GATE ELECTRODE WITH DEPLETION SUPPRESSION AND TUNABLE WORKFUNCTION

摘要

Semiconductor device (100) performance is improved via a gate structure (120) having a tunable effective workfunction and reduced gate depletion effects. According to an example embodiment of the present invention, the design threshold voltage of a semiconductor device (100) is adjusted in a manner that includes providing a gate having a workfunction that enables operation of the semiconductor device (100) at a selected voltage. The gate is formed having two different conductive materials (130, 135) with different electric workfunctions that both significantly contribute to the overall workfunction of the gate. The relative composition, thickness, and arrangement of each of the two conductive material is selected to attain a gate electrode workfunction that is different than the workfunctions of each of the two layers and that sets the threshold voltage of the semiconductor device (100). In addition, by selecting the order of the layers, carrier depletion in the gate electrode can be avoided. The adjustability of the effective workfunction of the gate electrode can be applied to a variety of semiconductor devices, including any modern MOS transistor, providing independent adjustment of the channel doping, semiconductor alloy composition, and the threshold voltage of the device, thus enabling improved performance. The ability to reduce gate depletion effects also provides enhanced device current drive.