Analyses of high‐TcNb3Ge films show that they all have a peak in oxygen concentration near the substrate‐film interface and that their lattice parameters in that region are abnormally large. It is proposed that high‐TcNb3Ge is a metastable phase which is formed via a homoepitaxial process from a large lattice parameterA15 Nb‐Ge phase. This phase near the interface is believed stable due to an expanded lattice resulting from the presence of impurities.