| 摘要 |
In a memory array of memory cells each having at least a gate, a substrate, a source and a drain, a writing operation is effected when the substrate and the source and drain are at the same potential and when a potential difference Vp exists between the potential of the substrate and the source and drain and that at the gate. The stored contents are erased when a potential difference Vp exists between the gate and the substrate. The stored condition is prevented from changing when a potential difference Vp exists between the substrate and the gate and when a potential difference Vwd exists between the substrate and the source and drain. When such a memory array is partially erased, cells not to be erased are sequentially driven by applying a voltage Vwd between the source and drain and the substrate of the cell, applying a voltage Vp between the gate and the substrate of the cell, and applying the same potential to the substrate and the gate of the cell.
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