A high temperature rapid thermal processing (HT-RTP) above 1400° C was investigated for use in the gate oxide formation of 4H-SiC by a cold-wall oxidation furnace. The gate oxide film of ∼ 50nm can be formed for several minutes in the oxidizing atmospheres such as N2O and O-2, where the oxidation rates were 8-10nm/min. After the initial oxide formation, the HT-RTPs in various ambient gases were conducted, and the dependences of their MOS interface properties on the gases were evaluated by a capacitance-voltage (CV) measurement. Based on the results, the process sequence of gate oxidation was determined as follows; the initial oxide was formed by the HT-RTO (oxidation) in N2O or in O-2 with subsequent post annealing in Ar ambient, and then the HT-RTN (nitridation) in NO was conducted. The total process time becomes 20-50min. The interface trap density (D-it) of fabricated MOS capacitor shows 3-5 x 10(11)cm(-2) eV(-1) at E-c-E∼ 0.2eV. The field-effect channel mobility of fabricated 4H-SiC lateral MOSFETs was ∼ 30 cm(2)/Vs.