Method of manufacturing mos transistors with gate electrodes formed in a packet of metal layers deposited upon one another

Abstract

Consistent with an example embodiment, a method of manufacturing a semiconductor device comprises MOS transistors having gate electrodes formed in a number of metal layers deposited upon one another. Active silicon regions having a layer of a gate dielectric and field-isolation regions insulating these regions from each other are formed in a silicon body. Then, a layer of a first metal is deposited in which locally, in a part of the active regions, nitrogen is introduced. On the layer of the first metal, a layer of a second metal is then deposited, after which the gate electrodes are etched in the metal layers. Before nitrogen is introduced into the first metal layer, an auxiliary layer of a third metal permeable to nitrogen is deposited an the first metal layer. Thus, the first metal layer can be nitrided locally without the risk of damaging the underlying gate dielectric.