the series arm capacitor 53 are the same as those in FIG. 4 , and therefore repeated description will be omitted. As shown in FIG. 12 , the connection portion 31Bb of the upper electrode 31B corresponds to the node N3 in FIG. 11 . The connection wiring 32Bc is electrically connected to the input terminal 61 through a wiring not shown. The connection portion 31Bb of the upper electrode 31B is electrically connected to the output terminal 62 through a wiring not shown. The connection portion 32Bb of the lower electrode 32B is electrically connected to the reference potential 63 through a wiring not shown.

[0063] In the elastic wave device 10B according to this modification, the spurious waves generated from the parallel arm resonator 52 are canceled (offset) by the series arm capacitive element 53, similar to the example shown in the left diagram of FIG.

[0064] Third Preferred Embodiment Fig. 13 is a circuit diagram illustrating an elastic wave device according to a third preferred embodiment. Fig. 14 is a plan view illustrating an elastic wave device according to the third preferred embodiment. As shown in Figs. 13 and 14 , an elastic wave device 10C according to the third preferred embodiment has a different configuration from the first preferred embodiment described above in that it includes a series arm resonator 55.

[0065] 13 , one terminal of the series arm resonator 55 is connected to an input terminal 61, and the other terminal of the series arm resonator 55 is connected to one terminal of the series arm resonator 51. The series arm resonators 55 and 51 are connected in series to a signal path between the input terminal 61 and the output terminal 62.

[0066] One terminal of the series arm capacitive element 53 is connected to the input terminal 61 and one terminal of the series arm resonator 55, and the other terminal of the series arm capacitive element 53 is connected to the node N4 and the other terminal of the series arm resonator 51. That is, the series arm capacitive element 53 is connected in parallel with the series arm resonators 55 and 51 connected in series. The series arm resonator 51, the parallel arm resonator 52, the series arm capacitive element 53, and the parallel arm capacitive element 54 are directly connected to a common node N4. The series arm resonator 55 is connected to the common node N4 via the series arm resonator 51.

[0067] 14 , an elastic wave device 10C according to the third embodiment includes an upper electrode 31C, a lower electrode 32C, and IDT electrodes 40 and 40A. The upper electrode 31C includes a first major electrode portion 31Ca, a second major electrode portion 31Cb, a third major electrode portion 31Cc, and connection portions 31Cd, 31Ce, and 31Cf. The lower electrode 32C includes a first major electrode portion 32Ca, a second major electrode portion 32Cb, a third major electrode portion 32Cc, and connection portions 32Cd and 32Ce.

[0068] The first main electrode portion 31Ca of the upper electrode 31C is provided in the excitation region of the series arm resonator 51 and is formed in a substantially circular shape. The second main electrode portion 31Cb of the upper electrode 31C is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. The third main electrode portion 31Cc of the upper electrode 31C is provided in the excitation region of the series arm resonator 55 and is formed in a substantially circular shape. The connection portions 31Cd and 31Ce connect the first main electrode portion 31Ca and the second main electrode portion 31Cb. The connection portion 31Cf is connected to the third main electrode portion 31Cc and extends in the X direction on the side opposite to the connection portion 32Cd of the lower electrode 32C.

[0069] The first main electrode portion 32Ca of the lower electrode 32C is provided in the excitation region of the series arm resonator 51 and is formed in a substantially circular shape. That is, the first main electrode portion 32Ca of the lower electrode 32C is provided in a region overlapping with the first main electrode portion 31Ca of the upper electrode 31C, with the piezoelectric layer 20 sandwiched therebetween. The second main electrode portion 32Cb of the lower electrode 32C is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. That is, the second main electrode portion 32Cb of the lower electrode 32C is provided in a region overlapping with the second main electrode portion 31Cb of the upper electrode 31C, with the piezoelectric layer 20 sandwiched therebetween.

[0070] The third main electrode portion 32Cc of the lower electrode 32C is provided in the excitation region of the series arm resonator 55 and is formed in a substantially circular shape. That is, the third main electrode portion 32Cc of the lower electrode 32C is provided in a region overlapping with the third main electrode portion 31Cc of the upper electrode 31C, with the piezoelectric layer 20 sandwiched therebetween. The connection portion 32Cd extends in the X direction and connects the first main electrode portion 32Ca and the third main electrode portion 32Cc.

