Breaking the Constant-Thickness Assumptions in Ferroelectric Negative Capacitance Transistors

Ferroelectric (FE) oxides are key design parameters for developing Negative Capacitance Field-Effect Transistors (NCFETs). The properties of FE oxides, such as remnant polarization ( P r ) and coercive field ( E c ), are greatly affected by the thickness of the FE film. However, most existing analyses of NCFETs assume constant ferroelectric parameters (CFP) independent of thickness, which can lead to an overestimation of device performance. In this study, we develop, for the first time, a comprehensive analytical and simulation framework that incorporates the influence of thickness-dependent ferroelectric parameters (TDFP) on the negative capacitance (NC) in Forksheet FETs (FSFET). To accurately capture device performance, the NCFSFET is modeled using a Landau–Khalatnikov approach. The analytical model and simulation approach highlight device-level metrics, including surface potential, ON current, OFF current, transfer characteristics, and output characteristics, for ferroelectric thickness variations ranging from 2 to 5 nm. By integrating experimentally validated thickness-polarization field correlations, the model reveals a significant deviation between CFP and thickness-dependent approaches, with up to 100% overestimation of ON current and 93% underestimation of leakage current when constant parameters are used. The findings highlight that realistic modeling of ferroelectric thickness is crucial for predicting electrostatic stability, DIBL, and capacitance behavior in scaled NCFETs. This study establishes a pathway toward more reliable and physically consistent modeling of negative capacitance devices for future neuromorphic and unconventional computing systems.