Patent ID: 6875643

Claim:
A manufacturing method of an SOI substrate having a partial SOI structure, in which a buried insulating film having a predetermined area is formed via an active layer in a part of a silicon single crystal substrate in plan view by ion-implanting elements to the part of the silicon single crystal substrate in plan view and then applying thereto a thermal processing, wherein a thickness of a peripheral edge portion of said buried insulating film is getting thinner toward a terminal edge of said buried insulating film, said method characterized in comprising: a masking film preparation step for preparing such a masking film that has an opening and is configured such that a thickness of said masking film in an edge portion defining and surrounding said opening is getting thinner toward the opening; a masking step for providing said masking film over a surface of said silicon single crystal substrate; an ion implantation step, subsequent to said masking step, for ion-implanting said elements from above the surface of said silicon single crystal substrate through said masking film to cause said elements to be bonded with the silicon in a predetermined depth; and a thermal processing step, subsequent to said ion implantation step, for applying the thermal processing to said silicon single crystal substrate to thereby form the buried insulating film in a location of a predetermined depth in said silicon single crystal substrate.