Fet structures with trench implantation to improve back channel leakage and body resistance

Abstract

A field effect transistor (FET) structure on a semiconductor substrate which includes a gate structure having a spacer on a semiconductor substrate; an extension implant underneath the gate structure; a recessed source and a recessed drain filled with a doped epitaxial material; halo implanted regions adjacent a bottom of the recessed source and drain and being underneath the gate stack. In an exemplary embodiment, there is implanted junction butting underneath the bottom of each of the recessed source and drain, the junction butting being separate and distinct from the halo implanted regions. In another exemplary embodiment, the doped epitaxial material is graded from a lower dopant concentration at a side of the recessed source and drain to a higher dopant concentration at a center of the recessed source and drain. In a further exemplary embodiment, the semiconductor substrate is a semiconductor on insulator substrate.