# US 12,763,752 B2 · Transversely-excited film bulk acoustic resonators with improved edge effects > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,763,752 B2 - Document ID: US12763752B2 - Status: Granted - Kind: B2 - Application number: 17/511,091 - Filed: 2021-10-26 - Published: 2022-05-26 - Granted: 2026-10-13 - Earliest claimed: 2020-11-23 - Assignees: Murata Manufacturing Co., Ltd. - Applicants: Murata Manufacturing Co., Ltd. - Inventors: Ventsislav Yantchev; Bryant Garcia - Web page: https://patentgrep.com/patent/US12763752B2 ## CPC - H03H 9/02228: {Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer} - H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) - H03H 9/02015: {Characteristics of piezoelectric layers, e.g. cutting angles} - H03H 9/02086: {Means for compensation or elimination of undesirable effects} - H03H 9/205: having multiple resonators (crystal tuning forks H03H9/21) - H03H 9/568: {consisting of a ladder configuration} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract Acoustic resonators, acoustic filter devices and methods of making the same. An acoustic resonator device includes a piezoelectric plate having front and back surfaces, an interdigital transducer (IDT) on the front surface including interleaved fingers, an overlapping distance of the interleaved fingers defining an aperture of the acoustic resonator device, and a modified acoustic velocity region proximate an edge of the aperture. ## Claims ### Claim 1 An acoustic resonator device comprising: a piezoelectric layer having front and back surfaces; an interdigital transducer (IDT) on the front surface comprising interleaved fingers extending from opposing busbars, an overlapping distance of the interleaved fingers defining an aperture of the acoustic resonator device; a modified acoustic velocity region proximate an edge of the aperture; and a dielectric layer on the piezoelectric layer and in the modified acoustic velocity region, wherein the dielectric layer is thinner in the modified acoustic velocity region than in a central portion of the aperture of the acoustic resonator device, wherein the acoustic resonator device further comprises a slow region adjacent the modified acoustic velocity region and proximate the edge of the aperture, and a strip of dielectric material on the piezoelectric layer over a portion of the interleaved fingers in the slow region, wherein the IDT further comprises at least one dummy finger in the modified acoustic velocity region between at least one interleaved finger of the interleaved fingers and one busbar of the opposing busbars, wherein the at least one dummy finger extends from the one busbar of the opposing busbars, and wherein a length of the at least one dummy finger corresponds to a distance between the at least one dummy finger and the at least one interleaved finger, wherein the interleaved fingers are disposed at a first portion of the piezoelectric layer and each of the opposing busbars are disposed at a second portion of the piezoelectric layer, and wherein a device thickness of the modified acoustic velocity region is thinner than device thicknesses of each of the first portion and the second portion. ### Claim 2 (depends on 1) The acoustic resonator device of claim 1, wherein the IDT further comprises a plurality of dummy fingers including the at least one dummy finger in the modified acoustic velocity region. ### Claim 3 (depends on 1) The acoustic resonator device of claim 1, wherein the interleaved fingers extend alternately from the opposing busbars, and wherein the modified acoustic velocity region is outside of the aperture and between an end of each interleaved finger of the interleaved fingers and one of the busbars of the opposing busbars. ### Claim 4 (depends on 1) The acoustic resonator device of claim 1, wherein the modified acoustic velocity region is configured to reduce acoustic energy leakage as compared to an acoustic resonator device without a modified acoustic velocity region. ### Claim 5 (depends on 1) The acoustic resonator device of claim 1, wherein: the opposing busbars include a first busbar and a second busbar, the interleaved fingers extend alternately from the first and second busbars, the modified acoustic velocity region extends from the first busbar towards the interleaved fingers extending from the second busbar, and the modified acoustic velocity region overlaps at least a portion of the interleaved fingers extending from the second busbar in a plan view of the first surface of the piezoelectric layer. ### Claim 6 (depends on 1) The acoustic resonator device of claim 1, wherein a pitch of the IDT is 2 to 20 times a thickness of the piezoelectric layer. ### Claim 7 (depends on 1) The acoustic resonator device of claim 1, wherein a pitch of the IDT is 3.3 to 5 times a width of the interleaved fingers. ### Claim 8 A filter device comprising: a piezoelectric layer having front and back surfaces; a conductor pattern on the front surface, the conductor pattern comprising a plurality of interdigital transducers (IDTs) of a respective plurality of resonators, each of the plurality of IDTs comprising interleaved fingers extending from opposing busbars, an overlapping distance of the interleaved fingers of each of the plurality of IDTs defining an aperture of a respective resonator of the plurality of resonators, wherein at least one resonator of the plurality of resonators comprises a modified acoustic velocity region proximate an edge of the aperture, and wherein the at least one resonator comprises a dielectric layer on the piezoelectric layer and in the modified acoustic velocity region, the dielectric layer being thinner in the modified acoustic velocity region than in a central portion of the aperture of the at least