A novel silicon nanowire with programmable conductivity which utilizes sensitivity of conductance to surface charging has been investigated. The device consists of a nanowire with a width of 10-25 nm and side gates for control of surface charging on to the nanowire. The wire current measured during sweep of the side gate exhibited clear hysteresis characteristics and significant retention of the programmed states for more than 1000 s. Surface potential imaging of the nanowire by means of scanning Maxwell-stress microscopy (SMM) has been carried out for correlating the programmed conductivity to charging on the nanowire. The SMM images clearly exhibited that charging on the nanowire which provided the programmable conductivity was precisely controlled by the side gate sweep. (C) 2003 American Vacuum Society.