  We report here the first realization of top-down silicon nanowires (SiNW)
transduced by both junction-less field effect transistor (FET) and the
piezoresistive (PZR) effect. The suspended SiNWs are among the smallest
top-down SiNWs reported to date, featuring widths down to ~20nm. This has been
achieved thanks to a 200mm-wafer-scale, VLSI process fully amenable to
monolithic CMOS co-integration. Thanks to the very small dimensions, the
conductance of the silicon nanowire can be controlled by a nearby electrostatic
gate. Both the junction-less FET and the previously demonstrated PZR
transduction have been performed with the same SiNW. These self-transducing
schemes have shown similar signal-to-background ratios, and the PZR
transduction has exhibited a relatively higher output signal. Allan deviation
AD of the same SiNW has been measured with both schemes, and we obtain AD~20ppm
for the FET detection and AD~3ppm for the PZR detection at room temperature and
low pressure. Orders of magnitude improvements are expected from tighter
electrostatic control via changes in geometry and doping level, as well as from
CMOS integration. The compact, simple topology of these elementary SiNW
resonators opens up new paths towards ultra-dense arrays for gas and mass
sensing, time keeping or logic switching systems in SiNW-CMOS platform.
