The time dependence of changes in the oxide trapped charge during interface trap formation is investigated. Changes in MOSFET threshold voltage V/sub th/ and number of interface traps N/sub it/ are measured in the same sample as a function of time following pulsed irradiation. When the gate bias during irradiation V/sub gl/ is positive, the initial mod Delta V/sub th/ mod is large due to trapping of radiation-induced holes at the Si-SiO/sub 2/ interface and the postirradiation time dependence of Delta V/sub th/ is dominated by hole detrapping, as expected. When V/sub gl/ is negative, interfacial hole trapping is minimized. In this case, an unusual peak in the Delta V/sub th/ vs. time curve provides evidence of the involvement of H/sup +/ ions in the N/sub it/ formation process. >