Resist underlayer film forming composition containing polymer having nitrogen-containing silyl group

A resist underlayer film foaming composition for lithography comprising:

• a polymer containing a partial structure of Formula (1):
• [where
• X1 is a group of Formula (2), Formula (3), Formula (4) or Formula (4-1):
• R0 is a hydrogen atom, an alkyl group, an aryl group or an alkenyl group,
• R1s are independently a divalent organic group,
• R2s are independently an organic group bonded to a silicon atom through a Si—C bond and having an alkyl group, an aryl group, a halogenated alkyl group, a halogenated aryl group, an alkenyl group, an epoxy group, an acryloyl group, a methacryloyl group, a mercapto group, an amino group or a cyano group,
• O— is a group bonded to a silicon atom through a Si—O bond,
• R3 and R4 are independently a hydrogen atom, a C1-10 alkyl group, a C3-6 alkenyl group, a benzyl group or a phenyl group (where, the phenyl group is optionally substituted with a group selected from a group consisting of a C1-10 alkyl group, a halogen atom, a C1-10 alkoxy group, a nitro group, a cyano group, a hydroxy group and a C1-10 alkylthio group), or
• R3 and R4 form together with a carbon atom to which R3 and R4 are bonded, a C3-6 ring, and
• n, m and p are independently an integer of 0 to 3,
• with the proviso that when X1 is a group of Formula (2), Formula (3) or Formula (4-1), 0≦n+m≦5 is satisfied, and
• when X1 is a group of Formula (4), 0≦n+m+p≦8 is satisfied];
• and
• a solvent.