Narrow Sub-Fin Technique for Suppressing Parasitic-Channel Effect in Stacked Nanosheet Transistors

A new approach of narrowing sub-fin with little extra process cost for suppressing parasitic-channel-effect (PCE) on vertically-stacked horizontal gate-all-around (GAA) Si nanosheet field-effect-transistors (NS-FETs) is proposed. The proposed sub-fin design demonstrates systematical technical advantages by calibrated 3D TCAD simulation, including 70% reduction in sub-channel gate-induced drain leakage (GIDL) current, over 20% promotion for on-off current ratio (
$\text{I}_{\mathrm{ on}}/\text{I}_{\mathrm{ off}}$
) as well as improvement in sub-threshold slope (SS). The revealed narrow sub-fin offers nearly 10% on-state current promotion and gate controllability improvement for the NS-FETs with relatively lower ground-plane-concentration. The narrow sub-fin technique provides a new approach for suppressing PCE in the NS-FETs and indicates a promising supplementary technology adopted for the optimization of NS-FET fabrication process in sub-3nm technology node.