Lightly doped drain transistor device having the polysilicon sidewall spacers

摘要

A lightly doped drain (LDD) transistor device structure and a method of fabricating same are described. A silicon substrate is provided which has a trench formed therein. Polysilicon sidewall spacers are formed on the side walls of the trench. Silicon dioxide sidewall spacers are formed on the side walls of the polysilicon sidewall spacers. A gate oxide layer is formed on the bottom of the trench by oxidation. A polysilicon gate layer is formed filling the trench. Impurities are implanted into the silicon substrate to simultaneously form heavily doped source/drain areas in spaced apart portions of the silicon substrate adjacent to the polysilicon sidewall spacers to improve the conductivity of the polysilicon gate layer, and form lightly doped source/drain areas in spaced apart portions of the silicon substrate under the silicon dioxide sidewall spacers.