Resist underlayer film-forming composition

A method for producing a patterned substrate, the method comprising

• a step of forming a resist underlayer film on a substrate by use of a resist underlayer film-forming composition;
• a step of forming a specific hard mask on the resist underlayer film;
• a step of forming a photoresist film on the hard mask;
• a step of forming a resist pattern through light exposure to and development of the photoresist film;
• a step of mask-patterning by etching the hard mask through the resist pattern;
• a step of forming a resist underlayer pattern by etching the resist underlayer film through the mask pattern;
• and
• a step of processing the substrate through the resist underlayer pattern;
• wherein
• the resist underlayer film-forming composition contains a polymer that is a novolak resin having a structure in which an addition unit having a group represented by the following formula (1) is bound to any of the rings of a formed novolak resin:
• wherein
• each Rx, Sy, and Sz represents a hydrogen atom or a monovalent organic group that has 2 to 20 carbon atoms and optionally includes at least one of a nitrogen atom, an oxygen atom, and a sulfur atom, and comprises a cyclic skeleton having from 2 to 5 and 7 to 20 carbon atoms, a linear-chain skeleton, or a branched-chain skeleton;
• each Ry and Rz represents a single bond or a divalent organic group;
• each of ring Ary and ring Arz represents a C4 to C20 cyclic alkyl group or a C6 to C30 aryl group, and ring Ary and ring Arz may be linked together to form a new ring structure therebetween;
• ny is an integer of 0 to the maximum number corresponding to allowable substitution to ring Ary;
• nz is an integer of 0 to the maximum number corresponding to allowable substitution to ring Arz;
• and
• * is a novolak resin bonding site.