A simple and novel method was developed to fabricate a nanoporous template by using a bilayer system composed of a silicon-containing block copolymer top layer and a dually responsive photoresist bottom layer. The dually responsive bottom layer became cross-linked by heating. The cross-linked polymer was mechanically hard and insoluble in common solvents. The block copolymer pattern was transferred to the bottom layer by oxygen reactive ion etching. High-aspect-ratio nanopore arrays were generated. The cross-linked bottom layer became soluble again by chain scission upon exposure to UV light. Therefore, the template with a highly orientated array of cylindrical nanopores could be easily removed by dipping in an aqueous base solution. This versatile template of nanoporous structures could be used to create freestanding 1D nanostructures of a variety of functional materials.