We have developed the oxidation method by atomic oxygen for the gate oxide formation in the SiC metal-oxide-semiconductor (MOS) devices. A mixture gas of oxygen (O-2)/ ozone (O-3) molecules is introduced into the oxidation furnace, where the atomic oxygen was formed by thermal decomposition of the O-3 molecules at elevated sample temperatures. Oxide growth rate (rox) during the oxidation process by the O-3 admixing gas is found to be the maximum around 5Torr at 950-1200degreesC, although the r(ox) by pure O-2 gas reveals the negligible r(ox), value below 50Torr at the same temperatures. This indicates that only atomic oxygen can contribute to form the oxide layer below 50Torr. Based on these results, MOS capacitors were fabricated at various temperatures maintaining the constant ambient pressure of 5Torr. Interface trapped density (D-it) evaluated by high-low capacitance-voltage (CV) measurements is found to largely depend on the oxidation temperature. The oxidation at 1200degreesC results in the significant reduction of the D-it. Consequently, the D-it near conduction band edge was reduced in the oxidation of atomic oxygen with compared to that of O-2.