Abstract : Strong demand for robustness has emerged in all areas of application of power components. Only a detailed analysis of phenomena related directly or indirectly to failures can ensure the reliability of the functions of the new power components. However, these phenomena involve the coupling between electrical, thermal and mechanical effects, making their study very complex, therefore the use of multi-physics modeling is well suited. In this thesis, we propose a methodology for electrical modeling taking into account the effects of temperature on the localized phenomena that initiate failure is often fatal. In preparation for the coupled electro-thermal simulation involving MOS power transistors, an electric thermo-sensitive model of the MOS and its body diode has been developed. Correspondingly a set of experimental studies was implemented to extract the parameters and model validation. Particular attention was paid to the study of interference phenomena that could occur in a localized response to an inhomogeneous distribution of temperature and hot spots. Thus the workings limits avalanche, with the outbreak of parasitic bipolar transistor (snapback) and its reversal were modeled. Benches specific validations of the model for harsh switching conditions were used by taking precautions related to high temperature. Finally, the complete thermal electric model developed was used by the company "EPSILON Ingénierie" for electro-thermal simulation of power MOS mode Avalanche Software adapting Epsilon-R3D.