US 12,289,093 B2
Surface acoustic wave device and filter device
Masakazu Mimura, Nagaokakyo (JP)
Assigned to MURATA MANUFACTURING CO., LTD., Kyoto (JP)
Filed by Murata Manufacturing Co., Ltd., Nagaokakyo (JP)
Filed on Dec. 21, 2021, as Appl. No. 17/557,092.
Application 17/557,092 is a continuation of application No. PCT/JP2020/022676, filed on Jun. 9, 2020.
Claims priority of application No. 2019-116416 (JP), filed on Jun. 24, 2019.
Prior Publication US 2022/0116012 A1, Apr. 14, 2022
Int. Cl. H03H 9/02 (2006.01); H03H 9/145 (2006.01); H03H 9/64 (2006.01)
CPC H03H 9/02559 (2013.01) [H03H 9/14541 (2013.01); H03H 9/6483 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A surface acoustic wave device, comprising:
a piezoelectric substrate made of θ° rotated Y-cut X-propagation LiNbO3 having a cut angle θ;
an IDT electrode on the piezoelectric substrate and including a plurality of electrode fingers; and
a dielectric film on the piezoelectric substrate and covering the IDT electrode; wherein
the IDT electrode includes a main electrode layer and an auxiliary conductive layer;
the main electrode layer is, compared to the auxiliary conductive layer, closer to a side of the piezoelectric substrate;
the main electrode layer includes Pt as a main component; and
a relationship in Formula (1) and Equations (2A) to (2D) below is satisfied, where a film thickness of the main electrode layer is denoted as h, a film thickness of the dielectric film is denoted as H, and a wavelength determined by an electrode finger pitch of the IDT electrode is denoted as λ:
2×exp(−A×(θ+10.8))+B≤h/λ≤2×exp(−C×(θ+6.3))+D  Formula (1);
A=−0.1×(H/λ)+0.265  Equation (2A);
B=−0.2933×(H/λ)2+0.0613×(H/λ)+0.088  Equation (2B);
C=−0.2286×(H/λ)2−0.0257×(H/λ)+0.2642  Equation (2C); and
D=−0.5105×(H/λ)2+0.1448×(H/λ)+0.0872  Equation (2D).