| abstract |
A method of forming a semiconductor device comprises the steps of forming a patterned pad oxide layer having a first nitrogen concentration over a semiconductor substrate assembly such as a semiconductor substrate. The substrate is oxidized to form field oxide which also forms an area of Kooi nitride at the interface of the field oxide and the active area. The Kooi nitride comprises a second nitrogen concentration which is less than the nitrogen concentration of the pad oxide. Next, the pad oxide and the Kooi nitride are oxidized thereby forming gate oxide over the pad oxide. The nitridized pad oxide oxidizes slower than the Kooi nitride, and therefore gate oxide thinning which is known to result from Kooi nitride is reduced or eliminated. Further, the need for the growth of a sacrificial oxide layer to remove the Kooi nitride, and a subsequent strip of the sacrificial oxide is eliminated thereby reducing thinning of the field oxide. |