Defect-free and dense micropillar arrays with a high aspect ratio are replicated from etched Si masters using high-modulus polyurethane acrylate. The newly designed conformable solid-index mask can generate high-resolution 3D nanostructures that can be patterned through proximity field nanopatterning (PnP) in a single exposure step. The superb optical property proves the quality of 3D nanostructures.