COMPOSITE SUBSTRATE AND ELASTIC WAVE DEVICE

摘要

A composite substrate (10) is obtained by bonding a piezoelectric substrate (12) and a supporting substrate (14) that has a lower thermal expansion coefficient than the piezoelectric substrate (12). The supporting substrate (14) has a first surface (14a) that is bonded to the piezoelectric substrate (12) and a second surface (14b) that is on the reverse side of the first surface (14a). The thermal expansion coefficient of the supporting substrate (14) in the thickness direction gradually decreases from the second surface (14b) to the middle point (14c) between the first surface (14a) and the second surface (14b) in the thickness direction.