Results are presented of a detailed study of the effects of a high-temperature 2-MeV electron irradiation on the performance degradation of STI (shallow trench isolation) diodes. Reverse current increases after irradiation. After 20 °C irradiation, two majority hole capture levels with (Ev+0.18 eV) and (Ev+0.34 eV) were induced. The degradation of the device performance and the introduction rate of the lattice defects decrease with increasing irradiation temperature. This result suggests that the creation and recovery of the radiation damage proceeds simultaneously at high temperature.