Process for manufacturing a semi-conductor device of the type comprising at least one silicon layer deposited on an insulating substrate

A process for manufacturing a semi-conductor device comprising a step for depositing at least one layer of monocrystalline silicon on a flat substrate made from an insulating material, comprising a subsequent step for forming by oxidation a layer of silica of given thickness buried within the layer of monocrystalline silicon, one of the faces of the silica layer being in direct contact with one of the faces of the substrate, wherein the substrate is made from a monocrystalline material selected from those having a crystalline network topology of the same type as that of the silicon and chemically inert with respect to the silicon and materials used for depositing said silicon layer and wherein, with the depositing step comprising heat treatment at a temperature higher than the ambient temperature, the subsequent oxidation step takes place after this treatment by exposure to an oxygen containing environment during the time required for returning to ambient temperature, wherein the material forming said substrate is chosen from those having exclusive ionic conduction of the oxygen ion and the step forming the silica is achieved by oxidation of the silicon through the material forming the substrate by means of ionic conduction of the oxygen ions through said material in the region in contact with the surface of the substrate over said given thickness.