Methods and structures for forming finFETs of different semiconductor composition and of different conductivity type on a same wafer are described. Some finFET structures may include strained channel regions. FinFETs of a first semiconductor composition may be grown in trenches formed in a second semiconductor composition. Material of the second semiconductor composition may be removed from around some of the fins at first regions of the wafer, and may remain around fins at second regions of the wafer. A chemical component from the second semiconductor composition may be driven into the fins by diffusion at the second regions to form finFETs of a different chemical composition from those of the first regions. The converted fins at the second regions may include strain.