Metal-gate work function Phi(m) modulation using Hf alloys was achieved by the interdiffusion of bilayer metallic films each with a thickness of less than or equal to 10 nm. For a bilayer stack comprising a Hf layer on a Ni layer, varying the Hf/Ni metal thickness ratio from 0 (single-layer Ni stack) to 1.4 achieved Phi(m) tunability from 4.74 to 4.2 eV after forming gas anneal (FGA) at 420 degrees C. Interdiffusion in Hf/Pt stack and Pt/Pt-Hf stack was also explored, and the largest Phi(m) shift of similar to 0.5 eV from single-layer Pt and Pt-Hf stack, respectively, was obtained after annealing at 700 degrees C for 30 s. The observed Phi(m) shift correlated to the extent of metal interdiffusion and was found to be strongly dependent on the metal thickness and anneal temperature. The Hf/Pt stack was further employed to demonstrate Phi(m) tunability of thin interdiffused metal layers on HfO2 and HfLaOx high-k gate dielectrics. Through process optimization, the interdiffusion of thin metallic layers allows precise dual-gate Phi(m) control for advanced transistors. (c) 2007 The Electrochemical Society.