We propose a nanocomposite resist system that incorporates sub-nm size fullerene C-60 molecules into a highly sensitive and moderately dry-etching resistant electron-beam positive resist, ZEP520, C-60 incorporation leads to carbon reinforcement in the original resist material and enhances resist performance for nanometer pattern fabrication. 10 wt% C-60 incorporated ZEP520 shows enhancements of etching resistance (similar to 15%), thermal resistance (similar to 30 degrees C), and mechanical resistance (3.5-5.5 in the aspect ratio). By applying this new resist system to x-ray mask fabrication, an ultrafine mask with the minimum dimension of 45 nm has been successfully fabricated.