An angled gas cluster ion beam (“GCIB”) and methods for using the same are disclosed. Gas clusters are ionized to create a gas cluster beam directed towards a semiconductor wafer. The semiconductor wafer is positioned so that it intercepts the gas cluster beam at an angle that is non-perpendicular to the beam, so that the gas cluster ions in the beam react with structures on the semiconductor wafer asymmetrically, allowing for asymmetrical deposition on or etching of material thereon. According to one embodiment, GCIB is used to form asymmetric spacers having different materials, different thicknesses, or both.