FABRICATION OF SEMICONDUCTOR DEVICE

PURPOSE:To obtain a semiconductor device having an insulating film excellent in electric characteristics without causing any damage on the steep impurity distribution and iGe/Si heterojunction by depositing an oxide, containing a semiconductor substrate as once component, on the semiconductor substrate including an impurity layer having specified impurity distribution in an oxygen atmosphere containing steam. CONSTITUTION:A gate oxide 15 is deposited by 5nm through wet oxidation on an n-type Si layer 14 embedded with a B layer 13 at a depth of 50nm from the surface. More specifically, boron 13 is adsorbed selectively to the exposed part of Si on a P-type Si substrate 11 isolated by an oxide 12 using B2H6 gas. Subsequently, an Si layer 14 doped with boron by 5X10 /cm is grown selectively by 50nm at the expose part of Si using silane and diborane. An SiO2 gate oxide 15 is then deposited by 5nm by wet oxidation. This method allows deposition of gate oxide of 5nm thick or less by highly reliable thermal oxidation without causing any damage on the impurity distribution.