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

Abstract

Method of manufacturing a semiconductor device comprising MOS transistors having gate electrodes (15, 16) formed in a number of metal layers (8, 9, 13; 8, 12, 13) deposited upon one another. In this method, active silicon regions (4, 5) provided with a layer of a gate dielectric (7) and field-isolation regions (6) insulating these regions with respect to each other are formed in a silicon body (1). Then, a layer off a first metal (8) is deposited in which locally, at the location of a part of the active regions (4), nitrogen is introduced. On the layer of the first metal, a layer of a second metal (13) 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 (9) which is permeable to nitrogen is deposited on the first metal layer. Thus, the first metal layer can be nitrided locally without the risk of damaging the underlying gate dielectric. Substantial changes of the metal work function are possible, and a semiconductor device comprising NMOS and PMOS can be realized.

Dependencies are inferred from the claim text.