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.