Method of line roughness improvement by plasma selective deposition

A substrate is provided with a patterned layer, for example, a photo resist layer, which may exhibit line roughness. In one exemplary embodiment, the patterned layer may be an extreme ultraviolet (EUV) photo resist layer. In one method, selective deposition of additional material is provided on the EUV photo resist layer after patterning to provide improved roughness and lithographic structure height to allow for more process margin when transferring the pattern to a layer underlying the photo resist. The additional material is deposited selectively thicker in areas above the photo resist than in areas where the photo resist is not present, such as exposed areas between the photo resist pattern. Pattern transfer to a layer underlying the photo resist may then occur (for example via an etch) while the patterned photo resist and additional material above the photo resist may collectively operate as an etch mask.