Effective improvement in electrical properties of NO passivated SiC/SiO2 interface after being irradiated by electrons is demonstrated. The density of interface traps after being irradiated by 100-kGy electrons decreases by about one order of magnitude, specifically, from 3×1012 cm-2?eV-1 to 4×1011 cm-2?eV-1 at 0.2 eV below the conduction band of 4H-SiC without any degradation of electric breakdown field. Particularly, the results of x-ray photoelectron spectroscopy measurement show that the C–N bonds are generated near the interface after electron irradiation, indicating that the carbon-related defects are further reduced.