Metal oxide semiconductor transistors having a polysilicon gate electrode with nonuniform doping in source-drain direction

摘要

The gate electrode of a polysilicon gate MOS transistor-the transistor having either a thin film polysilicon substrate or a bulk monocrystalline substrate-has a pair of contiguous regions: a heavily doped gate electrode region near the source, and a lightly doped gate electrode region near the drain. The gate electrode region near the drain is thus doped significantly more lightly, in order to reduce electric fields in the channel region in the neighborhood of the drain (and hence reduce field induced leakage currents) when voltages are applied to turn transistor OFF. At the same time, sufficient impurity doping is introduced into the gate electrode region near the source in order to enable the transistor to turn ON when other suitable voltages are applied.