Patent ID: 7187101

Claim:
A surface acoustic wave filter comprising: a piezoelectric substrate; and an input-side IDT electrode and an output-side IDT electrode arranged on the piezoelectric substrate so as to be separated from each other in the propagation direction of a surface acoustic wave; wherein the piezoelectric substrate is a crystal substrate; the input-side IDT electrode and the output-side IDT electrode each include an electrode layer made of Al or an Al alloy defining a major electrode layer, and the electrode film thickness ratio h/λ is in the range of from about 0.035 to about 0.06, wherein h represents the film-thickness of the input-side IDT electrode and the output-side IDT electrode, and λ represents the wavelength of the surface acoustic wave; at least one of the input-side IDT electrode and the output-side IDT electrode is an SPUDT electrode; and the crystal substrate is an ST-cut crystal substrate having an Euler's angle (0, θ, 0), and the angle θ is in the range represented by θ={−3·(h/λ)×100+134}±1.