Patent ID: 7425497

Claim:
A method of changing workfunction of a conductive stack comprising: providing a material stack that comprises a Hf-based dielectric having a dielectric constant of greater than silicon dioxide, a metal-containing material including at least one metal selected from Ti, Zr, Hf, V, Nb and Ta located above said Hf-based dielectric, and a conductive electrode located above said metal-containing material; and introducing at least one workfunction altering metal impurity into said metal-containing material, wherein said at least one workfunction altering metal impurity is introduced during forming of a metal impurity containing layer or after formation of a layer containing said metal-containing material, and said introducing is selected from (i) codepositing the at least one workfunction altering metal impurity and the metal-containing material, (ii) forming a first layer of the metal-containing material, forming a layer containing the metal impurities on said first layer, and forming a second layer of the metal-containing material, and (iii) forming a material layer containing the metal impurities below and/or above the metal-containing material, and subjecting the material stack to a thermal process, and with the proviso that when an n-type workfunction is required, the at least one workfunction altering metal impurity comprises at least one element from Groups IIIB, IVB, or VB of the Periodic Table of Elements, and when a p-type workfunction is required the at least one workfunction altering metal impurity comprises at least one element from VIB, VIIB or VIII of the Periodic Table of Elements.