Molecular weight distribution effects of novolak resin‐based chemical amplification negative resist systems are investigated for electron‐beam lithography. The resist systems investigated consist of onium salts as an acid generator, a methoxymethyl melamine crosslinker, and a conventional/fractionated novolak resin matrix. Delineated patterns of both types of resist systems are compared to evaluate submicron‐scale resolution. The conventional novolak resin‐based system shows higher contrast than the fractionated one. High aspect ratio patterns are resolved for the conventional novolak‐based resist, whereas poor results are obtained for the fractionated resin‐based one on the submicron scale. Very thin films (30 nm) of both resist systems are delineated with a finely focused electron beam (diameter: approximately 2 nm at 5 kV) from a scanning electron microscope. Nanometer‐scale edge roughness (nanoedge roughness) is observed for the conventional novolak resin‐based resist. On the contrary, the degree of nanoedge roughness is greatly reduced for the fractionated one.