Patent ID: 6958266

Claim:
A method of manufacturing a semiconductor device, comprising the steps of: (a) providing an SOI substrate having an SOI structure including a semiconductor substrate, a buried insulation layer, and an SOI layer; (b) selectively removing said SOI layer from above a top surface thereof so as not to penetrate said SOI layer, to form a plurality of trenches, whereby regions of said SOI layers which lie between said plurality of trenches serve as a plurality of device formation regions; (c) filling each of said plurality of trenches with an insulation film, said insulation film in at least one of said plurality of trenches and part of said SOI layer which underlies said at least one of said plurality of trenches constituting a partial isolation region; and (d) forming a predetermined device in each of said plurality of device formation regions, wherein said plurality of trenches include a first trench and a second trench, and said at least one of said plurality of trenches includes said first trench, said method further comprising the step of (e) further removing said SOI layer from a bottom portion of said second trench to cause said second trench to extend through said SOI layer, said step (e) being performed after said step (b) and before said step (c), wherein said step (e) causes said insulation film in said first trench and part of said SOI layer which underlies said first trench to constitute said partial isolation region, and causes said insulation film in said second trench extending through said SOI layer to constitute a complete isolation region.