[0071] The IDT electrode 40 constituting the parallel arm capacitance element 54 is the same as that in the first embodiment, and a repeated description will be omitted.

[0072] The IDT electrode 40A constituting the series arm capacitive element 53 is provided on the first main surface 20a of the piezoelectric layer 20 in the same layer as the upper electrode 31C. That is, the busbar electrode 43A of the IDT electrode 40A is connected to the connection portion 31Cf of the upper electrode 31C through a connection wiring 45A. The busbar electrode 44A of the IDT electrode 40A is connected to the connection portion 31Cd of the upper electrode 31C through a connection wiring 46A.

[0073] 14, the connection portion 31Cd of the upper electrode 31C corresponds to the node N4 in FIG. 13. The connection portion 31Cf of the upper electrode 31C is electrically connected to the input terminal 61 through a wiring not shown. The connection portion 31Cd of the upper electrode 31C is electrically connected to the output terminal 62 through a wiring not shown. The connection portion 32Ce of the lower electrode 32C and the connection wiring 46 connected to the IDT electrode 40 are electrically connected to the reference potential 63 through a wiring not shown.

[0074] In the elastic wave device 10C according to the third embodiment, the IDT electrode 40A is provided on the same layer as the upper electrode 31C. Therefore, compared to the first embodiment, a signal path connecting the first principal surface 20a and the second principal surface 20b of the piezoelectric layer 20 through the via 47 between the IDT electrode 40A and the node N4 can be omitted. That is, in this embodiment, the connection wiring 46A connected to the IDT electrode 40A is directly connected to the node N4 (the connection portion 31Cd of the upper electrode 31C) on the same layer. This shortens the wiring length between the node N4 and the IDT electrode 40A, thereby suppressing the parasitic inductance of the IDT electrode 40A. As a result, the deviation in the resonant frequency of the series arm capacitive element 53 (the IDT electrode 40A) is reduced, effectively suppressing unwanted waves generated by the parallel arm resonator 52.

[0075] 15 and 16 , an elastic wave device 10D according to the fourth embodiment is different from the first embodiment in that it has a parallel arm resonator 56 and a series arm resonator 57.

[0076] One terminal of the parallel arm resonator 56 is connected to a node N5 between the series arm resonators 51 and 57. The other terminal of the parallel arm resonator 56 is connected to the parallel arm capacitive element 54. One terminal of the parallel arm capacitive element 54 is connected to the parallel arm resonator 56, and the other terminal of the parallel arm capacitive element 54 is connected to a reference potential 63.

[0077] One terminal of the series arm resonator 57 is connected to a node N5, and the other terminal of the series arm resonator 57 is connected to an output terminal 62. One terminal of the parallel arm resonator 52 is connected to a signal path between the series arm resonator 57 and the output terminal 62, and the other terminal of the parallel arm resonator 52 is connected to a reference potential 63.

[0078] As described above, in the elastic wave device 10D according to the fourth preferred embodiment, the series arm resonator 51 and the parallel arm capacitor 54 are connected via another element (the parallel arm resonator 56). Furthermore, the parallel arm resonator 52 and the series arm capacitor 53 are connected via another element (the series arm resonator 57). In this manner, even if the series arm resonator 51 and the parallel arm capacitor 54 are not directly connected to the node N5, the parallel arm capacitor 54 can suppress unwanted waves generated from the series arm resonator 51. Furthermore, even if the parallel arm resonator 52 and the series arm capacitor 53 are not directly connected to the node N5, the series arm capacitor 53 can suppress unwanted waves generated from the parallel arm resonator 52.

[0079] 16 , an elastic wave device 10D according to the fourth embodiment includes an upper electrode 31D, a lower electrode 32D, and IDT electrodes 40 and 40A. The upper electrode 31D includes a first main electrode portion 31Da, a second main electrode portion 31Db, a third main electrode portion 31Dc, a fourth main electrode portion 31Dd, and connection portions 31De and 31Df.

[0080] The first main electrode portion 31Da of the upper electrode 31D is provided in the excitation region of the series arm resonator 51 and is formed in a substantially circular shape. The second main electrode portion 31Db is provided in the excitation region of the series arm resonator 57 and is formed in a substantially circular shape. The third main electrode portion 31Dc is provided in the excitation region of the parallel arm resonator 56 and is formed in a substantially circular shape. The fourth main electrode portion 31Dd is provided in the excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. The connection portion 31De connects the first main electrode portion 31Da, the second main electrode portion 31Db, and the third main electrode portion 31Dc. The connection portion 31Df is connected to the fourth main electrode portion 31Dd and extends in the Y direction.

