Gate leakage current and constant-voltage time-dependent dielectric breakdown (TDDB) measurements at room temperature and elevated temperatures of commercially available large-area 1.2 kV 4H-SiC power MOSFETs are performed to investigate their gate oxide reliability and better understand their failure modes. It is shown that Fowler-Nordheim (F-N) tunneling current is the dominant mechanism contributing to the gate leakage current. Despite anomalous gate leakage current behaviors that could be caused by interface states densities ( Dit)and near interface oxide traps, leakage currents at normal operating condition ( VG=20 V at 28°C) are less than 100 pA for all vendors. Extrapolation from TDDB measurements shows that the predicted lifetimes when VG=20V at both 28°C and 175°C are far longer than the targeted 10 years.