Sub-50-nm Asymmetric Graded Low Doped Drain (AGLDD) Vertical Channel nMOSFET

40-nm and 32-nm channel length vertical nMOSFETs with an asymmetric graded low doped drain (AGLDD) structure (the LDD region only on the drain side) were experimentally demonstrated. Due to remarkably reduced peak electric field near the drain junction compared with conventional LDD structure, the vertical AGLDD structure can reduce the off-state leakage current and suppress the short channel effects dramatically. The fabricated device with 32-nm channel length, 4.0-nm gate oxide thickness still shows excellent short channel performance as the off-state leakage current (Ioff) and the ratio of the on-state driving current (Ion) to Ioffare 3.7 X 10^-11μA/μm and 2.1 X 10⁶, respectively.