The I-V characteristics of SiOx films deposited in an RF magnetron system with low pressure ( approximately 6 mTorr) SiH 4/O2/Ar gas mixtures have been studied. With the enhanced surface processes under the high flux, low energy ion bombardment, the substrate temperature (<50 degrees C) was lower than in other conventional plasma deposition processes (>300 degrees C). The film deposited under the optimum conditions without annealing has a very smooth surface, low leakage current (<10-10 A for F<6 MV cm-1) and high breakdown field strength (9-10 MV cm-1). It is found that the breakdown voltage is strongly correlated with the initial injection current. The film roughness, porosity and stoichiometry are the important factors for the electrical properties and can be controlled. The effects of RF power, deposition rate, and the oxygen to silane partial pressure ratio are investigated and discussed.