In this study we report a systematic investigation of the metastable morphologies of Si1-xGex layers obtained by the interplay of kinetics and thermodynamics during growth on Si(001). We show that three main growth regimes can be distinguished as a function of the misfit and of the deposited thickness. They correspond to three equilibrium steady state morphologies that consist of(105)-facetted hut islands, huts and domes in co-existence, and a bimodal size distribution of domes, respectively. The shape transitions between these states are attributed to different levels of relaxation.