[0081] The lower electrode 32D has a first major electrode portion 32Da, a second major electrode portion 32Db, a third major electrode portion 32Dc, a fourth major electrode portion 32Dd, and connection portions 32De and 32Df.

[0082] The first main electrode portion 32Da of the lower electrode 32D is formed in a substantially circular shape and is provided in the excitation region of the series arm resonator 51. That is, the first main electrode portion 32Da of the lower electrode 32D is provided in a region overlapping the first main electrode portion 31Da of the upper electrode 31D with the piezoelectric layer 20 interposed therebetween. The second main electrode portion 32Db of the lower electrode 32D is formed in a substantially circular shape and is provided in the excitation region of the series arm resonator 57. That is, the second main electrode portion 32Db of the lower electrode 32D is provided in a region overlapping the second main electrode portion 31Db of the upper electrode 31D with the piezoelectric layer 20 interposed therebetween.

[0083] The third main electrode portion 32Dc of the lower electrode 32D is provided in an excitation region of the parallel arm resonator 56 and is formed in a substantially circular shape. That is, the third main electrode portion 32Dc of the lower electrode 32D is provided in a region overlapping with the third main electrode portion 31Dc of the upper electrode 31D, with the piezoelectric layer 20 sandwiched therebetween. The fourth main electrode portion 32Dd is provided in an excitation region of the parallel arm resonator 52 and is formed in a substantially circular shape. That is, the fourth main electrode portion 32Dd of the lower electrode 32D is provided in a region overlapping with the fourth main electrode portion 31Dd of the upper electrode 31D, with the piezoelectric layer 20 sandwiched therebetween.

[0084] The connection portion 32De is connected to the first major electrode portion 32Da and extends in the X direction on the opposite side of the upper electrode 31D from the connection portion 31De. The connection portion 32Df connects the second major electrode portion 32Db and the fourth major electrode portion 32Dd.

[0085] The bus bar electrodes 43 of the IDT electrode 40 are connected to the third main electrode portion 32Dc (parallel arm resonator 56) of the lower electrode 32D through connection wiring 45. In this embodiment, the IDT electrode 40 is provided in the same layer as the lower electrode 32D.

[0086] The bus bar electrode 43A of the IDT electrode 40A is connected to the connection portion 32De of the lower electrode 32D through a connection wiring 45A. The bus bar electrode 44A of the IDT electrode 40A is connected to the connection portion 31De of the upper electrode 31D through a connection wiring 46A and a via 47. In this embodiment, the IDT electrode 40A is provided in the same layer as the lower electrode 32D.

[0087] 16, the connection portion 31De of the upper electrode 31D corresponds to the node N5 in FIG. 15. The connection portion 32De of the lower electrode 32D is electrically connected to the input terminal 61 through a lead wiring (not shown). The connection portion 32Df of the lower electrode 32D is electrically connected to the output terminal 62 through a lead wiring (not shown). The connection portion 31Df of the upper electrode 31D and the connection wiring 46 connected to the IDT electrode 40 are electrically connected to a reference potential 63 through a lead wiring (not shown).

[0088] As described above, the elastic wave device 10D according to the fourth preferred embodiment is provided with the parallel arm resonator 56 and the series arm resonator 57, thereby improving the degree of freedom in design compared to the first preferred embodiment described above.

[0089] 15 and 16 are merely examples and can be modified as appropriate. For example, in FIGS. 15 and 16, only one of the parallel arm resonator 56 and the series arm resonator 57 may be provided. For example, the parallel arm resonator 56 may be provided without the series arm resonator 57. Alternatively, the parallel arm resonator 56 may not be provided but the series arm resonator 57 may be provided. Furthermore, in addition to the parallel arm resonator 56 and the series arm resonator 57, other resonators or other capacitive elements may be provided.

