Abstract : As Silicon limits are reached, Ge-based materials are expected to be progressively introduced in the fabrication of advanced microelectronic devices. SiGe layers are already used as Source/Drain regions to induce uniaxial compressive stress in the Si channel, which results in the enhancement of hole mobility in PMOS. In this work, we study an alternative method for the fabrication of shallow SiGe regions, in which a pure Ge layer is deposited on a Si substrate and the Ge in-diffusion is induced by a subsequent anneal. The optimisation of such a technology requires the accurate measurement of the Ge concentration in the full range of Ge composition and the understanding of the Si-Ge interdiffusion occurring during the formation of the SiGe layers. Pure Ge(:B) layers were grown on Si substrates by CVD. We present a novel SIMS MCs2+ methodology for the accurate measurement of the Ge diffused profiles. Boltzmann-Matano analysis was used to extract the interdiffusion coefficients. Si-Ge interdiffusion is found to be strongly dependent on the Ge concentration. Also, an effect of dislocations near the Ge/Si original interface is suggested by our results. A physical model including the various observed effects is proposed, that gives a very good agreement with experiments. We also show that the effect of the in-situ B doping of the pure Ge layer is to reduce the interdiffusion. Finally, we suggest that the use of polycristalline Ge films is a promising route for the formation of gradual Si1-xGex layers.