A mathematical model of oxidation ofSixGe1−xalloys is presented. The growth ofSiO2is simulated in conjunction with the determination of silicon distribution inSixGe1−xusing numerical methods. The main feature of the model is the assumption of simultaneous oxidation of germanium and silicon when exposing theSixGe1−xto an oxidizing atmosphere. In accordance with thermodynamics, theGeO2formed is subsequently reduced by the (free) silicon available at the interface between the growingSiO2and the remainingSixGe1−xthrough a reduction reaction. Thus, the enhanced oxidation of silicon in the presence of germanium is modeled as a result of the rapid oxidation of germanium followed by the quick reduction ofGeO2by silicon. The growth of a mixed oxide in the form of either(Si,Ge)O2orSiO2–GeO2only occurs when the supply of silicon to theSiO2/SixGe1−xinterface is insufficient. A comparison is made between simulation and experiment for wet oxidation (in pyrogenic steam) of polycrystallineSixGe1−xfilms. It is found that the model gives a good account of the oxidation process. Kinetic parameters, i.e., interfacial reaction rate constant for oxidation of germanium and diffusion coefficient of silicon (germanium) inSixGe1−x,are extracted by fitting the simulation to the experiment. ©1997 American Institute of Physics.