Provided is a composition for forming a
resist underlayer film, which satisfies various other characteristics such as curability, the amount of sublimate generated, planarization, and optical characteristics (reflection suppression during
exposure) in addition to
etching resistance and
heat resistance. A composition for forming a
resist underlayer film, the composition containing a novolac resin and a
solvent, the novolac resin containing a
structural unit (A) having an aromatic ring, the
structural unit (A) including one or more structural units represented by formula (A), R1 being a
hydrogen atom or a specific
substituent, R2 being an optional specific
substituent, and R3 being a
hydrogen atom or a specific
substituent. In the novolac resin, at least some of R1 and R2 are substituents having an alkynyl chain having 2-10 carbon atoms, n represents the number of substituents R2, when there are a plurality of n, the plurality of R2 may be the same as or different from each other, and * represents a linking bond. # imgabs0 #