In this paper, a detailed study of the superjunction MOSFET (SJ-MOSFET) thermal behavior on high-current conduction is presented. First, the heat-generation (HG) process and its dependence on device geometry and biasing conditions are elucidated from numerical-simulation tools. Later, the resultant temperature distribution is evaluated by simulation, thus, acquiring a physical understanding of its impact on the electrical characteristics and failure mechanisms, particularly at short-circuit operation. The obtained results show relevant differences with respect to the thermal behavior of conventional power MOSFETs. As a matter of fact, the maximum HG in SJ-MOSFET is found at a certain distance from the surface, which principally depends on the drift length. This fact has important implications on the device reliability prediction and a compact electrothermal modeling