The invention is directed to a method for patterning a material layer. The method comprises steps of forming a mask layer on the material layer. A multiple patterning process is performed on the mask layer for transferring at least a first pattern from a first photomask through a first photoresist and a second pattern from a second photomask from a second photoresist layer into the mask layer without performing any etching process. The mask layer exposes a portion of the material layer and the mask layer is patterned at the time that the first photoresist layer and the second photoresist layer are developed respectively. An etching process is performed to pattern the material layer by using the mask layer as an etching mask.