Semiconductor device and SOI substrate

A semiconductor device comprising a MOSFET which comprises,

• a gate insulating film provided on an active region defined by an element isolation insulating film provided in a main surface of a semiconductor substrate, and
• a gate electrode provided on said gate insulating film,
• said element isolation insulating film comprising,
• a trench formed in the main surface of said semiconductor substrate,
• an inner-wall insulating film provided on an inner wall of said trench and containing deuterium atoms, and
• an insulating film buried in said trench,
• wherein said trench is covered by said inner-wall insulating film.

A semiconductor device comprising at least a MOSFET provided on an SOI substrate comprising:

• a buried insulating film provided on a silicon substrate, and
• an SOI layer provided on said buried insulating film,
• wherein said buried insulating film is a two-layer film comprising any two of a silicon oxide film, a silicon oxynitride film and a silicon nitride film,
• one film of said two-layer film is formed on the other film of said two-layer film,
• one film of said two-layer film is thicker than the other film of said two-layer film, and
• said buried insulating film contains deuterium atoms.