Patent ID: 6875663

Claim:
A method of fabricating a semiconductor device comprising at least one kind of a MOS transistor on a semiconductor layer, and a trench isolation oxide film for defining at lest one active region as a region in which said MOS transistor is formed and electrically isolating said MOS transistor, comprising the steps of: (a) forming an auxiliary film for forming said trench isolation oxide film on said semiconductor layer; (b) forming a trench penetrating said auxiliary film and reaching a predetermined depth in said semiconductor layer; (c) forming said trench isolation oxide film by filling said trench with an oxide film and, after that, removing said auxiliary film on said active region by a predetermined thickness to thereby make said trench isolation oxide film project from a main surface of said auxiliary film; (d) implanting ions of an impurity of a conduction type different from that of a source/drain layer of said MOS transistor with energy by which the ions pass through said trench isolation oxide film and pass through the at least one active region, wherein after said step (c), a peak of a profile is formed in said semiconductor layer under said trench isolation oxide film and beneath the semiconductor layer under said active region; and (e) reducing the thickness of said trench isolation oxide film after formation of said channel stop layer.