Introduction Safe operation of next-generation sub-micron devices requires that power dissipation and signal levels be scaled accordingly. To successfully characterize these devices and semi- conductor processes, more precise and noise free low current measure- ments are needed. The Agilent 4156C precision semiconductor parameter analyzer allows you to measure down to the fA level. This application note shows how to precisely evaluate sub- threshold characteristics of a MOSFET device using the 4156C’s ultra low current measurement capability.