a method is provided for fabricating a transistor . the transistor includes a silicon layer including a source region and a drain region , a gate stack disposed on the silicon layer between the source region and the drain region , and a sidewall spacer disposed on sidewalls of the gate stack . the gate stack includes a first layer of high dielectric constant material , a second layer comprising a metal or metal alloy , and a third layer comprising silicon or polysilicon . the sidewall spacer includes a high dielectric constant material and covers the sidewalls of at least the second and third layers of the gate stack . also provided is a method for fabricating such a transistor .