An approach to forming fins for a semiconductor device on a silicon-on-insulator wafer. The approach includes depositing a layer of mandrel material and etching the layer of mandrel material to form a mandrel. The approach includes depositing a layer of a dielectric material on the semiconductor layer and around the mandrel and etching the layer of the dielectric material to form one or more spacers next to the sidewalls of the mandrel, followed by removing the mandrel. Additionally, the approach includes depositing a layer of amorphous semiconductor material around said one or more spacers and heating it to transform into a layer of re-crystallized semiconductor material through solid phase epitaxy. Furthermore, the approach includes removing portions of the layer of re-crystallized semiconductor material from each of the horizontal surfaces of the silicon-on-insulator wafer including the area where the one or more spacers were removed to form one or more fins.