  The ferroelectric polarization switching in ferroelectric hafnium zirconium
oxide (Hf0.5Zr0.5O2, HZO) in the HZO/Al2O3 ferroelectric/dielectric stack is
investigated systematically by capacitance-voltage and polarization-voltage
measurements. The thickness of dielectric layer is found to have a determinant
impact on the ferroelectric polarization switching of ferroelectric HZO. A
suppression of ferroelectricity is observed with thick dielectric layer. In the
gate stacks with thin dielectric layers, a full polarization switching of the
ferroelectric layer is found possible by the proposed leakage-current-assist
mechanism through the ultrathin dielectric layer. Theoretical simulation
results agree well with experimental data. This work clarifies some of the
critical parts of the long-standing confusions and debating related to negative
capacitance field-effect transistors (NC-FETs) concepts and experiments.
