Patent ID: 7754570
Filing Date: 2010-07-13
Classification: H01L

Abstract:
1. A semiconductor device having a plurality of field effect transistors each of which comprising: a semiconductor substrate; a Si-containing gate electrode provided on said semiconductor substrate; and a gate insulating film provided between said semiconductor substrate and said Si-containing gate electrode, so as to contact with said Si-containing gate electrode, wherein each of said plurality of field effect transistors has at least one metal selected from the group consisting of Hf, Zr, Al, La, Pr, Y, Ti, Ta and W contained at the interface between said Si-containing gate electrode and said gate insulating film, wherein said interface separates said Si-containing gate electrode from said gate insulating film with no more than a single atomic layer of said metal, wherein said at least one metal bonds with silicon in said Si-containing gate electrode at a surface of said Si-containing gate electrode, wherein a work function of said metal changes nonlinearly, with changing concentration of said metal, from an end of a conduction band of Si or an end of a valence band of Si to an energy level that is different from a work function of a mass of said metal, and wherein at least one of said field effect transistors has an impurity concentration in the channel region of said one of said field effect transistor differed from impurity concentration in the channel regions of the other field effect transistor.