Method for making semiconductor device including a superlattice and providing reduced gate leakage

Abstract

A method for making a semiconductor device may include forming shallow trench isolation (STI) regions in a semiconductor substrate defining an active region therebetween in the semiconductor substrate and a pad oxide on the active region. The method may further include removing at least some of the pad oxide, cleaning the active region to expose an upper surface thereof and define rounded shoulders of the active region adjacent the STI regions having an interior angle of at least 125°, and forming a superlattice on the active region. The superlattice may include a plurality of stacked groups of layers, 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. The method may further include forming a semiconductor circuit including the superlattice.