| 摘要 |
PURPOSE:To contract a memory cell by forming an erasable/writable floating gate type memory cell in a 1-transistor structure. CONSTITUTION:A memory cell has a thin portion in a first insulating film 3 directly under a floating gate 4, and a second insulating film 5 on the gate 4 and a third insulating film 7 on a semiconductor substrate half region of a drain 2 side are integrally formed. A control gate 6 and a select gate 8 are formed by forming in advance one conductivity type polycrystalline silicon film, ion implanting impurity atoms to invert it to reverse conductivity type to form the layers. In the thus formed floating gate type memory cell, a high voltage is applied to the gate 6 and the gate 8 at erasing time, and a low voltage is applied to the control gate and a high voltage is applied to the select gate at writing time. In this case, the control gate and the select gate are never shortcircuited due to the reverse bias of a diode.
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