EEPROM DEVICE AND FABRICATING METHOD THEREOF TO IMPROVE SCATTERING OF THRESHOLD VOLTAGE OF CELL

摘要

PURPOSE: An EEPROM(electrically erasable and programmable read only memory) device is provided to improve scattering of a threshold voltage of a cell by guaranteeing a stable effective channel length even if a cell size is reduced. CONSTITUTION: A gate insulation layer(216a) for a memory transistor includes a tunnel insulation layer(214) formed on a semiconductor substrate(200) of the first conductivity type. A memory transistor gate(240) is formed on the gate insulation layer for the memory transistor. A gate insulation layer(216b) for a select transistor is formed on the semiconductor substrate, separated from the memory transistor gate. A select transistor gate(245) is formed on the gate insulation layer for the select transistor. A floating junction region(230) of the second conductivity type is formed in the semiconductor substrate under the tunnel insulation layer. A common source region(238) of the second conductivity type is formed in the semiconductor substrate at a side of the memory transistor gate, separated from the floating junction region. A bitline junction region(239) of the second conductivity type is formed in the semiconductor substrate at a side of the select transistor gate, separated from the floating junction region. The common source region is formed of only a single junction region of the first doping density. The junction of the common source region is shallower than the junction of the floating junction region and the bitline junction region.