70 nm Damascene-Gate MOSFETs with Minimal Polysilicon Gate-Depletion

In this work, for the first time, we present very high performance CMOS devices with 70 nm gate length and 2.2 nm Tinv effective gate oxide thickness fabricated using a damascene-gate process. Poly-Si gate electrodes are used with minimal poly depletion due to the de-coupling of the gate implantation from the source and drain implantation in the damascene-gate process. Saturation transconductance of 722 μS/μm for nMOSFETs and 354 μS/μm for pMOSFETS are achieved. ION for a 1.5 V supply is 0.9 mA/um for the nMOSFETs and 0.43 mA/um for the pMOSFETs with IOFF of both devices is 20 nA/um. The reduced junction capacitance and minimal poly-Si gate depletion in the damascene process resulted in a measured delay per stage of 8.6 ps for a 101-stage CMOS inverter ring oscillator at 1.5 V supply.