The dielectric breakdown mechanism in thin gate oxides is discussed based on the temperature dependence of hole fluence to dielectric breakdown through gate oxides. It has been demonstrated for the first time that the hole fluence to dielectric breakdown is not a constant value for different oxide fields but has a strong oxide field dependence at low temperatures. It has been also found that the dominant dielectric breakdown mechanism changes at around 150 K. At higher temperatures than 150 K, the dielectric breakdown mechanism in silicon‐dioxide is not dependent on the oxide field. On the other hand, the dielectric breakdown at lower than 150 K is dominated by the mechanism strongly dependent on the oxide field. ©1995 American Institute of Physics.