Charge defects in metal oxide semiconductor capacitors formed with N2O oxynitrides are analyzed by Fowler-Nordheim tunneling injection stress. These oxides are found to incur fewer interface states and lower flatband voltage shifts, the higher the oxynitridation temperature, between 850 and 1050 degrees C. Analysis of oxide traps during constant-current Fowler-Nordheim stress uncovers complex phenomena in oxide trap creation. Several features of the data indicate an optimum at an oxynitridation temperature of 850 to 950 degrees C, including initial net-positive oxide trap creation, and changes in rates of oxide trap creation. However, the net-negative oxide trapping at high cumulative injected charge simply decreases with higher oxynitridation temperatures. There is evidence that "slow" donor states (or anomalous positive charge) near the Si/SiO2 interface may be suppressed by this oxide process.