Abstract: An improved process of fabricating a shallow trench isolation structure is provided. A semiconductor substrate is provided and an insulating layer is formed over the substrate. A nitride masking layer is formed over the insulating layer. The nitride masking layer and the insulating layer are patterned and etched to expose a portion of the substrate, and to expose edges of the nitride masking layer and the insulating layer. The exposed portion of the substrate substantially defines boundaries of the isolation structure. A first oxide layer is deposited superjacent the exposed portion of the substrate, and over the nitride masking layer. A removing step includes removing portions of the first oxide layer lying over the nitride masking layer, a central portion of the first oxide layer superjacent the substrate, and a portion of the substrate to form a trench, leaving an oxide spacer disposed between the exposed edges of the nitride masking layer and the insulating layer, and the edge of the trench.