Semiconductor device
For providing a cheap semiconductor memory device with improving reliability by level of a cell, in the place of escaping from defects on memory cells electrically, through such as ECC, and further for providing a cell structure enabling scaling-down in the vertical direction with maintaining the reliability, in a semiconductor memory device, upon which high-speeded read-out operation is required, a charge storage region is constructed with particles made from a large number of semiconductor charge storage small regions, each being independent, thereby increasing the reliability by the cell level.
1. A semiconductor device comprising a single nonvolatile memory cell, wherein the single nonvolatile memory cell includes:
a first region formed in a semiconductor substrate and serving as one of a source region and a drain region;
a second region formed in the semiconductor substrate and serving as another of the source region and the drain region;
an active region serving as a channel forming region and formed in the semiconductor substrate, in a first direction, between the first region and the second region;
a first gate electrode formed on a first part of the active region through a first insulator film;
a second gate electrode formed on a sidewall of the first gate electrode and on a second part of the active region through a second insulator,
wherein the first gate electrode and the second gate electrode are arranged, in the first direction, side by side in the active region such that the first part is positioned, in the first direction, between the first region and the second part and such that the second part is positioned, in the first direction, between the first part and the second region, and
wherein a plurality of crystalline grains are formed between the first part and the first gate electrode.
2. A semiconductor device according to claim 1 ,
wherein, in a write operation of the single nonvolatile memory cell, hot electrons which are generated near the active region between the first and second gate electrodes are injected into the plurality of crystalline grains.
3. A semiconductor device according to claim 2 ,
wherein, in the write operation, the source region is supplied with a first voltage, the drain region is supplied with a second voltage smaller than the first voltage, the first gate electrode is supplied with a third voltage larger than the second voltage, and the second gate electrode is supplied with a fourth voltage smaller than the third voltage.
4. A semiconductor device according to claim 1 ,
wherein the first insulator includes a first oxide film, a second oxide film, and a nitride film between the first and second oxide films.
5. A semiconductor device according to claim 4 ,
wherein a thickness of the nitride film is thicker than thicknesses of the first and second oxide films.
6. A semiconductor device according to claim 1 ,
wherein the first gate electrode is supplied with a fifth voltage smaller than the first voltage and the source and drain regions are supplied with a sixth voltage larger than the fifth voltage in an erase operation.
7. A semiconductor device according to claim 6 ,
wherein the fifth voltage is a negative voltage and the sixth voltage is a ground voltage.
8. A semiconductor device according to claim 1 ,
wherein the second gate electrode is formed of a sidewall structure.