Abstract This work shows an experimental study on the reliability of PowerMOSFET devices used in satellitar application. The total irradiated dose (TID) tolerance degree of a gate oxide as a function of its thickness and growth process has been investigated. Different oxide thin films, with thickness ranging from 25 nm to 35 nm, integrated in 30 V and 100 V N-channel STM PowerMOSFET vehicles, have been examined. The gate threshold voltage has been used to evaluate the degradation, in comparison to a predictive model. The attention is stressed onto non-ideality factors involving the gate degradation.