Flat-band voltage shift in metal-gate/high-k/Si stacks

In metal-gate/high-k stacks adopted by the 45 nm technology node, the flat-band voltage (V_fb) shift remains one of the most critical challenges, particularly the flat-band voltage roll-off (V_fb roll-off) phenomenon in p-channel metal-oxide-semiconductor (pMOS) devices with an ultrathin oxide layer. In this paper, recent progress on the investigation of the V_fb shift and the origin of the V_fb roll-off in the metal-gate/high-k pMOS stacks are reviewed. Methods that can alleviate the V_fb shift phenomenon are summarized and the future research trend is described.