US 12,294,349 B2
Bulk acoustic wave devices with sandwich electrodes for higher resonant frequencies, and related fabrication methods
Juha Sakari Ella, Salo (FI); and Edgar Schmidhammer, Stein an der Traun (DE)
Assigned to RF360 Singapore Pte. Ltd., Singapore (SG)
Filed by RF360 Singapore Pte. Ltd., Singapore (SG)
Filed on Sep. 20, 2022, as Appl. No. 17/933,564.
Prior Publication US 2024/0097642 A1, Mar. 21, 2024
Int. Cl. H03H 9/02 (2006.01); H03H 3/02 (2006.01); H03H 9/13 (2006.01); H03H 9/56 (2006.01)
CPC H03H 9/02086 (2013.01) [H03H 3/02 (2013.01); H03H 9/131 (2013.01); H03H 9/568 (2013.01)] 12 Claims
OG exemplary drawing
 
1. An acoustic filter comprising:
a first bulk acoustic wave (BAW) device; and
a second BAW device;
wherein each of the first BAW device and the second BAW device comprises:
a piezoelectric layer;
a first electrode on a first side of the piezoelectric layer; and
a sandwich electrode on a second side of the piezoelectric layer, the sandwich electrode comprising:
a first layer of a first material having a first acoustic impedance; and
a second layer of a second material having a second acoustic impedance less than the first acoustic impedance, the second layer disposed between the first layer and the piezoelectric layer, wherein a first ratio of a thickness of the first layer to a thickness of the second layer of the sandwich electrode in the first BAW device is different than a second ratio of a thickness of the first layer to a thickness of the second layer of the sandwich electrode in the second BAW device.