COMPOSITE SUBSTRATE FOR ELASTIC WAVE DEVICE, MANUFACTURING METHOD OF THE SAME, AND ELASTIC WAVE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a composite substrate capable of suppressing generation of spurious in an elastic wave device and having a simple configuration.SOLUTION: A composite substrate 10 for an elastic wave device is configured by sticking a piezoelectric substrate 12 to a support substrate 14. The piezoelectric substrate 12 is a substrate capable of propagating an elastic wave and has a spurious generation suppressing wave on its surface. In the spurious generation suppressing wave, an average length WSm of a curve element of the wave is 20 to 250 times the arrangement period of electrode fingers of IDT electrodes formed on the surface of the piezoelectric substrate 12, and a maximum height Wz of the wave is 0.2 to 1.5 times the arrangement period of the electrode fingers of the IDT electrode. The support substrate 14 has a thermal expansion coefficient smaller than that of the piezoelectric substrate 12 and is joined to the rear face of the piezoelectric substrate 12 by direct junction or joined to the rear face through an organic adhesive layer.