To provide a surface acoustic wave device which uses an in-plane rotated ST cut quarts crystal plate around an Z'-axis, and which has a large reflectioncoefficient of a Rayleigh wave. Z’軸まわりに面内回転させたSTカット水晶板を用いるとともに、Rayleigh波の反射係数が大きな弾性表面波装置を提供する。 - 特許庁