IP Library › Granted Patent US 12689354
Granted Patent B2
US 12689354 · App. 17/987,926 · Granted Jul 21, 2026

Acoustic wave device

Inventors: Katsuya Daimon (Nagaokakyo, JP); Koji Yamamoto (Nagaokakyo, JP)
Assignee: MURATA MANUFACTURING CO., LTD.
H03H9/25H03H9/02574H03H9/14541H03H9/1457
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Quick Facts
Patent No.
US 12689354
App. No.
17/987,926
Granted
Jul 21, 2026
Kind
B2
Abstract

An acoustic wave device includes a piezoelectric substrate and IDT electrodes each including a first pitch portion with a relatively wide electrode finger pitch and a second pitch portion with a relatively narrow electrode finger pitch. A central region is located on a central side in a direction in which electrode fingers extend, and first and second edge regions are located on both sides of the central region. Mass addition films are in the first and second edge regions and include first mass addition films in the first pitch portion and second mass addition films in the second pitch portion. A length of the first mass addition film along an acoustic wave propagation direction is greater than a length of the second mass addition film.

Claims (50)

1 . An acoustic wave device comprising:

a piezoelectric substrate; and

a plurality of interdigital transducer (IDT) electrodes extending in an acoustic wave propagation direction on the piezoelectric substrate and each including a pair of busbars and a plurality of electrode fingers; wherein

at least one of the plurality of IDT electrodes includes a first pitch portion in which an electrode finger pitch is relatively wide and a second pitch portion in which an electrode finger pitch is relatively narrow;

a portion in which the plurality of electrode fingers adjacent to each other overlap each other in the acoustic wave propagation direction is an intersecting region, the intersecting region includes a central region located on a central side in a direction in which the plurality of electrode fingers extend, and a pair of edge regions are provided on both sides of the central region in the direction in which the plurality of electrode fingers extend and including respective tip portions of the plurality of electrode fingers;

in each of the plurality of IDT electrodes, a pair of gap regions is between the intersecting region and the pair of busbars;

a plurality of mass addition films overlap portions of the plurality of electrode fingers in the pair of edge regions in a plan view;

the plurality of mass addition films includes a plurality of first mass addition films in the first pitch portion and a plurality of second mass addition films in the second pitch portion;

one of the plurality of first mass addition films overlaps at least one of the plurality of electrode fingers in a plan view;

each of the plurality of second mass addition films overlaps one of the plurality of electrode fingers but does not overlap another of the plurality of electrode fingers adjacent to the one of the plurality of electrode fingers in a plan view; and

a length of one of the plurality of first mass addition films along the acoustic wave propagation direction is greater than a length of one of the plurality of second mass addition films along the acoustic wave propagation direction.

2 . The acoustic wave device according to claim 1 , wherein a width of each of the plurality of electrode fingers in the second pitch portion in the pair of edge regions is equal to or less than a width of each of the plurality of electrode fingers in the central region.

3 . The acoustic wave device according to claim 1 , wherein each of the plurality of first mass addition films overlaps the plurality of electrode fingers in the first pitch portion and a portion located between the plurality of electrode fingers in a plan view.

4 . The acoustic wave device according to claim 1 , wherein each of the plurality of first mass addition films overlaps one of the plurality of electrode fingers but does not overlap another of the plurality of electrode fingers adjacent to the one of the plurality of electrode fingers in a plan view.

5 . The acoustic wave device according to claim 1 , wherein a length of the plurality of first mass addition film along the direction in which the plurality of electrode fingers extend is equal to a length of the plurality of second mass addition film along the direction in which the plurality of electrode fingers extend.

6 . The acoustic wave device according to claim 1 , wherein the plurality of mass addition films is on a side of the plurality of electrode fingers opposite to the piezoelectric substrate side.

7 . The acoustic wave device according to claim 6 , wherein

each of the plurality of mass addition films includes a first main surface in contact with one of the plurality of IDT electrodes, a second main surface facing the first main surface, and a side surface connected to the first main surface and the second main surface, the side surface being inclined with respect to a thickness direction of the mass addition film;

a protective film on the piezoelectric substrate covers the plurality of IDT electrodes and the plurality of mass addition films; and

in the protective film, a thickness of a portion covering the side surface of the mass addition film is less than a thickness of a portion covering the second main surface of the mass addition film, and a thickness of a portion directly covering the one of the plurality of IDT electrodes.

