Patent ID: 6900090

Claim:
A method for forming a trench isolation comprising the steps of: forming a planarization stop layer on a semiconductor substrate on which a pad oxide layer is formed; forming a trench in the semiconductor substrate by etching sequentially a part of the planarization stop layer, a part of the pad oxide film, and a part of the semiconductor substrate; performing a thermal oxidation process to form a thermal oxide film on bottom and sidewall surfaces of the trench and on a sidewall and a top surface of the planarization stop film; filling the trench with a trench fill insulating material in which the thermal oxidation process is performed; planarizing the trench fill insulating material such that the planarization stop layer is exposed; recessing the trench fill insulating material to under the planarization stop film; and forming a trench oxidation-preventive film on the recessed trench fill insulating material.