A gate structure for an ONO flash memory device includes a first layer of silicon oxide on top of a semiconductor substrate, a second layer of silicon oxide, a layer of silicon nitride sandwiched between the two silicon oxide layers, and a control gate on top of the second layer of silicon oxide. Nitrogen is implanted into the first layer of silicon oxide and then the semiconductor structure is heated using a rapid thermal tool to anneal out the implant damage and to diffuse the implanted nitrogen to the substrate and silicon oxide interface to cause SiN bonds to be formed at that interface. The SiN bonds are desirable because they improve the bonding strength at the interface and the nitrogen remaining in the silicon oxide layer increases the oxide bulk reliability.