In this study,MFIS (Metal/Ferroelectric/Insulator/Semiconductor) capacitors whose structure is Al/BFO+Nb/HfO2/p-Si are investigatedby using Taguchi Method. The effects of leakage current, memory window, and signal-to-noise ratio (S/N ratio) are discussed by different process conditions. As a result, the leakage current and memory window indicate the better performance on th same process condition. The better conditions of this MFIS capacitoroccur in rapid thermal annealing (RTA) at 700 ° C, 5W direct current (DC)power of Nb sputtering and 15 of argon-to-oxygen ratio for laekage current and memory window.Oxygen vacancies were reduced bydoping niobium (Nb) that Nb ions replace ferrum (Fe) ions with RTA at 700°C. The more Nb dopesthe more Nb ions replace Fe ions. Butthe excessive Nb induces to increase the leakage current and reduce the memory widow.