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US 5,852,312 AGranted
Flash eeprom cell
AssigneeHyundai Electronics Industries Co., Ltd.
InventorByung Jin Ahn
Life of this patent
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Abstract
The flash EEPROM cell of split-gate type according to the present invention can prevent the degradation of the tunnel oxide film of the cell due to the band-to-band tunneling and the secondary hot carrier which are generated by a high electric field formed at the overlap region between the junction region and the gate electrode when programming and erasure operations are performed by a high voltage to the structure in which the tunneling region is separated from the channel with a thick insulation film.
Claims5
A flash EEPROM cell comprising:
- a silicon substrate having a first and a second field oxide layers;
- a gate oxide layer, a control gate and an interpoly insulating layer formed on a portion of said silicon substrate between said first and said second field oxide layers in stack structure;
- a floating gate oxide layer on a surface of said silicon substrate between said control gate and said second field oxide layer,
- so that portion of said silicon substrate adjacent to said second field oxide layer is exposed, wherein a portion of said floating gate oxide layer near said control gate is formed thicker than other portion of said floating gate oxide layer near said second field oxide layer;
- a buried drain region formed under said second field oxide layer;
- a drain region formed under said floating gate oxide layer, wherein said drain region is connected to said buried drain region;
- a source region formed in a portion of said silicon substrate between said control gate and said first field oxide layer;
- a tunnel oxide layer formed to isolate said silicon substrate, said interpoly insulating layer and said control gate;
- and
- a floating gate formed on said tunnel oxide layer.
7 more elements
Dependencies are inferred from the claim text.