Breakdown character of thin SiO2 is investigated by using substrate hot-carrier injection techniques. Hot-carrier induced thin gate oxide damaged shows different breakdown character compared with the case of conventional F-N tunneling experiments.Good correlation between the calculated electron energy in the oxide and the electric field in the silicon substrate suggests that the difference between hot-electron injection and the F-N tunneling can be explained in terms of the average electron energy in the oxide.Hot holes injection experiments reveal that the life of oxide breakdown is not simply determined by the total number of injected holes.New hot-carrier-induced TDDB (Time-dependent dielectric breakdown)models of thin gate oxide are reported in this paper.