Ge2Sb2Te5 is a phase change material candidate to constitute the active element of future nonvolatile memory devices. The evolution of the thermal resistance at the interface between an aluminum thin layer and Ge2Sb2Te5 is studied using the time resolved pump probe technique from room temperature to 400 °C. The thermal resistance is influenced by the amorphous to crystalline phase change occurring in Ge2Sb2Te5. The decrease in the thermal resistance from the amorphous to the crystalline phase is well explained by the diffuse mismatch model asymptotic form for high temperature. The large increase of the interface thermal resistance between fcc and hcp crystalline states is explained by the fast and significant grain growth and species inter-diffusion during this second phase change. This leads to the formation of an interfacial layer whose chemical and mechanical intrinsic properties have been …