SURFACE ACOUSTIC WAVE ELEMENT

摘要

PROBLEM TO BE SOLVED: To obtain a surface acoustic wave element which has satisfactory temperature characteristics since variance in propagation characteristics among surface acoustic waves is generated owing to unevenness in the joining strength of a substrate on its joined surface. SOLUTION: This element is equipped with a propagation substrate 11 which is a piezoelectric substrate, an auxiliary substrate 12 which is stacked on the propagation substrate 11 by direct joining, and interdigital electrodes 13, which are formed on the opposite surface of the propagation substrate 11 from the surface joined with the auxiliary substrate 12 and excite surface acoustic waves. The propagation substrate 11 and auxiliary substrate 12 are not joined together at least on the formation areas of the interdigitral electrodes 13 or right below a surface acoustic wave propagation area including the formation area of the interdigital electrodes 1 and 3, and the coefficient of thermal expansion of the auxiliary substrate 12 in the propagation direction of a surface acoustic wave is smaller than that of the propagation substrate 11.