Bottom resist layer composition and patterning process using the same

A bottom resist layer composition for a multilayer-resist film used in lithography which comprises, at least, a polymer having a repeating unit represented by the following general formula (1),

• ,wherein R1 represents any one of a hydrogen atom, a linear, branched or cyclic alkyl group having 1-10 carbon atoms, an aryl group having 6-10 carbon atoms, a linear, branched or cyclic alkenyl group having 2-10 carbon atoms, and a halogen atom, R2 and R12 independently represent any one of a hydrogen atom, a linear, branched or cyclic alkyl group having 1-6 carbon atoms, a linear, branched or cyclic alkenyl group having 2-6 carbon atoms, an aryl group having 6-10 carbon atoms, an acyl group or an alkoxy carbonyl group having 1-10 carbon atoms, a group forming an acetal group with an oxygen atom bonded with R2 or R12 in the above general formula (1), and a glycidyl group, R3 and R13 independently represent any one of a hydrogen atom, a linear, branched or cyclic alkyl group having 1-10 carbon atoms, and an aryl group having 6-10 carbon atoms, a and b satisfy 0<a<1, 0<b<1, and 0<a+b≦1, and Z represents fused polycyclichydrocarbon which may have hetero atoms.