[0090] The configuration of the fourth embodiment can be combined with the configurations of the second embodiment, the third embodiment, and the modified examples. For example, in the elastic wave device 10A of the second embodiment shown in FIGS. 9 and 10 , the series arm resonator 51 and the parallel arm capacitor 54 may be connected via another element. Alternatively, in the modified elastic wave device 10B of FIGS. 11 and 12 , the parallel arm resonator 52 and the series arm capacitor 53 may be connected via another element. Similarly, the elastic wave device 10C of the third embodiment may also include another element (a resonator or a capacitor).

[0091] 17 is a plan view of an elastic wave device according to a fifth preferred embodiment of the present invention. As shown in FIG. 17 , an elastic wave device 10E according to the fifth preferred embodiment of the present invention has a different configuration from the first preferred embodiment of the present invention in that the IDT electrodes 40, 40A are inclined.

[0092] The electrode fingers 41A and 42A of the IDT electrode 40A of the series arm capacitor 53 and the electrode fingers 41 and 42 of the IDT electrode 40 of the parallel arm capacitor 54 extend in a parallel direction. The electrode fingers 41A and 42A of the IDT electrode 40A and the electrode fingers 41 and 42 of the IDT electrode 40 extend in a direction inclined with respect to the extension direction of the upper electrode 31 and the lower electrode 32 of the series arm resonator 51 (extension direction of the connection portions 31c and 32c). For example, the IDT electrodes 40 and 40A are inclined at an angle θ (0<θ<90°) with respect to the Euler angle ψ of lithium niobate or lithium tantalate constituting the piezoelectric layer 20.

[0093] As a result, when the piezoelectric layer 20 is made of anisotropic lithium niobate or lithium tantalate, the IDT electrodes 40, 40A excite surface acoustic waves more effectively than in a configuration in which the IDT electrodes 40, 40A are provided in a direction parallel to or perpendicular to the direction in which the resonators are formed. Therefore, the IDT electrodes 40, 40A can effectively suppress unwanted waves generated from the series arm resonators 51 and the parallel arm resonators 52.

[0094] 17 shows a configuration in which both IDT electrodes 40, 40A are provided at an angle, but the present invention is not limited to this. A configuration in which either one of the IDT electrodes 40, 40A is provided at an angle may also be used. Furthermore, the configuration of the fifth embodiment can be combined with the configurations of the second to fourth embodiments and the modified examples described above.

[0095] 18 is a circuit diagram illustrating an elastic wave device according to a sixth embodiment. As shown in FIG. 18 , an elastic wave device 10F according to the sixth embodiment is a so-called ladder filter including series arm capacitive elements 53 and 58 and a parallel arm resonator 52.

[0096] The series arm capacitive elements 53 and 58 are connected in series between the input terminal 61 and the output terminal 62. One terminal of the parallel arm resonator 52 is connected to a signal path between the series arm capacitive element 53 and the series arm capacitive element 58, and the other terminal of the parallel arm resonator 52 is connected to a reference potential 63. In other words, in this embodiment, no resonator is provided in the series arm connecting the input terminal 61 and the output terminal 62.

[0097] In this embodiment, the series arm capacitive elements 53 and 58 and the parallel arm resonator 52 are connected to a common node N6. That is, one terminal of the series arm capacitive element 53 is connected to the input terminal 61, and the other terminal of the series arm capacitive element 53 is connected to the node N6. One terminal of the series arm capacitive element 58 is connected to the node N6, and the other terminal of the series arm capacitive element 58 is connected to the output terminal 62. Furthermore, one terminal of the parallel arm resonator 52 is connected to the node N6, and the other terminal of the parallel arm resonator 52 is connected to a reference potential 63.

[0098] The elastic wave device 10F of this preferred embodiment can suppress unwanted waves generated from the parallel arm resonator 52, as in the first preferred embodiment described above, and can also realize a wideband filter.

[0099] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0100] The present disclosure may also have the following configurations.

