A CMOS image sensor may include a first semiconductor chip including image sensor pixels and readout circuitry electrically connected thereto, and a second semiconductor chip coupled to the first chip in a stack and including image processing circuitry electrically connected to the readout circuitry. The processing circuitry may include a plurality of transistors each including spaced apart source and drain regions and a superlattice channel extending between the source and drain regions. The superlattice channel may include 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 a non-semiconductor monolayer(s) constrained within a crystal lattice of adjacent base semiconductor portions. Each transistor may further include a gate insulating layer on the superlattice channel and a gate electrode on the gate insulating layer.
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