To increase the rate of oxidation of Si in N2O, oxygen was added to N2O. The effect of varying the percentage of N2O in the total gas on the quality of the oxide was examined. It was experimentally determined that for a percentage of N2O more than about 50, the quality of the oxide is comparable to the oxide grown using pure N2O. This may suggest that to improve the quality of thermal oxide on Si (especially its hardness against hot carriers) a certain level of nitrogen atoms is sufficient. Increasing the nitrogen content of the oxide beyond that level does not further improve the oxide hardness and only results in smaller oxide growth rate.