Multiple threshold voltage transistor implemented by a damascene process

摘要

An ultra-large-scale integrated (ULSI) circuit includes MOSFETs which have different threshold voltages and yet have the same channel characteristics. The MOSFETs include gate structures with a polysilicon material. The polysilicon material is implanted with lower concentrations of germanium where lower threshold voltage MOSFETs are required. Over a range of 0-60% concentration of germanium, the threshold voltage can be varied by roughly 240 mV. A damascene process can be utilized to fabricate the MOSFETs.