| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a non-volatile semiconductor memory in which a writing time can be shortened and threshold voltage can be controlled highly accurately. SOLUTION: A threshold value detecting circuit 60 is provided at an output side of a sense amplifier 50, at the time of writing, a writing pulse is applied to a selection memory cell, after applying a pulse, threshold voltage of the selection memory cell is detected, a detected value is discriminated by a control circuit 80, a pulse width is increased with the prescribed increment rate and the pulse is applied until threshold voltage reaches the prescribed range including a target value VTH, Since after threshold voltage reaches the prescribed range, an increment rate of the pulse width is made small, applying a pulse is repeated until threshold voltage reaches the target value VTH or near the value, the number of times of applying a pulse can be largely reduced at the time of writing, a writing time can be shortened, threshold voltage of a memory cell can be controlled highly accurately.</p> |
