We compute the isotropic stress for a Ge film deposited on Si(0 0 1) and Si(1 1 1) at T = 870 K. By direct comparison with experimental phase diagrams measured for bulk Ge we deduce that Ge melts-at least partially-when deposited on Si surfaces at this temperature, due to the high heteroepitaxial stress (in the range 1-10 GPa), which has also been reported in experimental studies. Surface melting (complete or incomplete) induced by heteroepitaxial stress is consistent with a recent theoretical model proposed in the literature, and may account, at least in part, for the large values of Ge/Si intermixing reported in other studies. (C) 2002 Elsevier Science B.V. All tights reserved.