4H-SiC-oxide interfaces formed by various oxidation methods on SiC (0 0 0 1) Si-and (0 0 0 (1) over bar) C-face substrates have been characterized by performing spectroscopic ellipsometry in wide spectral region including deep UV spectral range and capacitance-voltage measurements. The results exhibit that the refractive indices of the interface layers well correlate with interface state density in all the cases of oxidation processes. To investigate the difference in interface characteristics between wet and dry oxidation, we compared to the sample fabricated by wet oxidation followed by heating in Ar or O-2 atmosphere, aiming to remove hydrogen related species at the interface. We also tried to make clear the difference in the interface characteristics between Si-and C-faces by lowering the oxidation rate of C-face down to those for Si-face. Putting together with all of the results obtained, we discuss the origins that determine the interface characteristics in terms of both the optical and electrical characterizations. (C) 2009 Elsevier B. V. All rights reserved.