The oxidation of polycrystallineSixGe1−xfilms with different compositions (i.e., different values ofx) is carried out in pyrogenic steam at 800 °C for various lengths of time. It is found that the oxidation is enhanced by the presence of germanium and that the enhancement effect is more pronounced for the films richer in germanium. A mixed oxide in the form of either(Si,Ge)O2orSiO2–GeO2is found at the sample surface if the initialSixGe1−xcontains more than 50&percent; of germanium. However, a surface silicon cap layer of about 14 nm is found to have a significant impact on the oxidation of theSi0.5Ge0.5films; it leads to the growth of about 115-nm-thickSiO2which is about four times that of theSiO2resulting from the oxidation of the cap layer itself. On theSixGe1−xfilms with only 30&percent; of germanium, theSiO2continues to grow after oxidation for 180 min resulting in 233-nm-thickSiO2which is about 2.4 times greater than theSiO2grown on ⟨100⟩ silicon substrates. Rejection of germanium results in piling up of germanium at the interface between the growingSiO2and the remainingSixGe1−x.Substantial interdiffusion of silicon and germanium takes place in the remainingSixGe1−x.The experimental results are discussed in terms of thermodynamics and kinetics. ©1997 American Institute of Physics.