Granular nanostructure of electron beam resist had limited the ultimate resolution of electron beam lithography. The authors report a thermal process to achieve a uniform and homogeneous amorphous thin film of polymethyl methacrylate electron resist. This thermal process consists of a short time-high temperature backing process in addition to precisely optimized development process conditions. Using this novel process, they patterned arrays of holes with diameter smaller than 5 nm and line edge roughness and surface roughness of the resist reduced to 1 nm and 100 pm, respectively. In addition, etch resistance of the resist verified and the resist pattern transferred to a metal thin film.