Surface acoustic wave element

摘要

Disclosed is a SAW element with a propagation substrate that is a piezoelectric substrate. An auxiliary substrate is laminated on one surface of the propagation substrate by way of direct bonding, and a comb-shaped electrode is formed on another surface of the propagation substrate that is opposite the surface with the auxiliary substrate. The electrode excites an acoustic wave. The propagation substrate and the auxiliary substrate are not bonded to each other in at least a region immediately below a region where the comb-shaped electrode is formed. A coefficient of thermal expansion in a propagation direction of the acoustic wave of the auxiliary substrate is smaller than a coefficient of thermal expansion in a propagation direction of the acoustic wave of the propagation substrate.