Various derivatives of modified poly(4-hydoxystyrene-co-4-(1-ethylethoxystyrene))(M-EEPHS) were synthesized by insertion of third monomer unit such as styrene, 4-acetoxystyrene, 4-methoxycarbonyloxystyrene, tertbutoxycarbonyloxystyrene, tert-butyl acrylate, and 4-(1-cyclohexylethoxy)styrene. Their dissolution rate behavior was investigated with different blocking level. From the average dissolution rate of M-EEPHS in a 2.38wt% TMAH solution as a function of the total protection%, hydrophobicity was proven as more influential factor for the dissolution inhibition rather than hydrogen bonding by ester or carbonate functionality in a blocking group. To study structural effect on KRF lithographic performance, resists containing M-EEPHS were formulated and testified. Defects that are found in EEPHS based resist, such as LER (Line Edge Roughness) and top surface erosion at defocus can be solved by incorporation of carbornate, bulky acetal functionality or dissolution inhibition group. When hybrid system, which contained both M-EEPHS and poly[4-hydroxystyrene-co-tert-butyl acrylate-co-4-(3-cyano-1,5-di-tert-butyl carbonyl pentyl styrene)](P(HS-TBA-CBPS)) as an annealing type resin, were compared with the lithographic results of single polymeric system (M-EEPHS only), their performances were directly projected to those of blends of high activation type and low activation type resin.