Patent ID: 7989308

Claim:
A method for manufacturing, forming or creating at least one dielectrically insulating trench ( 10 ) comprising rounded edges ( 14 ) of active silicon layer portions ( 6 , 7 ; 3 ) adjacent to the trench, each of said rounded edges ( 14 ) located at a respective transition area ( 14 ) connecting to a buried insulating layer ( 2 ) of an SOI structure, said method comprising performing an etch process consisting of two steps, wherein in the first step of the etch process said trench ( 10 ) is etched to the insulating layer ( 2 ); in the second step of the etch process under-etched regions ( 12 ) are formed on sidewalls of the trench ( 10 ) by isotropically etching a part of the insulating layer ( 2 ), said under-etched regions having a width and a depth that correspond approximately to half of a thickness of said buried insulating layer; after performing said etch process thermally oxidizing surfaces of said trench ( 10 ) and said under-etched regions ( 12 ).