We present that an interference lithography technique beyond the diffraction limit can be theoretically achieved by positing an anisotropic metamaterial under the conventional lithographic mask. Based on the special dispersion characteristics of the metamaterial, only the enhanced evanescent waves with high spatial frequencies can transmit through the metamaterial and contribute to the lithography process. Rigorous coupled wave analysis shows that with 442nm exposure light, one-dimensional periodical structures with 40nm features can be patterned. This technique provides an alternative method to fabricate large-area nanostructures. (c) 2008 Optical Society of America.