Silicon oxide(SiOx) films on GaN were synthesized at 75℃, using the inductively coupled plasma chemical vapor deposition(ICPCVD) with different radio-frequency chuck power(RF power). The physical and electrical properties of the deposited SiOx thin films were characterized by various methods. It is found that as the RF power increased, the films’ stress increased while the surface roughness and the film density increased. With optimized RF power, the SiOx/n-GaN metal-insulator-semiconductor(MIS) structures were fabricated. The electrical properties of the SiOx films were investigated by current density-voltage(J-V) and capacitance-voltage(C-V) measurements. The results show that the leakage current density is lower than 1×10-7A/cm2 at 90V, the minimum interface state density is 2.4×1010eV-1cm-2, indicating good electrical properties of ICPCVD deposited SiOx films.