SEMICONDUCTOR DEVICE
A semiconductor device includes a field-effect transistor on a substrate. The field-effect transistor includes a gate insulating film and a gate electrode. The gate electrode has a laminated structure including a first electrode layer made of a first metal, a second electrode layer made of a second metal, and a third electrode layer made of a silicon layer. The second metal is a material having a workfunction for alleviating band discontinuity between the first electrode layer and the third electrode layer, with respect to a majority carrier of the silicon layer.
1 . A semiconductor device comprising:
a semiconductor substrate;
an NMOS including a first gate insulating film on the substrate and a first gate electrode including a layer of a first metal on the first gate insulating film, a layer of a second metal on the layer of the first metal, and a layer of n-type doped polysilicon on the layer of the second metal; and
a PMOS including a second gate insulating film on the substrate and a second gate electrode including a layer of a third metal on the second gate insulating film, a layer of a fourth metal on the layer of the third metal, and a layer of p-type doped polysilicon on the layer of the fourth metal,
wherein EF 1 which is a workfunction of the first metal, EF 2 which is a workfunction of the second metal, EF 3 which is a workfunction of the third metal, EF 4 which is a workfunction of the fourth metal, EfN which is a Fermi level of the n-type doped polysilicon, and EfP which is a Fermi level of the p-type doped polysilicon satisfy the following expressions (1) and (2):
| EF 1− EfN|>EF 2− EfN ; and (1)
| EF 3− EfP|>EfP−EF 4. (2)
2 . The semiconductor device according to claim 1 , wherein the first metal and the third metal are made of the same metal.
3 . The semiconductor device according to claim 1 , wherein the first metal has a workfunction of 4.2 to 4.9 eV and the second metal has a workfunction of 3.0 to 4.3 eV.
4 . The semiconductor device according to claim 1 , wherein the first metal is at least one metal selected from the group consisting of TiN, W, TaN, TaSiN, Ru and TiAlN and the second metal is at least one metal selected from the group consisting of Tb, Y, Nd, La, Sc, Lu, Mg, Ti, Hf, Al, Mn, Zr, Bi, Pb, Ta, Ag, V, Zn, Ti and Nb.
5 . The semiconductor device according to claim 1 , wherein the third metal has a workfunction of 4.2 to 4.9 eV and the fourth metal has a workfunction of 5.0 to 6.0 eV.
6 . The semiconductor device according to claim 1 , wherein the first metal is at least one metal selected from the group consisting of TiN, W, TaN, TaSiN, Ru and TiAlN and the fourth metal is at least one metal selected from the group consisting of Te, Re, Rh, Be, Co, Au, Pb, Ni, Ir and Pt.
7 . The semiconductor device according to claim 1 , wherein the first and second gate insulating films include at least one material selected from the group consisting of HfO 2 , ZrO 2 , HfSiON, La 2 O 3 and HfAlO.