We developed high-performance metal-ferro-electric-insulator-semiconductor (MFIS) structures with a thin Al 2 O 3 layer deposited on Si 3 N 4 buffer layer. The Al 2 O 3 were deposited by atomic layer deposition technique and the Si 3 N 4 were made by the direct nitridation of Si substrate using atomic nitrogen radicals. Since the buffer Si 3 N 4 was made perfectly damage-free and hydrogen-free, we can perform high temperature oxidation to eliminate defects in Al 2 O 3 and ferroelectric films down to the negligible level. On the stacked buffer layer, we deposited highly c-axis oriented Bi 3.25 La 0.75 Ti 3 O 12 film and fabricated MFIS structure. With the help of the high insulating property of a buffer layer and a highly c-axis oriented ferroelectric film, we succeeded to realize the large memory windows together with the long retention characters in the Pt/Bi 3.25 La 0.75 Ti 3 O 12 /Al 2 O 3 /Si 3 N 4 /Si MFIS structure.