one resonator, wherein the at least one resonator further comprises a slow region adjacent the modified acoustic velocity region and proximate the edge of the aperture, and a strip of dielectric material on the piezoelectric layer over a portion of the interleaved fingers in the slow region, wherein the IDT of the at least one resonator further comprises at least one dummy finger in the modified acoustic velocity region between at least one interleaved finger of the interleaved fingers and one busbar of the opposing busbars, wherein the at least one dummy finger extends from the one busbar of the opposing busbars, and wherein a length of the at least one dummy finger corresponds to a distance between the at least one dummy finger and the at least one interleaved finger, wherein, for the at least one resonator, the interleaved fingers are disposed at a first portion of the piezoelectric layer and each of the opposing busbars are disposed at a second portion of the piezoelectric layer, and wherein, for the at least one resonator, a device thickness of the modified acoustic velocity region is thinner than device thicknesses of each of the first portion and the second portion. ### Claim 9 (depends on 8) The filter device of claim 8, wherein the IDT of the at least one resonator of the plurality of resonators further comprises a plurality of dummy fingers including the at least one dummy finger in the modified acoustic velocity region. ### Claim 10 (depends on 9) The filter device of claim 9, wherein the modified acoustic velocity region is configured to reduce acoustic energy leakage as compared to a resonator without a modified acoustic velocity region. ### Claim 11 (depends on 8) The filter device of claim 8, wherein the interleaved fingers of the at least one resonator of the plurality of resonators extend alternately from the opposing busbars, and wherein the modified acoustic velocity region is outside of the aperture and between an end of each interleaved finger of the at least one resonator and one of the busbars of the opposing busbars. ### Claim 12 (depends on 8) The filter device of claim 8, wherein, for the at least one resonator: the opposing busbars include a first busbar and a second busbar, the interleaved fingers extend alternately from the first and second busbars, the modified acoustic velocity region extends from the first busbar towards the interleaved fingers extending from the second busbar, and the modified acoustic velocity region overlaps at least a portion of the interleaved fingers extending from the second busbar in a plan view of the first surface of the piezoelectric layer. ### Claim 13 (depends on 8) The filter device of claim 8, wherein a pitch of the IDT of the at least one resonator is 2 to 20 times a thickness of the piezoelectric layer. ### Claim 14 (depends on 8) The filter device of claim 8, wherein a pitch of the IDT of the at least one resonator is 3.3 to 5 times a width of the interleaved fingers. ### Claim 15 A method of fabricating an acoustic resonator device comprising: forming an interdigital transducer (IDT) on a front side of a piezoelectric layer, the IDT comprising interleaved fingers extending from opposing busbars, an overlapping distance of the interleaved fingers defining an aperture of an acoustic resonator device; forming a modified acoustic velocity region proximate an edge of the aperture; forming a dielectric layer on the piezoelectric layer and in the modified acoustic velocity region; and forming a slow region adjacent the modified acoustic velocity region and proximate the edge of the aperture, and a strip of dielectric material on the piezoelectric layer over a portion of the interleaved fingers in the slow region, wherein the dielectric layer is thinner in the modified acoustic velocity region than in a central portion of the aperture of the acoustic resonator device, wherein the IDT is formed to further comprise at least one dummy finger in the modified acoustic velocity region between at least one interleaved finger of the interleaved fingers and one busbar of the opposing busbars, wherein the at least one dummy finger extends from the one busbar of the opposing busbars, and wherein a length of the at least one dummy finger corresponds to a distance between the at least one dummy finger and the at least one interleaved finger, wherein the interleaved fingers are disposed at a first portion of the piezoelectric layer and each of the opposing busbars are disposed at a second portion of the piezoelectric layer, and wherein a device thickness of the modified acoustic velocity region is thinner than device thicknesses of each of the first portion and the second portion. ### Claim 16 (depends on 15) The method of claim 15, further comprising forming a plurality of dummy fingers including the at least one dummy finger in the modified acoustic velocity region. ### Claim 17 (depends on 15) The method of claim 15, wherein the interleaved fingers extend alternately from the opposing busbars, and wherein the modified acoustic velocity region is outside of the aperture and between an end of each interleaved finger and one of the busbars of the opposing busbars. ### Claim 18 (depends on 15) The method of claim 15, wherein: forming the IDT comprises forming the IDT to include the interleaved fingers to extend alternately from the opposing busbars, and forming the modified acoustic velocity region comprises forming the modified acoustic velocity region to extend from a first busbar of the opposing busbars towards the interleaved fingers extending from a second busbar of the opposing busbars, and to overlap at least a portion of the interleaved fingers extending from the second busbar in a plan view of the first surface of the piezoelectric layer.