We have made ferroelectric memory capacitors by depositing aSrBi2Ta2O9thin film on a Si substrate separated by an ultrathin buffer layer of silicon nitride film. The hysteresis in the capacitance–voltage curves suggests a sizable memory window of 2 V with a programming voltage swing of±7 V.The switching time is estimated to be on the order of nanosecond based on the results of a one-shot pulse experiment. The results from the fatigue test indicate a slight degradation of the memory window after1011switching cycles. These properties are encouraging for the development of ferroelectric memory transistors. ©1998 American Institute of Physics.