| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce a disturbance applied to a dummy cell and to improve reliability in a multilevel nonvolatile semiconductor memory of a system making a floating gate type MOS transistor a memory cell and using the dummy cell for forming a reference signal of a sense amplifier. SOLUTION: In differential amplifiers 11-13 constituting the sense amplifier 3, a signal from a bit line is inputted to signal input terminals S11-S13, and the reference input signal of the dummy cell is inputted to reference input terminals R11-R13. When the signal in the memory cell is read out by a word line 1W2 and a bit line 1B2, the dummy cells 1D21-1D23 are selected by the word line 1W2 to be inputted to the differential amplifier. When the word line 1W1 is selected, the dummy cells 1D11-1D13, and when the word line 1Wm is selected, the dummy cells 1Dm1-1Dm3 are selected.</p> |
