The mechanism of direct tunneling (DT) for electron emission from the n-type Si substrates to the thin SiO2 film is examined analytically using the Wentzel, Kramers, Brillouin method with a consideration of the Fermi-Dirac distribution function for electrons at room temperature. The calculated DT currents reproduced the measured data more precisely than those without a consideration of the distribution function at room temperature particularly in the low voltages. (C) 2002 Elsevier Science Ltd. All rights reserved.