An investigation of the structural and electrical properties of rapid thermal annealed silicon-silicon oxide (Si-SiO2) systems has been carried out. The oxide thickness is between 200-500 Angstrom. Infrared spectroscopy was used in the structural analysis. The electrical characterisations were carried out using the capacitance versus voltage (C-V) and the conductance versus voltage (G-V) methods. For the thermal oxides samples, it was found that in general, there is an increase in the number of fixed charges (N-f) after rapid thermal annealing (RTA). Sample annealed at 700 degrees C shows an increase in the interface trap density (D-it) as compared to the as-grown sample. For samples annealed at 900 degrees C and above, the Di, decreased as compared with the unannealed sample. For oxides prepared with the r.f. sputtering technique, it was observed that the as-prepared sample was very leaky and it was not possible to carry out the C-V or G-V measurements. However, after RTA the insulating property and D-it of the sputtered oxides improved significantly.