A photoresist composition including a polymer is disclosed, wherein the polymer includes at least one monomer having the formula: where R.sub.1 represents hydrogen (H), a linear, branched or cyclo alkyl group of 1 to 20 carbons, a semi- or perfluorinated linear, branched or cyclo alkyl group of 1 to 20 carbons or CN; R.sub.2 represents an alicyclic group of 5 or more carbon atoms; X represents a methylene, ether, ester, amide or carbonate linkage; R.sub.3 represents a linear or branched alkylene group or semi- or perfluorinated linear or branched alkylene group with 1 or more carbon atoms; R.sub.4 represents hydrogen (H), methyl (CH.sub.3), trifluoromethyl (CF.sub.3), difluoromethyl (CHF.sub.2), fluoromethyl (CH.sub.2F), or a semi- or perflourinated aliphatic group; R.sub.5 represents trifluoromethyl (CF.sub.3), difluoromethyl (CHF.sub.2), fluoromethyl (CH.sub.2F), or a semi- or perfluorinated substituted or unsubstituted aliphatic group; n represents an integer of 1 or more; and OR.sub.12 represents OH or at least one acid labile group selected from a tertiary alkyl carbonate, a tertiary alkyl ester, a tertiary alkyl ether, an acetal and a ketal. A method of patterning a substrate is also disclosed, wherein the method includes: applying the photoresist composition mentioned above to the substrate to form a film; patternwise exposing the film to an imaging radiation source; and developing areas of the film to form a patterned substrate.