The work provides experimental results of high energy electron irradiation effects on silicon dioxide used for power MOS devices. A systematic increase of the threshold voltage has been observed in irradiated IGBT and VDMOS devices processed on Si〈100〉 and Si〈111〉, respectively. The threshold voltage shift has been interpreted as a result of the accumulated charge in the gate oxide. Single event gate rupture has been observed and attributed to the recoil ion interaction with the gate SiO 2 . The result has been corroborated by reliability stress tests. After electron irradiation, an increase in breakdown voltage appeared on all devices which was attributed to a change in the surface impact ionisation coefficient. The change is most notable in devices processed on Si substrate with 〈111〉 orientation.