US Patent 9911646 Self-aligned double spacer patterning process

Embodiments of the present disclosure are a method of forming a semiconductor device and methods of patterning a semiconductor device. An embodiment is a method of forming a semiconductor device, the method including forming a first hard mask layer over a semiconductor device layer, forming a set of mandrels over the first hard mask layer, and forming a first spacer layer over the set of mandrels and the first hard mask layer. The method further includes forming a second spacer layer over the first spacer layer, patterning the first spacer layer and the second spacer layer to form a mask pattern, and patterning the first hard mask layer using the mask pattern as a mask.