We investigated the oxidation behaviors of poly Si1-xGex films with a 15% and 42% Ge content. The films were deposited using ultrahigh vacuum chemical vapor deposition on a 1000 A thick thermal SiO2 layer, and were oxidized using a conventional furnace in wet oxygen ambient at 700 and 800 degreesC. The physical and chemical properties of the oxide were analyzed by using Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy before and after the oxidation. We observed that the Ge content in the oxide layer and oxidation rate increased with the increase of Ge content in poly Si1-xGex films. We also observed that Ge content in the oxide layer decreased with the increase of oxidation temperature.