Method for forming notch gate having self-aligned raised source/drain structure

Abstract

An innovative MOSFET having a raised source drain (RSD) is constructed prior to implanting source-drain dopants. The RSD structure thus built has a distinct advantage in that the offset from the RSD to the MOSFET channel is fully adjustable to minimize the overlap capacitance in the device. The RSD construction uses a selective epitaxial process to effectively reduce the drain-source resistance. This improvement is even more significant in thin-film SOI technology. Using an RSD, the film outside the channel area thickens which, in turn, reduces the parasitic resistance. The method of constructing such a structure includes the steps of: forming a notch gate on a top surface of a substrate; covering the notch gate and the top surface of the substrate with a conformal dielectric film; etching the dielectric film to expose an upper surface of the notch gate and selected exposed areas of the substrate; selectively growing silicon on the etched surface of the gate notch and on the etched surface of the substrate; implanting doping to form a drain-source area; forming spacers on the vertical walls of the notch gate; and forming a salicide on the notch gate and on the source and drain areas. The MOSFET device may be alternately be built without the formation of spacers.