| 摘要 |
PURPOSE: To prevent that an erasing time is lengthened without applying over- electric-field to a tunnel insulation film even if erasing speed is different by dispersion of manufacturing, in a memory having a floating gate. CONSTITUTION: In a non-volatile semiconductor memory provided with a plurality of memory cells having a floating gate, this device monitors a leak current of a memory cell being in erasure, by monitoring a state of a memory cell being in erasure and controlling erasure voltage applied to a control gate in accordance with a progress state of erasure. When a cell leak current is small, as many electrons are left in a control gate, erasure voltage applied to a cell is made low and an electric field of a tunnel insulation film is suppressed. On the contrary, when a cell leak current is large, as few electrons are left in a floating gate, an electric field is not excessively generated in a tunnel insulation film even if erasure voltage is made higher, erasure speed can be increased.
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