8 . The acoustic wave device according to claim 1 , wherein the plurality of mass addition films are between the plurality of electrode fingers and the piezoelectric substrate.

9 . The acoustic wave device according to claim 1 , wherein a plurality of cavities is provided at each of the pair of busbars of the plurality of IDT electrodes along the acoustic wave propagation direction.

10 . The acoustic wave device according to claim 1 , wherein

the piezoelectric substrate is a laminated substrate in which a support substrate, a high acoustic velocity film, a low acoustic velocity film, and a piezoelectric layer are laminated in this order;

an acoustic velocity of a bulk wave propagating through the low acoustic velocity film is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer; and

an acoustic velocity of a bulk wave propagating through the high acoustic velocity film is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer.

11 . The acoustic wave device according to claim 1 , wherein the acoustic wave device is a longitudinally coupled resonator acoustic wave filter further including a reflector provided on both sides of the plurality of IDT electrodes on the piezoelectric substrate in the acoustic wave propagation direction.

12 . An acoustic wave device comprising:

a piezoelectric substrate; and

a plurality of interdigital transducer (IDT) electrodes extending in an acoustic wave propagation direction on the piezoelectric substrate and each including a pair of busbars and a plurality of electrode fingers; wherein

at least one of the plurality of IDT electrodes includes a first pitch portion in which an electrode finger pitch is relatively wide and a second pitch portion in which an electrode finger pitch is relatively narrow;

a portion in which the plurality of electrode fingers adjacent to each other overlap each other in the acoustic wave propagation direction is an intersecting region, the intersecting region includes a central region located on a central side in a direction in which the plurality of electrode fingers extend, and a pair of edge regions are provided on both sides of the central region in the direction in which the plurality of electrode fingers extend and include respective tip portions of the plurality of electrode fingers;

in each of the plurality of IDT electrodes, a pair of gap regions is between the intersecting region and the pair of busbars;

a width of each of the plurality of electrode fingers in the first pitch portion in the pair of edge regions is greater than a width of each of the plurality of electrode fingers in the central region;

a width of each of the plurality of electrode fingers in the second pitch portion in the pair of edge regions is equal to or less than a width of each of the plurality of electrode fingers in the central region;

a plurality of mass addition films overlap portions of the plurality of electrode fingers in the first pitch portion and the second pitch portion located in the pair of edge regions in a plan view; and

each of the plurality of mass addition films overlaps the plurality of electrode fingers and a portion located between the plurality of electrode fingers in a plan view.

13 . The acoustic wave device according to claim 12 , wherein each of the plurality of mass addition films overlaps all the plurality of IDT electrodes in a plan view.

14 . The acoustic wave device according to claim 12 , wherein the plurality of mass addition films is on a side of the plurality of electrode fingers opposite to the piezoelectric substrate side.

15 . The acoustic wave device according to claim 14 , wherein

each of the plurality of mass addition films includes a first main surface in contact with one of the plurality of IDT electrodes, a second main surface facing the first main surface, and a side surface connected to the first main surface and the second main surface, the side surface being inclined with respect to a thickness direction of the mass addition film;

a protective film on the piezoelectric substrate covers the plurality of IDT electrodes and the plurality of mass addition films; and

in the protective film, a thickness of a portion covering the side surface of the mass addition film is less than a thickness of a portion covering the second main surface of the mass addition film, and a thickness of a portion directly covering the one of the plurality of IDT electrodes.

16 . The acoustic wave device according to claim 12 , wherein the plurality of mass addition films are between the plurality of electrode fingers and the piezoelectric substrate.

17 . The acoustic wave device according to claim 12 , wherein a plurality of cavities is provided at each of the pair of busbars of the plurality of IDT electrodes along the acoustic wave propagation direction.

18 . The acoustic wave device according to claim 12 , wherein

the piezoelectric substrate is a laminated substrate in which a support substrate, a high acoustic velocity film, a low acoustic velocity film, and a piezoelectric layer are laminated in this order;

an acoustic velocity of a bulk wave propagating through the low acoustic velocity film is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric layer; and

an acoustic velocity of a bulk wave propagating through the high acoustic velocity film is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer.

19 . The acoustic wave device according to claim 12 , wherein the acoustic wave device is a longitudinally coupled resonator acoustic wave filter further including a reflector provided on both sides of the plurality of IDT electrodes on the piezoelectric substrate in the acoustic wave propagation direction.