Patent ID: 6879225

Claim:
A surface acoustic wave device comprising: a Y-cut, X-propagation LiTaO 3 substrate; at least one interdigital transducer provided on the LiTaO 3 substrate and made of Al or a metal containing Al as a major component; and an SiO 2 film arranged on the surface of the LiTaO 3 substrate so as to cover the at least one interdigital transducer; wherein the thickness Hs of the SiO 2 film normalized by the wavelength λ of a surface acoustic wave and the cut angle θ of the LiTaO 3 substrate are set to be in any one of the ranges represented by formula (1) to (8): in the case of 0.00< Hs≦ 0.05, 30°<θ<36° (1) in the case of 0.05< Hs≦ 0.10, 29°<θ<36° (2) in the case of 0.10< Hs≦ 0.15, 28°<θ<36° (3) in the case of 0.15< Hs≦ 0.20, 27°<θ<36° (4) in the case of 0.20< Hs≦ 0.25, 26°<θ<36° (5) in the case of 0.25< Hs≦ 0.30, 25°<θ<35° (6) in the case of 0.30< Hs≦ 0.35, 23°<θ<34° (7) in the case of 0.35< Hs≦ 0.40, 21°<θ<31° (8).