SEMICONDUCTOR DEVICE AND ITS MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a semiconductor device superior in high speed performance and its manufacturing method. SOLUTION: The manufacturing method comprises a step for forming single crystal silicon oxide island regions 13a and a surrounding oxide film 13b on an SOI substrate, a step for forming an oxide film 14 on island regions 13c, a step for laminating a second polycrystalline silicon layer 17 thereon, a step for covering this layer with a first insulation layer 20, etching it, selectively doping to form n-type collector parts 19, 29, a step for forming trenches reaching the island regions 13a, forming side walls 21a, 21b, a step for implanting ions therefrom to diffuse an n-type impurity, thereby forming emitter parts 15b, 27, forming oxide side walls 23a, 23b, implanting a p-type impurity to form base regions 28, filling base electrodes 24 in the trenches, laminating a second insulation layer, opening contact holes 26, and filling a wiring material therein.