Abstract: Reducing line edge roughness by particle beam exposure is generally described. In one example, a method includes forming one or more line structures on a surface of a semiconductor substrate, aligning the one or more line structures to a beam path of a particle beam such that particles of the particle beam travel within 45 degrees of parallel to a lengthwise direction of the one or more line structures, and exposing the one or more line structures to the particle beam to reduce line edge roughness of the one or more line structures wherein an incident angle of the particle beam to the surface of the semiconductor substrate is between about 45 degrees and about 90 degrees, where 0 degrees is normal to the surface of the semiconductor substrate.