Method of making a semiconductor device having an SOI structure

摘要

Generation of parasitic transistor in active layer edge is prevented. In an NMOS region of a semiconductor layer (21) on an insulating film (20), boron ions are implanted by rotary oblique injection, using a nitride film (23) and a resist (253a) as mask. In the vicinity of a region for separating element by LOCOS method, that is, only in the edge region of the semiconductor layer (21) as the active layer of NMOS transistor, boron ions are implanted by about 3x1013/cm2. After LOCOS oxidation, the impurity concentration is heightened to such a level as the boron ions may not be sucked up into the oxide film.