A method for forming patterns for semiconductor device includes following steps. A substrate is provided. The substrate includes a hard mask layer and a sacrificial layer formed thereon. A plurality of spacer patterns parallel with each other are formed on the substrate. A plurality of first blocking layers are formed in the sacrificial layer after forming the spacer patterns. A plurality of second blocking layers exposing at least a portion of the sacrificial layer and at least a portion the first blocking layer are formed on the substrate after forming the first blocking layer. Next, the sacrificial layer and the hard mask layer are etched with the spacer patterns, the first blocking layers and the second blocking layer being used as etching masks to form a patterned hard mask layer on the substrate.