Silicon-containing resist underlayer film forming composition having fluorine-based additive

A resist underlayer film forming composition for lithography includes: as a component (I), a fluorine-containing highly branched polymer obtained by polymerizing a monomer A having two or more radical polymerizable double bonds in the molecule thereof, a monomer B having a fluoroalkyl group and at least one radical polymerizable double bond in the molecule thereof, and a monomer D having a silicon atom-containing organic group and at least one radical polymerizable double bond in the molecule thereof, in the presence of a polymerization initiator C in a content of 5% by mole or more and 200% by mole or less, based on the total mole of the monomer A, the monomer B, and the monomer D; and as a component (II), a hydrolyzable silane compound, a hydrolysis product thereof, a hydrolysis-condensation product thereof, or a silicon-containing compound that is a combination of these compounds.