Acid-catalyzed positive resist compositions which are imageable with 193 nm radiation (and possibly other radiation) at low energy levels are obtained using a polymer having acrylate/methacrylate monomeric units comprising a low activation energy moiety preferably attached to a naphthalene ester group. The resist allows the performance benefit of acrylate/methacrylate polymers with low activation energy for imaging thereby enabling improved resolution and reduced post-exposure bake sensitivity. The resist polymer also preferably contains monomeric units comprising fluoroalcohol moiety and a monomeric units comprising a lactone moiety.