Metal-ferroelectric-insulator-silicon transistors [Fe-field-effect transistors (FeFETs)] with Al/Pb (Zr0.53,Ti0.47) O3/Y2O3/Si structure were fabricated. The wafers were pretreated with H2O2 before Y2O3 deposition and post-treated with HCl after Y2O3 deposition. With both treatments, the drain current ratio after writing pulses of ±8 V with a duration of 100 ns was measured as 105. The leakage current was reduced from 10-3 to 10-6 A/cm2. The FeFETs maintain a threshold voltage window of about 1.5 V after an elapsed time of 5000 s. The improvements are due to the reduction of the leakage current and the charge injection effect at the Y2O3/Si interface.