There is provided a gap fill material forming composition for lithography that is used in dual damascene process and contributes toward an improvement in production efficiency. Concretely, it is a gap fill material forming composition characterized in that the composition is used in manufacture of semiconductor device by a method comprising coating a photoresist on a substrate having a hole with aspect ratio shown in height/diameter of 1 or more, and transferring an image to the substrate by use of lithography process, and that the composition is coated on the substrate prior to coating of the photoresist, and comprises a polymer having a hydroxy group or a carboxy group and a crosslinking agent. The gap fill material layer obtained from the gap fill material forming composition can be etched back with an alkaline aqueous solution.