Embodiments of the invention are directed to a method and resulting structures for a steep-switch vertical field effect transistor (SS-VFET). In a non-limiting embodiment of the invention, a semiconductor fin is formed vertically extending from a bottom source or drain region of a substrate. A top source or drain region is formed on a surface of the semiconductor fin and a top metallization layer is formed on the top source or drain region. A bi-stable resistive system is formed on the top metallization layer. The bi-stable resistive system includes an insulator-to-metal transition material or a threshold-switching selector. The SS-VFET provides a subthreshold switching slope of less than 60 millivolts per decade.