The high density of interface states of thermally grown oxides on silicon carbide has prompted research into alternative oxidation methods and post oxidation anneals. One such alternative is oxidation of a deposited sacrificial silicon layer. A recent variation of this technique is a partial oxidation of the deposited Si layer, so that a thin Si layer remains between the SiO2 and SiC layers. If the SiO2/Si interface has lower interface state densities than the SiO2/SiC interface, the SiO2/Si/SiC hetero-structure could yield improved channel mobilities in MOS devices. Moreover, by correct optimization of the MOSFET device structure, breakdown can be designed to occur in the bulk SiC layer, thus maintaining a high blocking voltage. Post oxidation annealing in N2O is another technique often used to reduce interface state densities. However, little is known about the chemical and physical nature of these N2O oxidized dielectrics. Ellipsometric and Medium Energy Ion Scattering (MEIS) investigations of conventional SiO2/SiC interfaces compared with SiO2/Si/SiC hetero-junction structures and N2O oxidized samples are reported.