Patent ID: 8497190

Claim:
A process for providing an insulating layer of variable or discontinuous thickness in a semiconductor-on-insulator structure that initially includes, in succession a support substrate, an insulating layer of an oxide or oxynitride of a semiconductor material, and a thin semiconductor layer of the semiconductor material, wherein the process comprises: masking the surface of the thin layer to provide exposed regions and mask covered regions; applying a heat treatment to the structure in an inert or reducing atmosphere, and under controlled temperature and time conditions, so as to cause at least some oxygen in the insulating layer to diffuse through the exposed regions to thus reduce the thickness of the insulating layer beneath the exposed regions and form an insulating layer of non-uniform thickness; and before or during the application of the heat treatment, providing a surface layer of a nitride or oxynitride of the semiconductor material of the thin layer only on the exposed regions and at a thickness sufficient to slow down the rate of oxygen diffusion through the exposed regions while providing a faster rate of oxygen diffusion through the surface layer protected exposed regions than through the mask covered regions.