Patent ID: 7064072

Claim:
A method for fabricating trench isolation, comprising: providing a semiconductor substrate having a front surface and a backside; forming a first silicon oxide layer on the front surface of the semiconductor substrate and, simultaneously, forming a second silicon oxide layer on the backside of the semiconductor substrate; forming a first silicon nitride layer on the front surface of the semiconductor substrate and, simultaneously, forming a second silicon nitride layer on the backside of the semiconductor substrate; performing lithographic and etching process and using the first silicon nitride layer as an etching hard mask to etch a trench into the front surface of the semiconductor substrate; filling the trench with insulating material, the insulating material also covering the first silicon nitride layer; using the insulating material as an etching hard mask and etching away the second silicon nitride layer on the backside of the semiconductor substrate; performing a densification process to densify the insulating material; and performing a chemical mechanical polishing process and using the first silicon nitride layer as a polish stop to planarize the insulating material.