Ldd transistor process having doping sensitive endpoint etching

Abstract

An LDD transistor is formed by using a process which insures that a layer of gate oxide is not inadvertently etched into and is not ruptured by static electrical charges. At least two thicknesses of gate electrode material of varying doping levels are formed over a layer of gate oxide which is above a semiconductor substrate. A chemical etch is utilized wherein by monitoring a ratio of chemical product and chemical reactant of the chemical etch reactions, specific endpoints in the etching of the gate electrode material can be easily detected. A small layer of gate electrode material is allowed to remain over the gate oxide layer during ion implanting and the formation and removal of gate sidewall spacers used in fabricating an LDD transistor. After formation of most of the LDD transistor, the remaining protective thickness of gate electrode material is removed and the exposed gate oxide layer is exposed to a final oxidizing anneal step. In other forms, an inverse-T gate structure LDD transistor is formed, and an LDD transistor is formed via a process having a reduced number of ion implants steps.