We systematically investigated the interface properties and reliability of NO nitrided SiC(11¯00) m-face MOS devices. Although nitridation at 1250°C improved the capacitance-voltage characteristics (i.e., flat-band voltage (V FB ) shift and hysteresis), the nitridation reduced the onset field of the Fowler-Nordheim current by about 1 MVcm -1 , causing a higher oxide leakage. Furthermore, the nitrided samples exhibited pronounced V FB shifts in response to both electron and hole injection under a high stress field condition (oxide field: ± 7–8 MVcm -1 ). In addition, when the bias stress condition was chosen on the basis of leakage current density instead of the oxide field, the V FB shifts became similar for samples with different nitridation durations. This indicates that the observed V FB shift is mainly caused by the carrier trapping into pre-existing traps. Our results clearly indicate the drawbacks of nitridation for m-face MOS devices in terms of oxide leakage and V FB instability.