In this study, SiO2-xFx films were deposited on Si and amorphous silicon, their physical and chemical properties were measured. An Al/ SiO2-xFx /Si and Al/ SiO2-xFx/a-Si/Si MOS structures were used for the electrical measurements. To improve the electrical properties, we investigated the characteristics of SiO2-xFx films after annealing in nitrogen and oxygen ambient. We can find the leakage current density can be reduced to about 1.09¡Ñ 10-6 A/cm2 and 1.03¡Ñ 10-7 at -1 MV/cm and at 1 MV/cm after annealing in oxygen ambient. Although the leakage current is improved one order but the dielectric constant is increase.