US-20260128731-A1 - ACOUSTIC WAVE FILTER DEVICE

US20260128731A1US 20260128731 A1US20260128731 A1US 20260128731A1US-20260128731-A1

Abstract

An acoustic wave filter device includes a series-arm resonator connected between an input terminal and an output terminal, a parallel-arm resonator connected between a ground terminal and a node on a path connecting the input terminal and the output terminal, and a capacitor connected between the input terminal and the output terminal. The capacitor is connected in parallel to the series-arm resonator. The acoustic wave filter device includes series-arm resonators. The capacitor is connected in parallel to the series-arm resonator connected to the input terminal of the series-arm resonators.

Inventors

Eiji Fujimori
Mitsuyuki Tanaka

Assignees

MURATA MANUFACTURING CO., LTD.

Dates

Publication Date: 20260507
Application Date: 20260106
Priority Date: 20230828

Claims (20)

1 . An acoustic wave filter device comprising: a series-arm resonator connected between an input terminal and an output terminal; a parallel-arm resonator connected between a ground terminal and a node on a path connecting the input terminal and the output terminal; and a capacitor connected between the input terminal and the output terminal; wherein the capacitor is connected in parallel to the series-arm resonator.
2 . The acoustic wave filter device according to claim 1 , further comprising: a plurality of the series-arm resonators; wherein the capacitor is connected in parallel to the series-arm resonator connected to the input terminal of the series-arm resonators.
3 . The acoustic wave filter device according to claim 1 , further comprising: a shield electrode connected to the ground terminal; wherein the shield electrode faces the capacitor.
4 . The acoustic wave filter device according to claim 2 , further comprising: a shield electrode connected to the ground terminal; wherein the shield electrode faces the capacitor.
5 . The acoustic wave filter device according to claim 1 , further comprising: a piezoelectric layer including a first main surface and a second main surface opposite to the first main surface; a support facing the second main surface of the piezoelectric layer; and a cover portion facing the first main surface of the piezoelectric layer; wherein the series-arm resonator and the parallel-arm resonator each include the piezoelectric layer, an upper electrode on the first main surface of the piezoelectric layer, and a lower electrode on the second main surface of the piezoelectric layer; and the capacitor is located on a surface of the cover portion facing the first main surface of the piezoelectric layer.
6 . The acoustic wave filter device according to claim 5 , further comprising: a first interelement connection electrode electrically connecting one end of the capacitor and one of the upper electrode and the lower electrode; and a second interelement connection electrode electrically connecting another end of the capacitor and another of the upper electrode and the lower electrode.
7 . The acoustic wave filter device according to claim 5 , further comprising: a shield electrode on an opposite side of the cover portion from the surface facing the first main surface of the piezoelectric layer; wherein the shield electrode is located in a region overlapping the capacitor.
8 . The acoustic wave filter device according to claim 5 , further comprising: a highly thermal conductive layer in a same layer as the piezoelectric layer on the support, the highly thermal conductive layer having a thermal conductivity higher than a thermal conductivity of the piezoelectric layer; wherein the piezoelectric layer is located at least in a region overlapping an excitation region in which the lower electrode, the piezoelectric layer, and the upper electrode are laminated; and the highly thermal conductive layer is located in a region around the excitation region.
9 . The acoustic wave filter device according to claim 2 , further comprising: a piezoelectric layer including a first main surface and a second main surface opposite to the first main surface; a support facing the second main surface of the piezoelectric layer; and a cover portion facing the first main surface of the piezoelectric layer; wherein the series-arm resonator and the parallel-arm resonator each include the piezoelectric layer, an upper electrode on the first main surface of the piezoelectric layer, and a lower electrode on the second main surface of the piezoelectric layer; and the capacitor is located on a surface of the cover portion facing the first main surface of the piezoelectric layer.
10 . The acoustic wave filter device according to claim 9 , further comprising: a first interelement connection electrode electrically connecting one end of the capacitor and one of the upper electrode and the lower electrode; and a second interelement connection electrode electrically connecting another end of the capacitor and another of the upper electrode and the lower electrode.
11 . The acoustic wave filter device according to claim 9 , further comprising: a shield electrode on an opposite side of the cover portion from the surface facing the first main surface of the piezoelectric layer; wherein the shield electrode is located in a region overlapping the capacitor.
12 . The acoustic wave filter device according to claim 9 , further comprising: a highly thermal conductive layer in a same layer as the piezoelectric layer on the support, the highly thermal conductive layer having a thermal conductivity higher than a thermal conductivity of the piezoelectric layer; wherein the piezoelectric layer is located at least in a region overlapping an excitation region in which the lower electrode, the piezoelectric layer, and the upper electrode are laminated; and the highly thermal conductive layer is located in a region around the excitation region.
13 . The acoustic wave filter device according to claim 3 , further comprising: a piezoelectric layer including a first main surface and a second main surface opposite to the first main surface; a support facing the second main surface of the piezoelectric layer; and a cover portion facing the first main surface of the piezoelectric layer; wherein the series-arm resonator and the parallel-arm resonator each include the piezoelectric layer, an upper electrode on the first main surface of the piezoelectric layer, and a lower electrode on the second main surface of the piezoelectric layer; and the capacitor is located on a surface of the cover portion facing the first main surface of the piezoelectric layer.
14 . The acoustic wave filter device according to claim 13 , further comprising: a first interelement connection electrode electrically connecting one end of the capacitor and one of the upper electrode and the lower electrode; and a second interelement connection electrode electrically connecting another end of the capacitor and another of the upper electrode and the lower electrode.
