Silicon-carbide offers great potential as a wide bandgap semiconductor for electronic applications. A good quality oxide dielectric will allow MOS device fabrication and in particular N-channel mosfets for their higher electron mobility. To date oxides on N-type silicon-carbide (nitrogen doped) have exhibited excellent characteristics while on P-type (aluminium or boron doped) the characteristics are poor. This paper presents results for the oxidation and subsequent nitridation of N and P-type silicon-carbide. It illustrates the role that nitrogen at the interface has in improving the trap densities and that nitric oxide provides the nitrogen well. Nitrous oxide, previously used to nitride silicon dioxide on silicon, is shown to substantially deteriorate the interface density of states for both N and P-type substrates.