A high temperature rapid thermal processing (HT-RTP) above 1400oC 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 O2, 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 O2 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 (Dit) of fabricated MOS capacitor shows 3-5x1011cm-2eV-1 at Ec-E~0.2eV. The field-effect channel mobility of fabricated 4H-SiC lateral MOSFETs was ~30cm2/Vs.