The radiation hardness of metal‐oxide semiconductor capacitors with nitrided oxides prepared by rapid thermal nitridation (RTN) has been studied. The radiation was performed by exposing devices to 50 keV x ray to a dose of 0.5 Mrad (Si). Compared to conventional thermal oxides, the rapid thermal nitrided oxide devices exhibit much less increase in the interface state density (Dit). In addition, it is found that higher RTN temperatures and/or longer durations produce smaller &Dgr;Dit. The significant reduction of the interface state generation has been attributed to the strain relief effect due to the incorporation of nitrogen at the Si/SixNyOzinterface. The bond strain related models have been discussed to explain the results.