The amorphous (a) to microcrystalline (&mgr;c) transition, induced by the increase of the ion bombardment energyEionand the substrate temperatureTs, is investigated on glow‐discharge deposited germanium thin films. This transition and the deposition of &mgr;c‐Ge on metallic substrates are observedinsituby kinetic and spectroscopic phase modulated ellipsometry (SPME) over the range 1.7–4.5 eV. The ion bombardment energy corresponding to the transitiona‐&mgr;c (Eion∼120 eV) decreases as a function ofTsin the range 160–280 °C. DecreasingEion(orTs) results in the reverse transition. The &mgr;c‐atransition is found at a ∼50 eV (or ∼120 °C) lower value, giving evidence of an epitaxial growth effect. The kinetics of the growth processes is deduced from the SPME data by using an effective medium approximation. The early stage of the growth is accurately described by the nucleation of microcrystalline islands at a 50 A˚ level; the time dependence being coherent with a low surface mobility of the diffusing species. During the growth, a composition depth profile is observed; the ∼150 A˚ thick surface layer being more amorphous than the bulk.