A method for manufacturing a semiconductor device includes forming a hard mask layer overlying a device layer of a semiconductor device, a mandrel underlayer over hard mask layer, and a mandrel layer over mandrel underlayer. The mandrel layer has a plurality of mandrel lines extending along a first direction. A plurality of openings are formed in mandrel underlayer extending in a second direction substantially perpendicular to first direction. A spacer layer is formed over mandrel underlayer and layer. Spacer layer fills plurality of openings in underlayer. Portions of spacer layer are removed to expose an upper surface of underlayer and mandrel layer, and mandrel layer is removed. By using remaining portions of spacer layer as a mask, underlayer and hard mask layer are removed, to form a hard mask pattern with first hard mask pattern lines extending along first direction and second hard mask pattern lines extending along second direction.