Impacts of metal interlayer on Negative Capacitance Transistors

Two structures of ferroelectric negative capacitance field-effect transistors (NCFET) show difference in their electrical characteristics. TCAD numerical simulation is used to reveal the origins of these differences from a more physical perspective. It is found that a metal interlayer in NCFETs changes the local charge matching into total charge matching, leading to an increase of the threshold voltage with the drain voltage and a decrease of the subthreshold current. At the same time, the metal interlayer induces a large electric field along the channel direction, especially for ferroelectric materials with small remnant polarizations, hence a higher on state current.