Interface engineering for enhanced electron mobilities in W/HfO/sub 2/ gate stacks

Electron mobilities of W/HfO/sub 2/ stacks were found to increase monotonically with annealing temperature with little (peak) or no degradation (1 MV/cm) when compared to poly-Si devices using conventional oxides. For stacks annealed at high temperature charge pumping curves indicate low interface states densities of /spl sim/5 /spl times/ 10/sup 10/ charges/cm/sup 2/. Mobility enhancement can also be attributed to a structural change in the HfO/sub 2/ gate stack rather than due to only interfacial layer re-growth.