Patent ID: 8421314

Claim:
A composite substrate for a surface acoustic wave device, the composite substrate comprising: a piezoelectric substrate having anisotropy and which is capable of transmitting an elastic wave; and a support substrate having anisotropy and having a smaller thermal expansion coefficient than that of the piezoelectric substrate, and which is bonded thereto; wherein an in-plane maximum thermal strain amount, which is the largest thermal strain amount in the plane of the composite substrate, has a minimum value and a maximum value when the piezoelectric substrate and the support substrate are relatively rotated 0° to 360°; and wherein an entire surface of one surface of the piezoelectric substrate is bonded with an entire surface of one surface of the support substrate, and the piezoelectric substrate and the support substrate are thereby bonded directly or indirectly via an organic adhesive layer interposed therebetween, to each other so that the in-plane maximum thermal strain amount has the minimum value or a value in the vicinity thereof.