Surface nitridation of thin SiO2films (130 A˚) has been achieved in low ammonia pressures (P≤10−1mbar) by thermal activation (900 °C≤T≤1050 °C) or by electron‐beam‐enhanced reaction at room temperature. In the first case, the nitridation rate increases withP,T, and timet; in the latter, it depends onP,t, electron energy and flux, and reaches a maximum within the energy range (1–∼1.7 keV). Electrical characterization of metal‐insulator‐semiconductor structures shows that the SiO2/Si interfacial quality is not damaged as long as interfacial nitrogen concentration remains negligible. However, bulk and/or interfacial fixed positive charges are detected in the SiO2films nitrided at room temperature.