A metal-ferroelectric [SrBi2Ta2O9 (SBT)]-high-k-insulator(PrOx)-semiconductor(Si) structure has been fabricated and evaluated as a key part of metal-ferroelectric-insulatorsemiconductor-field-effect-transistor MFIS-FET memory, aiming to improve the memory retention characteristics by increasing the dielectric constant in the insulator layer and suppressing the depolarization field in the SBT layer. A 20-nm PrOx film grown on Si(100) showed both a high ε of about 12 and a low leakage current density of less than 1×10−8 A/cm2 at 1.5 MV/cm. A 400-nm SBT film prepared on PrOx/Si shows a preferentially oriented (105) crystalline structure, grain size of about 130 nm and surface roughness of 3.2 nm. A capacitance–voltage hysteresis is confirmed on the Pt/SBT/PrOx/Si diode with a memory window of 0.3 V at a sweep voltage width of 12 V. The memory retention time was about 1×104 s, comparable to the conventional Pt/SBT/SiOxNy(SiON)/Si. The gradual change of the capacitance indicates that some memory degradation mechanism is different from that in the Pt/SBT/SiON/Si structure.