Polytype dependence of MOSFET performance in SiC(0001) was investigated. 4H-SiC MOSFETs showed a quite low channel mobility and a high threshold voltage, which seemed to be attributed to a high density of acceptor-like interface states and near-interface traps in SiO2 near the conduction band edge of 4H-SiC. The threshold voltage of 15R-SiC! MOSFETs was almost the same as of 6H-SiC MOSFETs, and the relation of channel mobility between 15R- and 6H-SiC is similar to the bulk mobility (15R-SiC is higher than GH-SiC), which indicates that the MOS interface properties are comparable for 15R- and GH-SiC. The oxidation ambient dependence of interface states is also discussed.