A novel hydrogen sensor based on Pd/SiO2/SiC capacitors with field oxide ramp termination was fabricated, and a systematic investigation of the most utilized post oxidation annealing (POA) processes, in N or P based ambient, was realized in order to propose the most appropriate technological approach. The experimental structures were electrically characterized, on the one hand to examine the gate oxide quality and, on the other hand, to test the device response as hydrogen sensor. We demonstrated that, whereas the POCl3 based POA leads to significant improvement of the SiO2/SiC interface, and moreover of the oxide breakdown electric field, the 1100°C N2 based POA assures the highest response as hydrogen sensor, both at room temperature and 200°C. Both interface states density and oxide charges present in the MOS structures have been determined and their influence on the observed phenomena have been discussed.