US 12,267,062 B2
Transversely-excited film bulk acoustic resonators with three-layer electrodes
Julius Koskela, Helsinki (FI); and Bryant Garcia, Burlingame, CA (US)
Assigned to Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Dec. 1, 2020, as Appl. No. 17/108,809.
Claims priority of provisional application 63/043,672, filed on Jun. 24, 2020.
Claims priority of provisional application 63/040,437, filed on Jun. 17, 2020.
Prior Publication US 2021/0399714 A1, Dec. 23, 2021
Int. Cl. H03H 9/13 (2006.01); H03H 9/02 (2006.01); H03H 9/17 (2006.01); H03H 9/56 (2006.01); H03H 3/02 (2006.01)
CPC H03H 9/131 (2013.01) [H03H 9/02228 (2013.01); H03H 9/174 (2013.01); H03H 9/564 (2013.01); H03H 9/568 (2013.01); H03H 2003/023 (2013.01)] 28 Claims
OG exemplary drawing
 
1. An acoustic resonator device comprising:
a substrate having a surface;
a piezoelectric layer attached to the surface of the substrate either directly or via one or more intermediate layers, the piezoelectric layer having a portion that forms a diaphragm that is over a cavity of the acoustic resonator device; and
an interdigital transducer (IDT) on a surface of the piezoelectric layer and having interleaved fingers on the diaphragm, the IDT configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm,
wherein the interleaved fingers comprise a first layer proximate the diaphragm, a second layer over the first layer, and a third layer over the second layer such that the second layer is between the first and third layers, wherein adjacent layers are comprised of different metals and a thickness of the second layer is in a range from 25% to 75% of a thickness of the diaphragm, and
wherein the primary shear acoustic mode is a bulk shear mode where acoustic energy propagates in a direction predominantly orthogonal to the surface of the piezoelectric layer and transverse to a direction of an electric field created by the interleaved fingers of the IDT that is predominantly lateral to the surface of the piezoelectric layer.