Characteristics of a band edge p-channel metal-oxide-semiconductor field effect transistors fabricated with a high-k /WAl_x/TiSiN gate stack

A metal/high-k gate stack with a p-type band edge effective work function (EWF) of about 5.0 eV is demonstrated using a thin WAl_x capping layer. The WAl_x stack exhibits a lower threshold voltage (higher flatband voltage) value and better equivalent oxide thickness scalability than previously reported high EWF gate stacks using an AlO_x cap. The WAl_x cap p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) show significantly improved negative bias temperature instability (NBTI) characteristics than AlO_x-capped pMOSFETs, which is attributed to negligible diffusion of Al into the interfacial oxide layer adjacent to the Si substrate.