Patent ID: 8609543

Claim:
A method for fabricating a semiconductor device, the method comprising: providing a substrate having a first region and a second region; forming an etch target layer over the first and the second regions of the substrate simultaneously; forming a hard mask layer over the etch target layer to have different thicknesses over the first and the second regions, wherein the hard mask layer is composed of at least three or more layers and at least one set of the top two layers is composed of the same material; forming a hard mask pattern by etching the hard mask layer; and simultaneously etching the etch target layer over the first and the second regions using the hard mask pattern as an etch mask to form a target pattern having different densities over the first and the second regions, wherein the hard mask layer has a greater thickness over the first region than over the second region, wherein the first region is a cell region and the second region is a peripheral region, wherein the cell region has a higher pattern density compared to the peripheral region.