This article presents a thermal behaviour study of IGBT (insulated gate bipolar transistors). The authors have particularly studied the stored charge variation in IGBT structures when the temperature increases in connection with the device technology. The first section presents experimental measurements revealing a different thermal behaviour between the two main technologies : punch-through (PT) and nonpunch-through (NPT) IGBT. The authors identify these two technologies using reverse engineering techniques to point out the particular points which could explain the thermal behaviour difference. This part allows the extraction of technological parameters which are necessary to simulate the electrical behaviour with a 2-dimensional device simulator. A simple static model including technology particularities is then presented. This simple model helps find the physical origin of the two thermal behaviours. In conclusion, the authors summarize the two kinds of electrical temperature sensitivities in connection with IGBT technology.