US Patent 7282417 Ion doping method to form source and drain

An ion doping method to form source and drain is disclosed. First form a gate structure and a gate spacer on a semiconductor substrate, and then use dielectric layer having trenches therein to define heavily ion-doped positions and use a Y-shaped polysilicon layer formed in the trenches. Perform an ion implantation, by using the polysilicon layer, gate spacer and dielectric layer as a barrier layer, to naturally form ion doped regions of source/drain, so as to make components, which are minimized in the increased packing density, still have a gate structure keeping an enough channel length.