The incorporation of oxygen into a silicon substrate was investigated during the growth of Al2O3 gate oxide. Al2O3 films were grown on p-type (100) silicon wafers, at 100 degrees C, using plasma enhanced atomic layer deposition. Methylpyrrolidine alane (C5H14NAl) and capacitively coupled O-2 plasma were used as the sources of Al and O, respectively. The interstitial oxygen in the silicon substrate was found by Fourier transform infrared spectroscopy, and the amount of interstitial oxygen found increased when the thickness of Al2O3 was increased. This phenomenon was attributed to the diffusion of oxygen atoms throughout the Al2O3 layer. (c) 2005 The Electrochemical Society.