Stacked Ge-Nanosheet GAAFETs Fabricated by Ge/Si Multilayer Epitaxy

Horizontally stacked Ge-nanosheet gate-all-around FETs (GAAFETs) are demonstrated for the first time. The Ge/Si multilayers instead of the typically used Ge/SiGe ones were epitaxially grown as the starting material. To avoid island growth, the Ge/Si multilayers were epitaxially grown at a low temperature. Using megasonic agitation, the Si in Ge/Si multilayers can be easily etched with good selectivity using a tetramethylammonium hydroxide water solution at an appropriate temperature. Finally, the p- and n-GAAFETs of gate length ( {L}_{G}) 90 nm were fabricated, and drive currents {I}_{ \mathrm{\scriptscriptstyle ON}} of 1650 and 1510~\mu \text{A}/\mu \text{m} (per width of channel footprint) were achieved, respectively.