EEPROM memory cell and corresponding manufacturing method
AssigneeSTMicroelectronics S.r.l.
InventorFederico Pio
Life of this patent
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Abstract
An EEPROM memory cell integrated in a semiconductor substrate comprises a floating gate MOS transistor having a source region, a drain region, and a gate region projecting from the substrate and is isolated from the substrate by an oxide layer including a thinner tunnel portion and heavily doped regions formed under said tunnel portion and extending to beneath the drain region, and a selection transistor having a source region, a drain region and a gate region, wherein said source region is heavily doped and formed simultaneously with said heavily doped regions.
Claims13
A method for forming EEPROM cells comprising a floating gate MOS transistor having a source region, a drain region, a gate region projecting from a substrate and being isolated from the substrate by an oxide layer which includes a thinner tunnel portion, and a heavily doped region formed under said tunnel portion and extending to beneath the drain region, the heavily doped region including a tunnel region directly below the tunnel portion, the method comprising:
- forming both said source region and said heavily doped region in a single dopant implantation step that is the only dopant implantation of the tunnel region;
- forming the gate region over the tunnel region and the tunnel portion of the oxide layer;
- and
- implanting the drain region with a lighter doping than that of the source and heavily doped regions after implanting the source and heavily doped regions.
A method for forming EEPROM cells comprising a floating gate MOS transistor having a source region, a drain region, a gate region projecting from a substrate and being isolated from the substrate by an oxide layer including a thinner tunnel portion, and a heavily doped region formed directly under said tunnel portion, the method comprising:
- forming simultaneously said source region and said heavily doped region using a single dopant implantation step that is the only dopant implantation directly under the tunnel portion;
- forming the gate region after forming the source and heavily doped regions;
- and
- implanting the drain region with a lighter doping than that of the source and heavily doped regions after implanting the source and heavily doped regions.
Dependencies are inferred from the claim text.