The core of the EEPROM memory cell is the tunnel oxide grown on an n(+) implant named capacitor implant which also electrically connects the cell drain. Different implant doses have been performed to optimize the cell junction characteristics in a 0.35 mum EEPROM technology. The impact on the quality and electrical characteristics of the tunnel oxide is hereafter analyzed. Furthermore, a modeling is presented, giving estimation of the oxide thickness and substrate superficial doping with a good correlation of these last values with SIMS measurements. As expected, a linear relation between the implant dose and the superficial doping has been found. (C) 2001 Elsevier Science Ltd. All rights reserved.