Metal‐nitride‐oxide‐silicon structures with various nitride thicknesses deposited on a 50–nm silicon dioxide layer prepared by a thermochemical reaction of tetraethylorthosilicate (TEOS) have been prepared. Capacitance‐voltage (C‐V) measurements have been performed after applying a voltage for a fixed time to determine the amount of accumulated interface charge. Infrared measurements have been carried out to obtain qualitative information about the internal stress in the TEOS layer. The accumulated charge and internal stress in TEOS increases with increasing nitride thickness. This observation indicates a lowering of the energy gap of TEOS.