Patent ID: 7215567
Filing Date: 2007-05-08
Classification: G11C

Abstract:
1. A ferroelectric memory device comprising: a memory cell group including: a write circuit for applying voltages equal to or higher than a coercive electric field of the ferroelectric thin film between the first bit line and the word line and between the second bit line and the word line at different timings when writing data in one of the field-effect transistors at a selected address; a read circuit for applying voltage equal to or lower than the coercive electric field of the ferroelectric thin film between the first bit line and the word line at the first read timing to detect a current flowing between the first bit line and the second bit line and applying voltage equal to or lower than the coercive electric field of the ferroelectric thin film between the second bit line and the word line at the second read timing different from the first read timing to detect a current flowing between the second bit line and the first bit line when reading data from the one of the field-effect transistors at the selected address; and a selection and control circuit for selecting the one of the field-effect transistors at a desired address when the write circuit performs the write operation and controlling voltage so that voltage equal to or higher than the coercive electric field of the ferroelectric thin film is applied between a word line and a bit line of the selected field-effect transistor and the voltage equal to or lower than the coercive electric field of the ferroelectric thin film is applied to remaining word lines and bit lines other than the word line and the bit line, while for selecting the one of the field-effect transistors at the desired address when the read circuit performs the read operation and controlling the voltage so that the voltage equal to or lower than the coercive electric field of the ferroelectric thin film is applied to the word lines and the bit lines of all of the field-effect transistors, the one of the field-effect transistors being an N-type field-effect transistor, the voltage being supplied from the selection and control circuit to the N-type field-effect transistor ranges between 0 and V, and coercive voltage corresponding to the coercive electric field of the ferroelectric thin film ranges between (1/2) V and V, and when writing data 1 in the N-type field-effect transistor at the selected address, the selection and control circuit supplying potential V to the word line of the selected address, potential (1/2) V to a word line at an unselected address, potential 0V to the bit line at the selected address, and potential (1/2) V to a bit line at the unselected address, and when writing data 0 in the N-type field-effect transistor at the selected address, the selection and control circuit supplying potential 0V to the word line of the selected address, potential (1/2) V the word line at the unselected address, potential V to the bit line at the selected address, and potential (1/2) V to the bit line at the unselected address.