The subthreshold characteristics ofn‐channel metal‐oxide‐semiconductor field effect transistors after high‐field, high current density (100 mA/cm2) Fowler–Nordheim electron injection are investigated. Rapid changes are observed and recorded within 1000 s after injection. A ‘‘bump’’ in the subthresholdI‐Vcharacteristic appears if electron trapping in the gate oxide dominates. This bump can be made to disappear and reappear by controlling the amount of trapped electrons in the oxide. This may be readily explained by the parasitic channel leakage current along the isolation field oxide edges.