Transistor device with gate control layer undercutting the gate dielectric

Abstract

Techniques are disclosed for improving gate control over the channel of a transistor, by increasing the effective electrical gate length (L) through deposition of a gate control layer (GCL) at the interfaces of the channel with the source and drain regions. The GCL is a nominally undoped layer (or substantially lower doped layer, relative to the heavily doped S/D fill material) that can be deposited when forming a transistor using replacement S/D deposition. The GCL can be selectively deposited in the S/D cavities after such cavities have been formed and before the heavily doped S/D fill material is deposited. In this manner, the GCL decreases the source and drain underlap (X) with the gate stack and further separates the heavily doped source and drain regions. This, in turn, increases the effective electrical gate length (L) and improves the control that the gate has over the channel.