SURFACE ACOUSTIC WAVE ELEMENT

摘要

PROBLEM TO BE SOLVED: To solve a problem of a conventional surface acoustic wave element that has had a limit of combinations of substrates because a thermal stress exerted on a layered substrate may cause a defect onto the layered substrate depending on a temperature at heat treatment for the purpose of laminating a propagation substrate and an auxiliary substrate through direct bonding. SOLUTION: The surface acoustic wave element of this invention is provided with a propagation substrate 11 made of a piezoelectric substrate, an auxiliary substrate 12 layered on the propagation substrate via an adhesive layer 14, and interdigital electrodes 13 that stimulate a surface acoustic wave and is formed on a side of the propagation substrate 11 opposite to the adhesive side. Selecting a glass transition point Tg of the cured adhesive 14 for -30 deg.C or over can obtain the surface acoustic wave element with an excellent temperature characteristic and a high degree of design freedom of the temperature characteristic without changing various characteristics of the piezoelectric substrate such as an electromechanical coupling coefficient.