Semiconductor memory device having memory cells each capable of storing three or more values

摘要

Memory cells are used which each have a MOSFET that holds an information voltage of three or more values at its gate, a writing transistor that supplies the information voltage of three or more values to the gate of the MOSFET, and a reading transistor connected in series with the MOSFET. A plurality of reference voltages corresponding to the information voltage of three or more values are applied from a source line to the sources of the MOSFETs, so that digital data is produced by a combination of on-state/off-state of the MOSFET and the plurality of reference voltages or that the source voltages themselves of the MOSFETs are produced as read voltages.