US 12,255,604 B2
Acoustic wave device and filter
Mamoru Ishida, Tokyo (JP); and Takashi Matsuda, Tokyo (JP)
Assigned to TAIYO YUDEN CO., LTD., Tokyo (JP)
Filed by TAIYO YUDEN CO., LTD., Tokyo (JP)
Filed on Mar. 11, 2021, as Appl. No. 17/199,349.
Claims priority of application No. 2020-046698 (JP), filed on Mar. 17, 2020.
Prior Publication US 2021/0297055 A1, Sep. 23, 2021
Int. Cl. H03H 9/02 (2006.01); H03H 9/13 (2006.01); H03H 9/17 (2006.01); H03H 9/56 (2006.01); H03H 9/70 (2006.01)
CPC H03H 9/02086 (2013.01) [H03H 9/02031 (2013.01); H03H 9/13 (2013.01); H03H 9/173 (2013.01); H03H 9/175 (2013.01); H03H 9/176 (2013.01); H03H 9/562 (2013.01); H03H 9/564 (2013.01); H03H 9/568 (2013.01); H03H 9/706 (2013.01)] 17 Claims
OG exemplary drawing
 
1. An acoustic wave device comprising:
a piezoelectric layer having an upper surface and a lower surface, the piezoelectric layer being a rotated Y-cut lithium niobate substrate or an X-cut lithium tantalate substrate;
an upper conductive layer having a substantially consistent density, on or over the upper surface of the piezoelectric layer;
a lower conductive layer having a substantially consistent density, on or below the lower surface of the piezoelectric layer, a region where the upper conductive layer faces the lower conductive layer across the piezoelectric layer in a plan view defining a resonance region;
a first additional film having a substantially consistent density, disposed in at least one of the following locations: between the upper conductive layer and the piezoelectric layer, between the lower conductive layer and the piezoelectric layer, on an upper surface of the upper conductive layer, within the upper conductive layer as inserted therein, on a lower surface of the lower conductive layer, and within the lower conductive layer as inserted therein; and
a second additional film, above or below the piezoelectric layer, in each of one or more of lateral edges of the resonance region, imparting an additional mass to the upper conductive layer or the lower conductive layer, the second additional film being absent in a central area of the resonance region other than said one or more of the lateral edges,
wherein at least one of the upper and lower conductive layers is mainly made of ruthenium, chrome, copper, molybdenum, tungsten, tantalum, platinum, rhodium, or iridium, and
wherein at least a part of the first additional film is in the resonance region in the plan view, and the density of the first additional film is equal to or less than the density of aluminum.