The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradations on irradiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation (STI). The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.