[0101] (1) An elastic wave device comprising: 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 provided on the first main surface or the second main surface of the piezoelectric layer and electrically connected to the resonator, the capacitive element having an IDT (Interdigital Transducer) electrode including a plurality of electrode fingers arranged in a predetermined direction. (2) The elastic wave device according to (1), wherein the resonator is a series arm resonator and the capacitive element is a parallel arm capacitive element, the series arm resonator is connected in series between an input terminal and an output terminal, one end of the parallel arm capacitive element is connected to a signal path between the input terminal and the output terminal, and the other end of the parallel arm capacitive element is connected to a reference potential. (3) The elastic wave device according to (2), wherein a resonant frequency of the IDT electrode of the parallel arm capacitor is approximately equal to a resonant frequency of the series arm resonator. (4) The elastic wave device according to (2) or (3), wherein the series arm resonator and the parallel arm capacitor have a common node. (5) The elastic wave device according to (4), wherein one of the upper electrode and the lower electrode of the series arm resonator is connected to the common node, and the parallel arm capacitor is provided in the same layer as one of the upper electrode and the lower electrode connected to the common node. (6) The elastic wave device according to (2) or (3), wherein the series arm resonator and the parallel arm capacitor are connected via another element. (7) The elastic wave device according to (1), wherein the resonator is a parallel arm resonator and the capacitive element is a series arm capacitive element, the series arm capacitive element is connected in series between an input terminal and an output terminal, one terminal of the parallel arm resonator is connected to a signal path between the input terminal and the output terminal, and the other terminal of the parallel arm resonator is connected to a reference potential. (8) The elastic wave device according to (7), wherein a resonant frequency of the IDT electrode of the series arm capacitive element substantially matches a resonant frequency of the parallel arm resonator. (9) The elastic wave device according to (7) or (8), wherein the parallel arm resonator and the series arm capacitive element have a common node.(10) The elastic wave device according to (9), wherein one of the upper electrode and the lower electrode of the parallel arm resonator is connected to the common node, and the series arm capacitive element is provided in the same layer as the one of the upper electrode and the lower electrode connected to the common node. (11) The elastic wave device according to (7) or (8), wherein the parallel arm resonator and the series arm capacitive element are connected via another element. (12) The elastic wave device according to (1), including a plurality of the resonators and a plurality of the capacitive elements, wherein the plurality of resonators include series arm resonators and parallel arm resonators, wherein the plurality of capacitive elements include series arm capacitive elements and parallel arm capacitive elements, wherein the series arm resonators are connected in series between an input terminal and an output terminal, wherein the series arm capacitive elements are connected in series between the input terminal and the output terminal and in parallel with the series arm resonators, wherein the parallel arm resonators are connected in parallel between a signal path between the input terminal and the output terminal and a reference potential, and wherein the parallel arm capacitive element is connected in parallel between the signal path between the input terminal and the output terminal and a reference potential and in parallel with the parallel arm resonators. (13) The elastic wave device according to (12), wherein a resonant frequency of an IDT electrode of the parallel arm capacitive element substantially matches a resonant frequency of the series arm resonator, and wherein the resonant frequency of the IDT electrode of the series arm capacitive element substantially matches a resonant frequency of the parallel arm resonator. (14) The elastic wave device according to (12) or (13), wherein the series arm resonator, the parallel arm resonator, the series arm capacitive element, and the parallel arm capacitive element have a common node. (15) The elastic wave device according to any one of (1) to (14), wherein the electrode fingers of the capacitive element extend in a parallel direction, and at least one of the plurality of electrode fingers extends in a direction oblique to an extending direction of the upper electrode and the lower electrode of the resonator. (16) The elastic wave device according to (1), wherein the elastic wave device includes a plurality of the capacitive elements, each of the plurality of capacitive elements being a series arm capacitive element, the plurality of series arm capacitive elements being connected in series between an input terminal and an output terminal, the resonator being a parallel arm resonator, one terminal of the parallel arm resonator being connected to a signal path between the plurality of series arm capacitive elements, and the other terminal of the parallel arm resonator being connected to a reference potential.(17) The acoustic wave device according to any one of (1) to (16), wherein the piezoelectric layer includes single crystal lithium niobate or lithium tantalate.

[0102] REFERENCE SIGNS LIST 10, 10A, 10B, 10C, 10D, 10E, 10F Acoustic wave device 11 Support substrate 12 Insulating layer 13 Support member 14, 15 Cavity portion 20 Piezoelectric layer 20a First main surface 20b Second main surface 31, 31A, 31B, 31C, 31D Upper electrode 32, 32A, 32B, 32C, 32D Lower electrode 40, 40A IDT electrode 51, 55, 57 Series arm resonator 52, 56 Parallel arm resonator 53, 58 Series arm capacitance element 54 Parallel arm capacitance element 61 Input terminal 62 Output terminal 63 Reference potential N1, N2, N3, N4, N5, N6 Node

Claims

1. An elastic wave device comprising: a piezoelectric layer having a first main surface and a second main surface opposite the first main surface, a resonator including 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 provided on the first main surface or the second main surface of the piezoelectric layer and electrically connected to the resonator, the capacitive element having an IDT (Interdigital Transducer) electrode including a plurality of electrode fingers arranged in a predetermined direction.

