Vertically-stacked double-gate nanowire FETs with controllable polarity: From devices to regular ASICs

Vertically stacked nanowire FETs (NWFETs) with gate-all-around structure are the natural and most advanced extension of FinFETs. At advanced technology nodes, many devices exhibit ambipolar behavior, i.e., the device shows n- and p-type characteristics simultaneously. In this paper, we show that, by engineering of the contacts and by constructing independent double-gate structures, the device polarity can be electrostatically programmed to be either n- or p-type. Such a device enables a compact realization of XOR-based logic functions at the cost of a denser interconnect. To mitigate the added area/routing overhead caused by the additional gate, an approach for designing an efficient regular layout, called Sea-of-Tiles is presented. Then, specific logic synthesis techniques, supporting the higher expressive power provided by this technology, are introduced and used to showcase the performance of the controllable-polarity NWFETs circuits in comparison with traditional CMOS circuits.