The <i>V</i>th shift mechanism in MIFIS FeFET: A field-driven perspective

Hafnium-based ferroelectric field-effect transistor (FeFET) has demonstrated potential for 3D NAND applications. By introduction of a gate interlayer (GIL), the metal–interlayer–ferroelectric–interlayer–semiconductor (MIFIS) FeFET overcomes the classical limitation imposed by the coercive field (Ec) and ferroelectric thickness (tFE), enabling an expanded memory window (MW). While existing models attribute the MW to polarization and trapped charges scaled by ferroelectric and GIL capacitances, the field-driven threshold voltage (Vth) shift mechanism remains unexplored. To bridge the gap, we propose a two-step load-line model by incorporating a threshold field (Eth)-driven Vth shift mechanism. In this framework, we treat the GIL as a tunnel-switch layer controlled by Eth instead of an ideal capacitor. Simulations capture the device behavior and reveal an analytical expression for MW prediction, demonstrating a direct dependence of MW on Ec and Eth. This work establishes a field-driven perspective, offering a viable paradigm for designing and operating MIFIS FeFET devices.