This work reports on the morphological, structural and electrical effects of a nitrous oxide (N 2 O) ambient post-oxidation annealing (POA) of the SiO 2/4H-SiC interface. In particular, a conventional electrical characterization of MOS capacitors showed that nitrous oxide POA reduces the presence of both fixed oxide charge and the density of interface states. A local atomically flat interface was observed by transmission electron microscopy with only a moderate step bunching observed at a macroscopic scale. A novel nanoscale characterization approach via scanning spreading resistance microscopy resolved local electrical changes induced at the SiC surface exposed to N 2 O POA. This result subsequently revealed additional insight into the mechanism for the improved device performance subjected to N 2 O POA treatment.