One of the major components of a photoresist formulation is polymer resin. Well-defined diblock and random copolymer of tert-butyl acrylate (tBA) and 4-acetoxystyrene (StyOAc), as well as triblock and random tertpolymer of tBA, StyOAc, and Sty were prepared by reversible addition fragmentation chain transfer polymerization (RAFT) process. The polymers all possess M-s, about ten thousand and PDT less than 1.23. After hydrolysis under basic condition, the hydroxystyrene (StyOH) analogs are obtained and then are formulated as photoresist. Lithographic evaluation under KrF excimer laser shows that random copolymer based photoresist exhibits better S/L patterns according to SEM images. However, the lithographic performance of the terpolymer based resists is similar. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3245-3254, 2010