A novel low-temperature (<50°C) deposition process of a thin SiO2 film in a low-energy "rf hollow oval magnetron" system was studied. O2 is directly mixed with SiH4 and Ar for deposition under the low pressure (≲10 mTorr). The high electron density (1011 cm-3) and the high flux low energy (30 eV) ion bombardment greatly enhance the gas phase and surface processes. Uniform and dense thin films with smooth surface and good adhesion have been obtained. The film stoichiometry (from Si to SiO2), the index of refraction, and the film growth rate (from 1 to 35 Å/s) can be controlled by adjusting the SiH4 /O2 flow rates and their ratio.