Patent ID: 7564100

Claim:
A silicon on sapphire wafer, comprising: a sapphire substrate; a polysilicon layer which is provided on a back surface of the sapphire substrate and which is non-transparent; a stress relaxing film which is provided on the polysilicon layer, which consists of a silicon nitride film having Si—H bonds and having a Si—H concentration of 10×10 21 /cm 3 or less determined from an infrared absorption peak, and which is in a state of compressive stress due to the Si—H concentration; and a silicon nitride layer which is provided on the stress relaxing film and which is in a state of tensile stress wherein the tensile stress of the silicon nitride layer is set so as to be cancelled by the compressive stress of the silicon nitride film so that warping of the silicon on sapphire wafer is reduced or prevented.