A finned semiconductor structure including sets of relatively wide and relatively narrow fins is obtained by employing hard masks having different quality. A relatively porous hard mask is formed over a first region of a semiconductor substrate and a relatively dense hard mask is formed over a second region of the substrate. Patterning of the different hard masks using a sidewall image transfer process causes greater lateral etching of the relatively porous hard mask than the relatively dense hard mask. A subsequent reactive ion etch to form semiconductor fins causes relatively narrow fins to be formed beneath the relatively porous hard mask and relatively wide fins to be formed beneath the relatively dense hard mask.