A silicon nanowire (SiNW), which has been named "biristor" (bistable resistor), is demonstrated for biosensor applications. The SiNW is composed of three segments: n-type (source), p-type (floating-body), and n-type (drain). Its structure is based on a metal-oxide-semiconductor field-effect transistor without a gate. The biristor uses the uncovered floating-body as a sensing site, and it is triggered by impact ionization. A charge effect arising from biomolecules influences the triggering voltage, which is a sensing metric and changes the resistance of the SiNW. The biristor can be a promising candidate for biosensors in terms of complementary metal-oxide-semiconductor compatibility, low-cost, and compact density. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789904]