Device structures for a fin-type field-effect transistor (FinFET) and methods for fabricating a device structure for a FinFET. A fin comprised of a semiconductor material having a first crystal structure is formed. A dielectric layer is formed that includes an opening aligned with the fin. A dummy gate structure is removed from the opening in the dielectric layer. After the dummy gate structure is removed, a section of the fin aligned with the opening is implanted with non-dopant ions to amorphize the first crystal structure of the semiconductor material of the fin. After the section of the fin is implanted, the section of the fin is annealed such that the semiconductor material in the section of the fin recrystallizes with a second crystal structure incorporating internal strain.