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US-20260128721-A1 - ACOUSTIC WAVE DEVICE

US20260128721A1US 20260128721 A1US20260128721 A1US 20260128721A1US-20260128721-A1

Abstract

An acoustic wave device includes a resonator including a piezoelectric layer including first and second main surfaces opposed to each other, 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 a capacitor including an upper interdigital transducer (IDT) electrode on the first main surface of the piezoelectric layer, and a lower IDT electrode on the second main surface of the piezoelectric layer. The capacitor is connected in parallel with the resonator. The upper IDT electrode and the lower IDT electrode of the capacitor are electrically connected to one another.

Inventors

  • Katsuhito Kuroda

Assignees

  • MURATA MANUFACTURING CO., LTD.

Dates

Publication Date
20260507
Application Date
20260106
Priority Date
20230905

Claims (16)

  1. 1 . An acoustic wave device comprising: a resonator including: a piezoelectric layer including a first main surface and a second main surface opposite to the first main surface; 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 a capacitor including: an upper interdigital transducer (IDT) electrode on the first main surface of the piezoelectric layer; and a lower IDT electrode on the second main surface of the piezoelectric layer; wherein the capacitor is connected in parallel with the resonator; and the upper IDT electrode and the lower IDT electrode of the capacitor are electrically connected to one another.
  2. 2 . The acoustic wave device according to claim 1 , wherein each of the upper IDT electrode and the lower IDT electrode includes a plurality of electrode fingers arranged in a predetermined direction; the plurality of electrode fingers of the upper IDT electrode are opposed to the plurality of electrode fingers of the lower IDT electrode with the piezoelectric layer interposed therebetween; and a same electric potential is supplied to an electrode finger of the upper IDT electrode and an electrode finger of the lower IDT electrode opposed to one another with the piezoelectric layer interposed therebetween.
  3. 3 . The acoustic wave device according to claim 1 , wherein each of the upper IDT electrode and the lower IDT electrode includes a plurality of electrode fingers arranged in a predetermined direction; the plurality of electrode fingers of the upper IDT electrode are opposed to the plurality of electrode fingers of the lower IDT electrode with the piezoelectric layer interposed therebetween; and different electric potentials are supplied to an electrode finger of the upper IDT electrode and an electrode finger of the lower IDT electrode opposed to one another with the piezoelectric layer interposed therebetween.
  4. 4 . The acoustic wave device according to claim 1 , wherein the upper IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers arranged in an alternating manner in a predetermined direction; the lower IDT electrode includes a plurality of third electrode fingers and a plurality of fourth electrode fingers arranged in an alternating manner in the predetermined 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 to one another through a first via penetrating 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 to one another through a second via penetrating the piezoelectric layer.
  5. 5 . The acoustic 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 another one of the upper electrode and the lower electrode of the resonator.
  6. 6 . The acoustic wave device according to claim 1 , further comprising: a plurality of the resonators, wherein the plurality of resonators include a series arm resonator and a parallel arm resonator; the series arm resonator is connected between an input terminal and an output terminal in series; the parallel arm resonator is connected between a signal path between the input terminal and the output terminal and a reference potential in parallel; and the capacitor is connected in parallel with the series arm resonator and is connected between the input terminal and the output terminal in series.
  7. 7 . The acoustic wave device according to claim 1 , further comprising: a plurality of the resonators; wherein the plurality of resonators include a series arm resonator and a parallel arm resonator; the series arm resonator is connected between an input terminal and an output terminal in series; the parallel arm resonator is connected between a signal path between the input terminal and the output terminal and a reference potential in parallel; and the capacitor is connected in parallel with the parallel arm resonator, one terminal of the capacitor is connected to the signal path between the input terminal and the output terminal, and another terminal of the capacitor is connected to the reference potential.
  8. 8 . The acoustic wave device according to claim 1 , wherein the piezoelectric layer includes a single crystal of lithium niobate or lithium tantalate.
  9. 9 . The acoustic wave device according to claim 1 , wherein the resonator is configured to utilize a bulk wave.
  10. 10 . The acoustic wave device according to claim 1 , further comprising a support opposed to the second main surface of the piezoelectric layer.
