PURPOSE: To enable the manufacture of a SOI substrate having a high heat- resisting adhesion layer, by forming a metal oxide film on junction surfaces of a plurality of substrates at a temperature of 500°C or less and adhering the substrates to each other and then performing heat treatment of them at a temperature of 500°C or more to obtain adhesion of them.

CONSTITUTION: A metal oxide film made of SiO2 or the like is formed on two substrates (a Si substrate, an insulating-material substrate, etc.), which are intended to be adhered, at a low substrate temperature of 500°C or less by a CVD or PVD method. Water is supplied to the surface of the formed metal oxide film so as to rinse this surface. A silanol group contributing to adhesion is effectively produced on the substrate surface in this process of forming the SiO film at the low temperature of 500°C or less. The junction surfaces, on which the metal oxide films are thus formed, are faced and adhered to each other, treated at a high temperature of 500°C or more so that stability in a sintering process of the adhesion layer can be realized. Hence, the stable adhesion layer with no distortion can be formed and high-quality crystallinity can be maintained in the obtained SOI substrate.