A strong demand of even more compact and reliable devices has powered in the last years the development of advanced power MOSFET structures. Among them, the planar STripFET™ has been introduced as an alternative to conventional trench gate MOSFET in low voltage (<60 V) applications. Moreover low voltage Super-Junction devices are also under development. In this paper a conventional trench gate MOSFET is compared in terms of reliability with a STripFET™ and a Super-Junction device. The comparison is accomplished through a reliability model taking advantage from a dynamic analysis of the temperature distribution over the metal source surface in an effort to correlate electric working conditions to thermo-mechanical stresses.