Patent ID: 7701114

Claim:
A surface acoustic wave device comprising: an LiNbO 3 substrate having Euler angles (0°±5°, θ±5°, 0°±10°); an electrode provided on the LiNbO 3 substrate and including an IDT electrode primarily made of Cu; a first silicon oxide film provided in an area other than an area in which the electrode is arranged so as to have a thickness substantially equal to that of the electrode; and a second silicon oxide film arranged to cover the electrode and the first silicon oxide film; wherein the surface acoustic wave device utilizes an SH wave, wherein a duty D of the IDT electrode is at least about 0.52, and θ of the Euler angles (0°±5, θ±5°, 0°±10°) is set so as to fall within a range that satisfies the following Inequality (1A) or (1B): (1) when 0.52 ≦D≦ 0.6, (−10 ×D )+92.5−(100 ×C )≦θ≦(37.5 ×D 2 )−(57.75 ×D )+104.075+(5710 ×C 2 )−(1105.7 ×C )+45.729 Inequality (1A) (2) when D> 0.6, 86.5−(100 ×C )≦θ≦(37.5 ×D 2 )−(57.75 ×D )+104.075+(5710 ×C 2 )−1105.7 λC+ 45.729 Inequality (1B) where D is a duty, and C is a thickness of the IDT electrode normalized by a wavelength λ.