Methods of forming field oxide and active area regions on a semiconductor substrate

Abstract

Methods of forming a field oxide region and an adjacent active area region are described. A semiconductive substrate is masked with an oxidation mask while an adjacent area of the substrate remains unmasked. The substrate is exposed to conditions effective to form a field oxide region in the adjacent area. The field oxide region has a bird's beak region which extends toward the active area. A mass of material is formed over at least a portion of the bird's beak region. In a preferred implementation, the mass of material is formed from material which is different than the material from which the oxidation mask and the field oxide region are formed. According to one aspect of the invention, the material comprises, polysilicon. In another preferred implementation, such different material comprises a spacer which is formed over at least a portion of the oxidation mask. Preferably, an undercut region is formed under the mass or spacer and subsequently filled with oxide material. During the filling of the undercut region, at least some of the mass or spacer is oxidized to form a bump over the bird's beak region. Oxide material is then removed from over the active area with such removal reducing the size of the bump. A gate dielectric layer can then be provided over the active area.