A radio frequency (RF) semiconductor device may include a semiconductor-on-insulator substrate, and an RF ground plane layer on the semiconductor-on-insulator substrate including a conductive superlattice. The conductive superlattice may include stacked groups of layers, with each group of layers comprising stacked doped base semiconductor monolayers defining a doped base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent doped base semiconductor portions. The RF semiconductor device may further include a body above the RF ground plane layer, spaced apart source and drain regions adjacent the body and defining a channel region in the body, and a gate overlying the channel region.