A semiconductor device may include at least one fin field-effect transistor (FINFET) comprising a fin, source and drain regions adjacent opposite ends of the fin, and a gate overlying the fin. The fin may include at least one superlattice including a plurality of stacked groups of layers. Each group of layers may include a plurality of stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions.