Litho-etch-litho-etch (LELE) is the double patterning (DP) technology of choice for 20 nm contact, via, and lower metal layers. We discuss the unique design and process characteristics of LELE DP, the challenges they present, and various solutions, including: • DP design methodologies, current DP conflict feedback mechanisms, and how they can help designers identify and resolve conflicts. • Effects on place and route (P&R) and new reqirements for physical design. • Why LELE DP cuts and overlaps are critical to optical process correction (OPC). • Mask misalignment and image rounding as new verification considerations.