Shallow trench isolation formation with simplified reverse planarization mask

摘要

An insulated trench isolation structure with large and small trenches of differing widths is formed in a semiconductor substrate using a simplified reverse source/drain planarization mask. Embodiments include forming trenches and refilling them with an insulating material which also covers the substrate surface, polishing to remove an upper portion of the insulating material and to planarize the insulating material above the small trenches, depositing a second, thin layer of insulating material filling seams in the insulating material above the small trenches, masking the insulating material above the large trenches, isotropically etching, and polishing to planarize the insulating material. Since the insulating material is partially planarized and the seams over the small trenches are filled, etching can be carried out after the formation of a relatively simple planarization mask over only the large trenches, and not the small trenches. The use of a planarization mask having relatively few features with relatively large geometry avoids the necessity of creating and implementing a complex, critical mask, thereby reducing manufacturing costs and increasing production throughput.