Abstract Hot carrier degradation in asymmetric nDeMOS transistors is investigated in this paper. It is found that the worst case hot carrier stress condition in asymmetric nDeMOS transistors is at Ig,max, and not at Ib,max and hot-electron injection (HE, i.e. Vgs = Vds). Further, the damage regions in transistors upon various hot carrier stress modes are located by using variable amplitude charge pumping technique. It is found that the interface traps generation in the gate/n-type graded drain (NGRD) overlap and spacer/NGRD regions is the dominant mechanism of hot carrier degradation in transistors upon Ig,max stress mode. Moreover, both the interface trap generation and the electron trapping are two important factors to induce the electrical parameters shifts of asymmetric nDeMOS transistors under Ib,max and HE stress.