This work presents the structural and electrical results of rapid thermal oxidation of radio frequency sputtered polycrystalline Si1-xGe. thin films. The atomic force microscopy results show Ge island sizes between 175 and 215 mn. The Fourier transform infrared and X-ray photoelectron spectroscopy measurements reveal the formation of GeO2 in oxidized polycrystalline Si0.6Ge0.39 and GeO2 plus GeOx in oxidized polycrystalline Si0.73Ge0.27 samples. The MOS capacitors fabricated from the polycrystalline Si-0.61 Ge-0.39 film exhibit a lower leakage current and a higher breakdown voltage compared to those fabricated from polycrystalline Si0.73Ge0.27 substrate. The interface trap density and fixed oxide charge density were also found to be lower for the MOS capacitor fabricated from the polycrystalline Si-0.61 Ge-0.39 film.