  11. 11 . The acoustic wave device according to claim 10 , wherein the support includes a support substrate and an insulating layer provided between the support substrate and the piezoelectric layer.
  12. 12 . The acoustic wave device according to claim 11 , wherein the support substrate includes silicon or quartz.
  13. 13 . The acoustic wave device according to claim 11 , wherein the insulating layer includes silicon oxide.
  14. 14 . The acoustic wave device according to claim 1 , wherein the support includes a cavity portion opposed to the second main surface of the piezoelectric layer.
  15. 15 . The acoustic wave device according to claim 1 , wherein a thickness of the piezoelectric layer is about 1 μm or less.
  16. 16 . The acoustic wave device according to claim 1 , wherein each of the upper and lower electrodes includes aluminum, platinum, copper, tungsten, or molybdenum, or an alloy including at least one of aluminum, platinum, copper, tungsten, or molybdenum.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to Japanese Patent Application No. 2023-143875 filed on Sep. 5, 2023 and is a Continuation Application of PCT Application No. PCT/JP2024/025102 filed on Jul. 11, 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 devices. 2. Description of the Related Art U.S. Patent Application Publication No. 2019/0273478 discloses an acoustic wave device including a bulk acoustic wave (BAW) element utilizing a bulk wave. The acoustic wave device in U.S. Patent Application Publication No. 2019/0273478 includes a Lamb-wave loop circuit that generates an anti-phase to a target signal at a particular frequency, and the Lamb-wave loop circuit includes an IDT electrode. Such an acoustic wave device is required to have a reduced size and to favorably adjust bandpass characteristics. In U.S. Patent Application Publication No. 2019/0273478, the IDT electrode included in the Lamb-wave loop circuit is provided for Lamb-wave excitation, and formation of a desired electrostatic capacitance by the IDT electrode included in the Lamb-wave loop circuit is not considered. SUMMARY OF THE INVENTION Example embodiments of the present invention provide acoustic wave devices each with a reduced size and improved bandpass characteristics. An acoustic wave device according to an example embodiment of the present invention includes a resonator including a piezoelectric layer including a first main surface and a second main surface opposite to the first main surface, 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 a capacitor including an upper interdigital transducer (IDT) electrode on the first main surface of the piezoelectric layer, and a lower IDT electrode on the second main surface of the piezoelectric layer. The capacitor is connected in parallel with the resonator. The upper IDT electrode and the lower IDT electrode of the capacitor are electrically connected to one another. Acoustic wave devices according to example embodiments of the present invention each have a reduced size and improved bandpass characteristics. 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 perspective view of an acoustic wave device according to a first example embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II′ in FIG. 1. FIG. 3 is an explanatory diagram illustrating capacitances generated in a capacitor according to the first example embodiment of the present invention. FIG. 4 is a sectional view of an acoustic wave device according to a second example embodiment of the present invention. FIG. 5 is an explanatory diagram illustrating capacitances generated in a capacitor according to the second example embodiment of the present invention. FIG. 6 is a circuit diagram illustrating an acoustic wave device according to a third example embodiment of the present invention. FIG. 7 is a graph illustrating bandpass characteristics of acoustic wave devices according to Example 1 and Comparative Examples 1 and 2. FIG. 8 is a circuit diagram illustrating an acoustic wave device according to a fourth example embodiment of the present invention. FIG. 9 is a graph illustrating bandpass characteristics of acoustic wave devices according to Example 2 of an example embodiment of the present invention and Comparative Examples 1 and 3. DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS Hereinafter, example embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to these example embodiments. Each example embodiment described in the present disclosure is illustrative, and configurations of different example embodiments can be partially replaced or combined with one another. In a modification and a second example embodiment and thereafter, description of matters in common with a first example embodiment will be omitted, and only different points will be described. Particularly, the same or similar operations and advantageous effects provided by similar configurations will not be described individually in each example embodiment. FIG. 1 is a perspective view of an acoustic wave device according to a first example embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II′ in FIG. 1. As illustrated in FIGS. 1 and 2, an acoustic wave device 10 includes a support 13, a piezoelectric layer 20, a resonator 30, and a capacitor 40. The resonator 30 utilizes a bulk wave, that is, a bulk acoustic wav