CMOS devices are fabricated with a channel layer having minimized dopant fluctuation and diffusion. Embodiments include forming a dummy gate, on a substrate, between a pair of spacers, forming, in the substrate, a source and drain separated by a ground plane layer, removing the dummy gate from the substrate, forming a cavity between the pair of spacers, forming, after removal of the dummy gate, a channel layer on the substrate, forming a high-k layer on the channel layer and on side surfaces of the cavity, and forming a replacement gate in the cavity.