A method of manufacturing a three dimensional FET device structure includes: providing a substrate having a semiconductor layer on an insulator layer; forming three dimensional fins in the semiconductor layer; applying a masking material to a first fin while exposing a second fin; applying a hydrogen atmosphere to the substrate and exposed second fin, the hydrogen atmosphere causing the exposed second fin to reflow and change shape; removing the masking material from the first fin; and forming a gate to wrap around each of the first and second fins. The first and second fins are formed having a device width such that the first fin having a first device width and a second fin having a second device width with the first device width being different than the second device width.