The materials‐related effects due to rapid thermal nitridation and reoxidation of thermally grown SiO2were studied in the underlying silicon. Depth profiles using spreading resistance, auger electron spectroscopy, and secondary‐ion mass spectroscopy are presented to show that enhanced dopant diffusion and surface depletion result from rapid thermal process treatments. Silicon interstitial injection from the nitrogen supersaturated oxynitride interface facilitates the diffusion of boron, phosphorus, and arsenic atoms in the silicon substrate. An appreciable amount of nitrogen was found below the silicon surface, suggesting that nitrogen interstitials may play an important role in the observed enhanced impurity diffusion.