In this study, we demonstrate the abruptly steep-switching characteristics of a feedback field-effect transistor (FBFET) with a channel consisting of a p(+)-i-n(+) Si nanowire (NW) and charge spacers of discrete nanocrystals on a plastic substrate. The NW FBFET shows superior switching characteristics such as an on/off current ratio of ∼10(5) and an average subthreshold swing (SS) of 30.2 mV/dec at room temperature. Moreover, the average SS and threshold voltage values can be adjusted by programming. These sharp switching characteristics originate from a positive feedback loop generated by potential barriers in the intrinsic channel area. This paper describes in detail the switching mechanism of our device.