The C(0001¯) face of silicon carbide (SiC) has superior properties such as a faster oxidation ratio and a smoother surface compared with the Si(0001) face. We have investigated the oxidation and post-oxidation annealing effects on the capacitance–voltage and the interface state density (Dit) of n-type SiC metal–oxide–semiconductor (MOS) structures formed on the C(0001¯) face. It was found that pyrogenic oxidation and hydrogen annealing above 700 °C reduced Dit near the conduction-band edge. The value of Dit at Ec-E=0.2 eV is 1×1012 eV-1 cm-2, which is comparable with that of the MOS structure formed on the Si(0001) face. However, the value of Dit around the deep level at Ec-E=0.6 eV is one order of magnitude higher than that of n-type MOS structures formed on the Si(0001) face. It is very important to reduce Dit at the deep level for a high-quality SiO2/SiC interface on the 4H-SiC C(0001¯) face. © 2000 American Institute of Physics.