Hysteresis window observed in ferroelectric negative capacitance field-effect transistors (NCFETs) have been a persistent challenge in the development of reliable logic circuits, often leading to abnormal operational conditions. Despite its significance, the underlying factors driving this hysteresis phenomenon remain elusive. In this study, we employ the quasi-static L–K equation in conjunction with the Mott–Gurney law to study the impact of V migration on the hysteresis behavior of NCFETs, based on a surface potential-based physical model. Compared with pristine NCFET, the difference of peak voltages in value of 1.3 V was achieved in V-involved sample upon reverse and forwards scanning. This result clearly suggests that the relaxation of charged oxygen vacancies significantly affects the threshold voltage under applied sweeping voltages, providing a plausible explanation for the emergence of hysteresis windows in NCFETs. A replacement of the conventional oxide layer with a buffer layer containing high-mobility ions is proposed to adjust the hysteresis window. Importantly, in accordance with the theoretical predictions, the increased ion mobility results in a substantial reduction in the hysteresis window observed in NCFETs. Our proposed physical mechanism, elucidating the space-charge-induced hysteresis behavior, provides fresh insights for mitigating hysteresis effects, thereby advancing the potential applications of NCFETs in logic circuits.