Semiconductor device

Patent Granted A film with small hysteresis and high voltage resistance is obtained by reducing the carbon content in a gate insulating film on a SiC substrate. Specifically, the carbon content in the gate insulating film is set to 1x10<20 >atoms/cm<3 >or less. For this, using a plasma processing apparatus, a silicon oxide film is formed on the SiC substrate and then the formed silicon oxide film is reformed by exposure to radicals containing nitrogen atoms. Thus, the gate insulating film excellent in electrical properties is obtained.