| 摘要 |
PURPOSE:To improve writing characteristics without miniaturization of an element and without decrease in reliability, by providing a first gate insulating film at a part closer to a source region on a channel region, and providing a second gate insulating film, which is thinner than the first gate insulating film as a unitary body with the first gate insulating film on the same channel region. CONSTITUTION:Second conductivity type source and drain regions 34 and 35 are provided on a first conductivity type semiconductor substrate 21. A first gate insulating film 25 is provided at a part closer to the source region 34 on a channel region between the source and drain regions 34 and 35. A second gate insulating film 26, which is thinner than the first gate insulating film 25, is provided on the same channel region as a unitary body with the first gate insulating film 26. On the first and second gate insulating films 25 and 26, a floating gate electrode 33, a third gate insulating film 32 and an outer gate electrode 31 are sequentially provided. Thus, the field intensity in the gate direction in the vicinity of the drain region 35 is increased, and the quantity of channel hot electrons can be increased. Therefore, the quantity of the electrons, which are injected in the floating gate electrode 33, can be increased and the writing characteristics of a PROM can be improved.
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