US 12,308,825 B2
Transversely-excited film bulk acoustic resonators with narrow gaps between busbars and ends of interdigital transducer fingers
Bryant Garcia, Belmont, CA (US); and Filip ILiev, San Francisco, CA (US)
Assigned to MURATA MANUFACTURING CO., LTD, Nagaokakyo (JP)
Filed by MURATA MANUFACTURING CO., LTD, Nagaokakyo (JP)
Filed on Aug. 3, 2021, as Appl. No. 17/393,111.
Claims priority of provisional application 63/148,803, filed on Feb. 12, 2021.
Prior Publication US 2022/0263494 A1, Aug. 18, 2022
Int. Cl. H03H 9/54 (2006.01); H03H 3/02 (2006.01); H03H 9/02 (2006.01); H03H 9/205 (2006.01)
CPC H03H 9/54 (2013.01) [H03H 3/02 (2013.01); H03H 9/02015 (2013.01); H03H 9/02157 (2013.01); H03H 9/02228 (2013.01); H03H 9/205 (2013.01); H03H 2003/021 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A bulk acoustic resonator device comprising:
a substrate;
a piezoelectric layer attached directly, or indirectly via one or more intermediate layers, to the substrate, a portion of the piezoelectric layer over a cavity of the bulk acoustic resonator device;
an interdigital transducer (IDT) on the piezoelectric layer and having interleaved fingers,
wherein the interleaved fingers include a first plurality of fingers extending from a first busbar of the IDT and a second plurality of fingers extending from a second busbar of the IDT that opposes the first busbar,
wherein a center-to-center distance between at least a pair of adjacent interleaved fingers extending from the opposing first and second busbars defines a pitch of the IDT,
wherein the IDT includes a gap distance between an end of the first plurality of fingers and the second busbar, and/or between an end of the second plurality of fingers and the first busbar,
wherein the gap distance is less than ⅔ times the pitch, and
wherein a width of the interleaved fingers is not one-fourth an acoustic wavelength of the bulk acoustic resonator device at resonance frequency.