The charging and discharging properties of electron traps created by hot‐carrier injections in the thin gate oxide of n‐channel metal oxide semiconductor transistors are analyzed by means of the effects that charge state transitions induce on the low‐level gate current (lower than 1 pA) of the transistor. This current is measured by a very senstive floating‐gate technique [F.H. Gaensslen and J.M. Aitken, IEEE Electron. Device Lett. EDL‐1, 231 (1980)]. Two traps with electron capture cross sections of the order of 1E-14 and 1E-15 cm2 are analyzed which are linked with optical and field‐dependent measurements of electron emission properties. Thermal and optical ionization energies of these defects are determined at ≊1.7±0.2 and ≊3.0±0.5 eV, respectively. Comparison with theory suggests that Si dangling bonds or oxygen vacancy in the oxide should be the defects created by hot‐carrier injections.