Semiconductor device having a dual gate electrode and methods of forming the same

A method of forming a semiconductor device, the method comprising:

• providing a substrate including first and second regions;
• forming a gate insulating layer on a surface of the substrate;
• forming a first gate electrode formed of a first metal silicide on the gate insulating layer in the first region;
• and
• forming a second gate electrode formed of a second metal silicide including a metal the same as that of the first metal silicide on the gate insulating layer of the second region, wherein the gate insulating layer is formed of an insulating material which brings about a Fermi pinning effect increasing or decreasing intrinsic work functions of the first and second metal silicides, and wherein the first gate electrode formed of the first metal silicide has a height that is less than a height of the second gate electrode formed of the second metal silicide, such that the first metal silicide has a lower silicon concentration than the second metal silicide so that the Fermi pinning effect provided to the first gate electrode is less effective than that provided to the second gate electrode.

A semiconductor device comprising:

• a substrate including a PMOS transistor and a NMOS transistor region;
• a first gate electrode disposed on the substrate in the PMOS transistor region and formed of a first metal silicide;
• a second gate electrode disposed on the substrate in the NMOS transistor region and formed of a second metal silicide including the same metal as that of the first metal silicide;
• a gate insulating layer interposed between the substrate and the first gate electrode, and between the substrate and the second gate electrode,
• wherein the gate insulating layer brings about a Fermi pinning effect decreasing an intrinsic work function of the first and second metal silicides,
• wherein the first metal silicide has a lower silicon concentration that the second metal silicide so that the Fermi pinning effect provided to the first gate electrode is less effective than that provided to the second gate electrode, and
• wherein an intrinsic work function of a metal included in the first and second metal silicides is larger than that of the first and second metal silicides.