High temperature (>1200degreesC) oxidation has been carried out to reduce the interface trap density and the residual carbon at MOS interface. The interface trap density Nit (equal to the integral of Dit) and the residual carbon of the oxide thermally grown at 1250degreesC (in dry O-2 ambient) are reduced by 60% and 40% as compared to those at 1080degreesC (in wet ambient), respectively. The interface trap density reduction is considered to be due to the reduction of the residual carbon at the MOS interface.