Chemically amplified positive resist composition and patterning process

A chemically amplified positive resist composition comprising (A) an organic solvent, (B) a base resin, and (C) an acid generator,

• said base resin (B) comprising a first polymer comprising recurring units represented by the general formula (1) and having a weight average molecular weight of 1,000 to 500,000, and a second polymer comprising recurring units of acrylate or methacrylate represented by the general formula (2) and having a weight average molecular weight of 1,000 to 500,000,
• wherein R1 is hydrogen, hydroxyl, straight alkyl, branched alkyl, halogen or trifluoromethyl, R2 is hydrogen, hydroxyl, halogen or trifluoromethyl, R3 is C4-C12 tertiary alkyl, R4 is hydrogen, an optionally substituted alkyl group, optionally substituted alkoxy group, —C(CF3)2—OH, trialkylsiloxy group in which each alkyl moiety has 1 to 6 carbon atoms, C4-C20 oxoalkoxy group, tetrahydropyranyloxy group, tetrahydrofuranyloxy group, or trialkylsiloxy group, R5 is hydrogen or methyl, R6 is hydrogen, methyl, alkoxycarbonyl, cyano, halogen or trifluoromethyl, R7 is C4-C30 alkyl, n is 0 or a positive integer of 1 to 4, m is 0 or a positive integer of 1 to 5, p and r each are 0 or a positive number, s is a positive number, q is a positive number, and p+q+r+s=1,
• wherein R8 is hydrogen or methyl, and R9 is selected from the group consisting of a straight, branched or cyclic C2-C24 alkyl group, a C2-C12 alkoxyalkyl group, a C1-C12 hydroxyalkyl group, an organic group of the formula (3):
• —(RO)n—R′ (3)
• wherein R is C2-C4 alkylene, R′ is C1-C6 alkyl, and n is an integer of 1 to 6, and an organic group of the formula (4):
• wherein R″ is a straight, branched or cyclic C1-C12 alkyl group, a C2-C12 alkoxyalkyl group, a C1-C12 hydroxyalkyl group, or a C3-C12 (poly)alkylene glycol alkyl group.