15 . The acoustic wave filter device according to claim 13 , further comprising: a shield electrode on an opposite side of the cover portion from the surface facing the first main surface of the piezoelectric layer; wherein the shield electrode is located in a region overlapping the capacitor.
16 . The acoustic wave filter device according to claim 13 , further comprising: a highly thermal conductive layer in a same layer as the piezoelectric layer on the support, the highly thermal conductive layer having a thermal conductivity higher than a thermal conductivity of the piezoelectric layer; wherein the piezoelectric layer is located at least in a region overlapping an excitation region in which the lower electrode, the piezoelectric layer, and the upper electrode are laminated; and the highly thermal conductive layer is located in a region around the excitation region.
17 . The acoustic wave filter device according to claim 5 , further comprising: a highly thermal conductive layer in a same layer as the piezoelectric layer on the support, the highly thermal conductive layer having a thermal conductivity higher than a thermal conductivity of the piezoelectric layer; a first interelement connection electrode electrically connecting one end of the capacitor and the upper electrode; and a second interelement connection electrode electrically connecting another end of the capacitor and the lower electrode; wherein the piezoelectric layer is located at least in a region overlapping an excitation region in which the lower electrode, the piezoelectric layer, and the upper electrode are laminated; and the highly thermal conductive layer is located in a region around the excitation region and is around the second interelement connection electrode.
18 . The acoustic wave filter device according to claim 17 , further comprising: a connector between the cover portion and the support; and a terminal on a surface of the cover portion opposite to the piezoelectric layer, the terminal being connected to the connector through a via passing through the cover portion; wherein the highly thermal conductive layer is located in a region overlapping the connector.
19 . The acoustic wave filter device according to claim 5 , wherein the piezoelectric layer includes single-crystal lithium niobate or lithium tantalate.
20 . The acoustic wave filter device according to claim 9 , wherein the piezoelectric layer includes single-crystal lithium niobate or lithium tantalate.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Japanese Patent Application No. 2023-137753 filed on Aug. 28, 2023 and is a Continuation application of PCT Application No. PCT/JP2024/028211 filed on Aug. 7, 2024. The entire contents of each application are hereby incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to acoustic wave filter devices. 2. Description of the Related Art International Publication No. 2017/110308, Japanese Unexamined Patent Application Publication No. 2016-152612, and Japanese Unexamined Patent Application Publication No. 2010-526456 describe acoustic wave devices (an electrical component in Japanese Unexamined Patent Application Publication No. 2010-526456) including a surface acoustic wave (SAW) element using a surface acoustic wave or a bulk acoustic wave (BAW) element using a bulk wave. For example, International Publication No. 2017/110308 discloses a configuration of the acoustic wave device in which an LC circuit is provided on a cover member. Such an acoustic wave device is required to be reduced in size and to satisfactorily adjust the bandpass characteristic. SUMMARY OF THE INVENTION Example embodiments of the present invention provide acoustic wave filter devices each with a reduced size and that are each able to satisfactorily adjust a bandpass characteristic. An acoustic wave filter device according to an example embodiment of the present invention includes a series-arm resonator connected between an input terminal and an output terminal, a parallel-arm resonator connected between a ground terminal and a node on a path connecting the input terminal and the output terminal, and a capacitor connected between the input terminal and the output terminal, the capacitor being connected in parallel to the series-arm resonator. The acoustic wave filter devices according to example embodiments of the present invention are each reduced in size and are each able to satisfactorily adjust the bandpass characteristic. The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram illustrating an acoustic wave filter device according to Example Embodiment 1 of the present invention. FIG. 2 is a plan view illustrating the acoustic wave filter device according to Example Embodiment 1 of the present invention. FIG. 3 is a plan view illustrating a portion of the acoustic wave filter device according to Example Embodiment 1 of the present invention. FIG. 4 is a sectional view taken along IV-IV′ in FIG. 3. FIG. 5 is a graph schematically illustrating the bandpass characteristics of acoustic wave filter devices according to an example and a comparative example. FIG. 6 is a graph schematically illustrating the impedance characteristics of series-arm resonators and parallel-arm resonators according to an example of an example embodiment of the present invention and a comparative example. FIG. 7 is a plan view illustrating an acoustic wave filter device according to Example Embodiment 2 of the present invention. FIG. 8 is a sectional view illustrating the acoustic wave filter device according to Example Embodiment 2 of the present invention. FIG. 9 is a plan view illustrating a portion of an acoustic wave filter device according to Example Embodiment 3 of the present invention. FIG. 10 is a sectional view taken along X-X′ in FIG. 9. FIG. 11 is a plan view illustrating a portion of an acoustic wave filter device according to a modified example of Example Embodiment 3 of the present invention. FIG. 12 is a sectional view illustrating an acoustic wave filter device according to Example Embodiment 4 of the present invention. DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS Example embodiments of the present invention will be described in detail below with reference to the drawings. The present invention is not limited by the example embodiments. The embodiments described in the present disclosure are merely examples, and the configurations of different example embodiments can be partially replaced or combined. From Example Embodiment 2 and in a modified example, points in common with Example Embodiment 1 are not described, and only different points are described. In particular, the same or similar advantageous effects resulting from the same or similar configurations are not described in each example embodiment. FIG. 1 is a circuit diagram illustrating an acoustic wave filter device according to Example Embodiment 1 of the present invention. Resonators of an acoustic wave filter device 10 according to Example Embodiment 1 are resonators using bulk waves, that is, bulk acoustic wave (BAW) elements, for example. As illustrated in FIG. 1, the acoustic wave filter d