Patent ID: 7915137

Claim:
A method of forming an isolation structure in a semiconductor substrate comprising: depositing a first mask layer on the substrate; depositing a second mask layer on the first mask layer; patterning the second mask layer to form a first opening in the second mask layer; etching the first mask layer through the first opening to form a second opening in the first mask layer; implanting a first dopant of a first conductivity type through the second opening to form a first region of the first conductivity type under the second opening; removing the second mask layer; heating the substrate so as to form a first field oxide region in the second opening of the first mask layer; forming a trench in the substrate; depositing a first dielectric material in the trench; removing a portion of the first dielectric material such that a surface of the first dielectric material is located at a first level below a second level of a surface of the substrate, thereby forming a first recess over a remaining portion of the first dielectric material; removing a portion of the first field oxide region such that a surface of the first field oxide region is located at a third level below the second level, thereby forming a second recess over a remaining portion of the first field oxide region; depositing a second dielectric material in the recesses; and removing portions of the second dielectric material such that the entire surface of the second dielectric material in each of the first and second recesses is substantially coplanar with a surface of the substrate.