To provide a nonvolatile semiconductor device capable of significantly increasing an amount of writing at a low voltage with no increase in an area of an element and controlling of a control gate voltage, and further, capable of performing sufficient writing in a stable manner.
A semiconductor memory element which performs writing by drain avalanche hot electron is an MOS transistor that contains a first semiconductor layer of a second conductivity type which is formed on a first conductivity type semiconductor substrate, a floating gate provided on the first semiconductor layer through an insulating film, a channel region formed on the surface of the first semiconductor layer at the lower part of the floating gate, and a source region and a drain region of a first conductivity type provided on the first semiconductor layer so as to contact the channel region. In the semiconductor memory element, the channel region has two or more kinds of carrier concentration distributions.
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TSUMURA KAZUHIRO
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Noriaki Uchino
Nobuyuki Kimura