Modified locus isolation process in which surface topology of the locos oxide is smoothed

A method for fabricating semiconductor devices having field oxide isolation structures comprising:

• providing a silicon substrate;
• forming a multilayer oxidation masking structure having a first silicon oxide layer and a silicon nitride layer;
• forming a mask by removing said silicon nitride layer and said first silicon oxide layer over regions where said field oxide isolation structures are to be formed;
• oxidizing said regions to form said field oxide isolation structures;
• removing resulting remaining portions of the silicon nitride layer with aqueous chemical etchants;
• depositing a second silicon oxide layer over said silicon substrate;
• anisotropically etching said second silicon oxide layer using a method of end-point-detection to terminate the anisotropic etching of said second silicon oxide layer upon exposure of the silicon substrate, taking care not to remove resultant remaining portions of said second silicon oxide layer which lie adjacent to topological contours;
• and
• forming semiconducting devices within the re-exposed silicon regions.