A quantum mechanical analysis of the gate current and trapped charge inside oxide layer of an enhancement type MOSFET has been presented in this paper. The effects of the impurity atoms inside oxide layer on the gate current and trapped charge have been analyzed. Carrier trapping due to an impurity atom inside the oxide layer is simulated using a rectangular potential well. Calculation of the gate current and trapped charge is carried out for various MOSFET parameters. (C) 2002 Elsevier Science Ltd. All rights reserved.