Sandwich silicidation for fully silicided gate formation

Abstract

When forming field effect transistors, a common problem is the formation of a Schottky barrier at the interface between a metal thin film in the gate electrode and a semiconductor material, typically polysilicon, formed thereupon. Fully silicided gates are known in the state of the art which may overcome this problem. The claimed method proposes an improved fully silicided gate achieved by forming a gate structure including an additional metal layer between the metal gate layer and the gate semiconductor material. A silicidation process can then be optimized so as to form a lower metal silicide layer comprising the metal of the additional metal layer and an upper metal silicide layer forming an interface with the lower metal silicide layer.