DATA READ-OUT METHOD FOR SEMICONDUCTOR MEMORY, DATA WRITE-IN METHOD, AND DRIVING METHOD

摘要

PROBLEM TO BE SOLVED: To provide an optimum voltage setting method for reading out data in which retention caused by reduction of polarization of ferroelectric substance can be improved in a semiconductor memory in which a ferroelectric capacitor is connected to a gate of a field effect transistor FET. SOLUTION: Gate electric charges in a threshold voltage Vti of FET is assumed to be Qti. In polarization-voltage characteristic 21 when voltage of a polarization value of a ferroelectric capacitor is increased from a state of 0C/cm2, a voltage value at which a polarization value corresponding to Qti is obtained is assumed to be Vtf. Voltage of Vtf+Vti is applied to a control electrode and data is read out. An intersection of a gate electric charges-gate voltage characteristic 22 and the polarization-voltage characteristic 21 in read- out operation is an operation point in a state of a worst case 0C/cm2 after retention. By this voltage setting, data can be correctly read out until a polarization value is reduced to 0C/cm2.