Patent ID: 6995095

Claim:
A method for forming shallow trench isolation structures, the method comprising: providing a substrate having a cell region and a periphery region; forming a hard mask upon the substrate so as to cover at least a portion of the cell region and at least a portion of the periphery region; forming a patterned photoresist layer upon the hard mask, the photoresist layer exposing a portion of the hard mask in the cell region and exposing a portion of the hard mask in the periphery region; performing a first etching process to remove substantially all of the hard mask layer exposed by the photoresist layer in the periphery region and to remove a portion of the hard mask layer exposed by the photoresist layer in the cell region; performing a second etching process to partially form a trench in the periphery region and to remove more of the hard mask layer in the cell region; performing a third etching process to deepen the trench formed in the periphery region and to form a trench in the cell region; and filling the trench in the periphery region and filling the trench in the cell region with an insulating material.