Patent ID: 7425788

Claim:
A surface acoustic wave device comprising: a LiTaO 3 substrate including a plurality of grooves provided in an upper surface thereof; and an IDT electrode defined by Al disposed in the grooves provided in the upper surface of the substrate; and a SiO 2 layer arranged to cover the LiTaO 3 substrate and the IDT electrode; wherein the upper surface of the SiO 2 layer is flattened; the Euler angle of the LiTaO 3 substrate is within any one of the ranges provided in the Table below using λ as the wavelength of a surface acoustic wave; the film thickness of the IDT electrode is within the range indicated in the Table below that is associated with a corresponding range of the Euler angle of the LiTaO 3 substrate; and the thickness of the SiO 2 layer is within the range indicated in the Table below that is associated with a corresponding range of the film thickness of the IDT electrode: α = 0.05 or less θ of Euler angle (0, θ, 0) 0.125 <= SiO 2 layer thickness <= 0.20 0.02 <= Al thickness < 0.04 (0, 114° to 142°, 0) 0.04 <= Al thickness < 0.06 (0, 115° to 143°, 0) 0.06 <= Al thickness < 0.1 (0, 113° to 145°, 0) 0.1 <= Al thickness < 0.14 (0, 112° to 146°, 0) 0.20 <= SiO 2 layer thickness <= 0.275 0.02 <= Al thickness < 0.04 (0, 113° to 140°, 0) 0.04 <= Al thickness < 0.06 (0, 113° to 140°, 0) 0.06 <= Al thickness < 0.1 (0, 111° to 140°, 0) 0.1 <= Al thickness < 0.14 (0, 111° to 140°, 0) 0.275 <= SiO 2 layer thickness <= 0.35 0.02 <= Al thickness < 0.04 (0, 111° to 137°, 0) 0.04 <= Al thickness < 0.06 (0, 111° to 137°, 0) 0.06 <= Al thickness < 0.1 (0, 109° to 136°, 0) 0.1 <= Al thickness < 0.14 (0, 107° to 136°, 0) wherein, SiO 2 layer thickness and Al thickness are each normalized film thickness H/λ.