US Patent 7893487 Recessed channel transistor

A recessed channel transistor includes a single crystalline silicon substrate having a recessed portion, a bottom surface of the recessed portion including an elevated central portion, a channel doping region in the single crystalline silicon substrate, the channel doping region being under the bottom surface of the recessed portion, a gate structure in the recessed portion, and source/drain regions in the single crystalline silicon substrate at both sides of the recessed portion, the source/drain regions being spaced apart from the bottom surface of the recessed portion.