A low-energy (550 eV) argon-ion beam was used to directly bombard the backsurface of nitrided n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) after the completion of all conventional processing steps. The interface and oxide-charge trapping characteristics of the bombarded MOSFETs were investigated as compared to nonbombarded and reoxidized-nitrided n-MOSFETs. It was found that after bombardment, interface state density decreases and interface hardness against hot-carrier bombardment enhances, and oxide charge trapping properties were also improved. The improvements exhibit a turnaround behavior depending on bombardment conditions and could be attributed to stress compensation in the vicinity of the Si/SiO2 interface and an annealing effect. © 1997 American Institute of Physics.