Abstract: A new method of local oxidation using an oxynitrided pad oxide layer to suppress the growth of a bird's beak is described. An oxide layer is provided over the surface of a semiconductor substrate. The oxide layer is annealed in a nitrogen atmosphere whereby the oxide layer is nitrided. The nitrided oxide layer is then reoxidized. A silicon nitride layer is deposited overlying the oxide layer. Portions of the silicon nitride and oxide layers not covered by a mask pattern are etched through to provide an opening exposing the portion of the semiconductor substrate that will form the field oxidation. The silicon substrate within the opening is oxidized wherein the semiconductor substrate is transformed to silicon dioxide wherein the nitrided oxide layer suppresses the formation of the bird's beak whereby the field oxidation is formed with a small bird's beak. The remaining oxide and silicon nitride layers are removed completing the field oxidation of the integrated circuit.