2. The elastic wave device according to claim 1, wherein the resonator is a series arm resonator and the capacitance element is a parallel arm capacitance element, the series arm resonator is connected in series between an input terminal and an output terminal, one terminal of the parallel arm capacitance element is connected to a signal path between the input terminal and the output terminal, and the other terminal of the parallel arm capacitance element is connected to a reference potential.

3. The elastic wave device according to claim 2, wherein a resonant frequency of the IDT electrode of the parallel arm capacitive element is approximately equal to a resonant frequency of the series arm resonator.

4. The elastic wave device according to claim 2, wherein the series arm resonator and the parallel arm capacitive element have a common node.

5. The elastic wave device according to claim 4, wherein one of the upper electrode and the lower electrode of the series arm resonator is connected to the common node, and the parallel arm capacitive element is provided in the same layer as one of the upper electrode and the lower electrode connected to the common node.

6. The acoustic wave device according to claim 2 or 3, wherein the series arm resonator and the parallel arm capacitive element are connected via another element.

7. The elastic wave device according to claim 1, wherein the resonator is a parallel arm resonator, the capacitance element is a series arm capacitance element, the series arm capacitance element is connected in series between an input terminal and an output terminal, one terminal of the parallel arm resonator is connected to a signal path between the input terminal and the output terminal, and the other terminal of the parallel arm resonator is connected to a reference potential.

8. The elastic wave device according to claim 7, wherein a resonant frequency of the IDT electrode of the series arm capacitive element is approximately equal to a resonant frequency of the parallel arm resonator.

9. The acoustic wave device according to claim 7, wherein the parallel arm resonator and the series arm capacitive element have a common node.

10. The elastic wave device according to claim 9, wherein one of the upper electrode and the lower electrode of the parallel arm resonator is connected to the common node, and the series arm capacitive element is provided in the same layer as one of the upper electrode and the lower electrode connected to the common node.

11. The elastic wave device according to claim 7 or 8, wherein the parallel arm resonator and the series arm capacitive element are connected via another element.

12. The elastic wave device according to claim 1, comprising a plurality of the resonators and a plurality of the capacitive elements, wherein the plurality of resonators include series arm resonators and parallel arm resonators, wherein the plurality of capacitive elements include series arm capacitive elements and parallel arm capacitive elements, wherein the series arm resonators are connected in series between an input terminal and an output terminal, the series arm capacitive elements are connected in series between the input terminal and the output terminal and in parallel with the series arm resonators, the parallel arm resonators are connected in parallel between a signal path between the input terminal and the output terminal and a reference potential, and the parallel arm capacitive elements are connected in parallel between the signal path between the input terminal and the output terminal and a reference potential, and in parallel with the parallel arm resonators.

13. The elastic wave device according to claim 12, wherein a resonant frequency of the IDT electrode of the parallel arm capacitive element is approximately equal to a resonant frequency of the series arm resonator, and a resonant frequency of the IDT electrode of the series arm capacitive element is approximately equal to a resonant frequency of the parallel arm resonator.

14. The elastic wave device according to claim 12, wherein the series arm resonator, the parallel arm resonator, the series arm capacitive element, and the parallel arm capacitive element have a common node.

15. An elastic wave device as claimed in any one of claims 1 to 14, wherein the electrode fingers of the capacitive element extend in a parallel direction, and at least one of the plurality of electrode fingers extends in a direction inclined with respect to the extension direction of the upper electrode and the lower electrode of the resonator.

16. The elastic wave device according to claim 1, comprising a plurality of the capacitance elements, each of the plurality of capacitance elements being series arm capacitance elements, the plurality of series arm capacitance elements being connected in series between an input terminal and an output terminal, the resonator being a parallel arm resonator, one terminal of the parallel arm resonator being connected to a signal path between the plurality of series arm capacitance elements, and the other terminal of the parallel arm resonator being connected to a reference potential.

17. The acoustic wave device according to any one of claims 1 to 16, wherein the piezoelectric layer contains single crystal lithium niobate or lithium tantalate.

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