Method for making semiconductor device comprising a superlattice with upper portions extending above adjacent upper portions of source and drain regions

Abstract

A method for making a semiconductor device may include providing a semiconductor substrate and forming at least one MOSFET by forming spaced apart source and drain regions and a superlattice on the substrate so that the superlattice is between the source and drain regions. The superlattice may include a plurality of stacked groups of layers. The superlattice may have upper portions extending above adjacent upper portions of the source and drain regions, and lower portions contacting the source and drain regions so that a channel is defined in lower portions of the superlattice. Each group of layers of the superlattice may include a plurality of stacked base semiconductor monolayers defining a base semiconductor portion and an energy band-modifying layer thereon. The energy-band modifying layer may include at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor. The method may further include forming a gate overlying the superlattice.