PolymEric compound and resin composition for photoresist

A polymeric compound for photoresist, comprising a monomer unit represented by following Formula (I):

• and having a weight average molecular weight (Mw) of from about 5000 to about 50000;
• wherein the polymeric compound further comprises at least one monomer unit selected from Formulae (IIa) to (IIg):
• wherein R1 is a hydrogen atom or a methyl group;
• R2 and R3 are the same or different and are each a hydrocarbon group having from 1 to 8 carbon atoms;
• R4, R5 and R6 are the same or different and are each a hydrogen atom, a hydroxyl group or a methyl group;
• R7 and R8 are the same or different and are each a hydrogen atom, a hydroxyl group or a —COOR9 group, where R9 is a t-butyl group, a 2-tetrahydrofuranyl group, a 2-tetrahydropyranyl group or an 2-oxepanyl group;
• R10 and R11 are the same or different and are each a hydrogen atom, a hydroxyl group or an oxo group;
• R12 is a hydrocarbon group having a tertiary carbon atom at a bonding site with an oxygen atom indicated in the formula;
• R13, R14 and R15 are the same or different and are each hydrogen atom or a methyl group;
• R16 is a t-butyl group, a 2-tetrahydrofuranyl group, a 2-tetrahydropyranyl group or an 2-oxepanyl group;
• and n denotes an integer from 1 to 3;
• with the proviso that when the polymeric compound contains a monomer unit of Formulae (IIg), the polymeric compound further comprises at least one of Formulae (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (IIIa), (IIIb), (IIIc), (IIId), (IIIe), (IIIf) and (IIIg)
• wherein Formulae (IIIa) to (IIIg) have the following formulae:
• wherein R1 is a hydrogen atom or a methyl group;
• R17 and R18 are the same or different and are each a hydrogen atom, a hydroxyl group or a carboxyl group;
• R19 is a hydroxyl group, an oxo group or a carboxyl group;
• R20, R21, R22, R23 and R24 are the same or different and are each a hydrogen atom or a methyl group;
• R25 is a hydrogen atom or a methyl group;
• R26 is a tricyclo[5.2.1.02,6]decylmethyl group, a tetracyclo[4.4.0.12,5.17,10]dodecylmethyl group, a norbornyl group, an isobornyl group or a 2-norbornylmethyl group;
• and R27 is a substituent of R26 and is a hydrogen atom, a hydroxyl group, a hydroxymethyl group, a carboxyl group or a —COOR28 group, where R28 is a t-butyl group, a 2-tetrahydrofuranyl group, a 2-tetrahydropyranyl group or an 2-oxepanyl group.