Composite substrate, piezoelectric device, and method for manufacturing composite substrate

Abstract

A composite substrate of the present disclosure is a composite substrate comprising a piezoelectric substrate and a sapphire substrate which are directly bonded, wherein the ratio of the number of oxygen atoms to the number of aluminum atoms in the bonding surface region including the bonding surface of the sapphire substrate bonded to the piezoelectric substrate is less than 1.5. The piezoelectric device of the present disclosure comprises the composite substrate. A method for manufacturing the composite substrate of the present disclosure comprises a step of preparing a piezoelectric substrate and a sapphire substrate, a step of heat-treating the sapphire substrate in a reducing atmosphere or in a vacuum, and a step of directly bonding the piezoelectric substrate to the sapphire substrate.

Dependencies are inferred from the claim text.