| 摘要 |
PURPOSE:To increase a current difference in a nonvolatile semiconductor memory by providing two floating gates and two control gates, and simultaneously electrons to one floating gate and emitting electrons from the other floating gate. CONSTITUTION:When information is written in a memory cell 60, a word line 47 and a bit line B45 are set to a program level. Accordingly, a drain a33 and a control gate a23 are raised to a potential reduced in Vth of a transistor e29 from the program level. A drain b34 and a control gate b24 become a GND level. A high electric field is applied to oxide film regions a25, b26, electrons are injected into a floating gate a21 of the region a25, and electrons are emitted from a floating gate a22 of the region b26. To read information of memory cell 60, word lines 48 and 47 are set to 'H' level, and currents flowing to transistors a27 and b28 are compared. Thus, even if the writing margin of the cell is reduced, sufficient reading margin is obtained to read it at a high speed. |
