To provide a composition for gap formation capable of forming sacrifice areas made of a sacrificial material decomposable completely into vapor at a desired temperature, and also to provide a semiconductor device-manufacturing method using the composition.Disclosed is a composition for gap formation comprising a polymer and a solvent:wherein said polymer comprising five or more of repeating units which are represented by at least one kind of the following formula (1) or (2): Ar1-L1  (1) Ar2-L2-Ar2′  (2) [each of Ar1, Ar2 and Ar2′ is independently a substituted or unsubstituted aromatic group; and each of L1 and L2 is independently oxygen, sulfur, alkyl, sulfone, amide, ketone or a group represented by the following formula (3): {Ar3 is an aromatic group; and L3 is a trivalent atom selected from the group consisting of nitrogen, boron and phosphorus}].