The dependencies of MeV He single-ion-induced interface traps on oxide thickness and oxide electric fields Eox during irradiation was investigated quantitatively with a single-ion microprobe. Under a negative electric field, the number of interface traps induced by a single ion becomes constant at about 0.1 regardless of both the oxide thickness and oxide electric field. Under a positive electric field, the generation rate of interface traps per ion for thicker oxide metal–oxide–semiconductor field-effect transistors (MOSFETs) is greater than that for thinner oxide MOSFETs. We also found that the generation rates increase with dependence on the oxide electric field of Eox0.2, regardless of the oxide thicknesses. The field dependence of interface traps under a positive electric field was found to be very similar to that of oxide trapped holes. The causes of this dependence are discussed comprehensibly. © 1999 American Institute of Physics.