Semiconductor device with recessed channel array transistor (rcat) including a superlattice and associated methods

A method for making a semiconductor device may include forming at least one memory array including a plurality of recessed channel array transistors (RCATs) on a substrate, and forming periphery circuitry adjacent the at least one memory array and comprising a plurality of complementary metal oxide (CMOS) transistors on the substrate. Each of the CMOS transistors may include spaced-apart source and drain regions in the substrate and defining a channel region therebetween, and a first superlattice extending between the source and drain regions in the channel region. The first superlattice may include a plurality of stacked groups of layers, with each group of layers including 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. A gate may be over the first superlattice and between the source and drain regions.