A method for conducting sub-lithography feature patterning of a device structure is provided. First, a lithographically patterned mask layer that contains one or more mask openings of a diameter d is formed by lithography and etching over an upper surface of the device structure. Next, a layer of a self-assembling block copolymer is applied over the lithographically patterned mask layer and then annealed to form a single unit polymer block of a diameter w inside each of the mask openings, provided that w