Gate structure of metal oxide semiconductor field effect transistor

Abstract

The present invention provides an alloy system as metal gate material of MOSFET devices that can solve the issue of work function incompatibility of metal gate and then can achieve low threshold voltage of surface channel MOSFETs effectively to satisfy the requirement of low voltage and high performance operation. To achieve this purpose, a chemically inert and thermally stable element, platinum (Pt), with high work function is selected as the basic component, which is doped with low work function element, such as tantalum (Ta), or titanium (Ti) to various atomic ratios. The work function can be adjusted to arbitrary value depends on the atomic ratio of element. The metal alloy can be deposited with co-sputtering or co-evaporation method of physical vapor deposition to synthesize the suitable alloy of platinum (Pt) by adjustment of deposition rate of platinum (Pt) target and relative low work function metallic target, that can also be employed by simple sputtering on pre-formed platinum (Pt)—alloy target.