Ultrathin Strained-Ge Channel P-MOSFETs With High- $K$ /Metal Gate and Sub-1-nm Equivalent Oxide Thickness

Surface-channel strained-Ge (s-Ge) p-MOSFETs with high-K/metal gate stack and ozone surface passivation are fabricated, for the first time. The channel is ultrathin (approximately 3-6 nm thick) s-Ge (approximately 2.2%, biaxial compression) epitaxially grown on a relaxed Si_0.56Ge_0.44 virtual substrate. Split capacitance-voltage measurements along with quantum-mechanical simulations demonstrate a capacitance-equivalent thickness of 1.3 nm and sub-1-nm equivalent oxide thickness. The effective hole mobility of these devices was extracted and exhibits 3× and 2.2× mobility enhancement over universal Si hole mobility, for s-Ge channel thicknesses of ~6 and ~3 nm, respectively.