Anomalous Substrate Current in Metal-Oxide-Semiconductor Field-Effect Transistors with Large Channel Width

Anomalously large substrate current has been observed in a metal-oxide-semiconductor field-effect transistor (MOSFET) with a large channel width of 1600 mu m. The magnitude of the substrate current per unit channel width is approximately 2 orders larger than that of a MOSFET with a channel width of 100 mu m when they are compared at the maxima. Furthermore, the substrate current measured as a function of gate voltage could not be fit to a typical simulation model based on the conventional theory of impact ionization. In addition to the substrate current, anomalies were also observed in the drain current and the gate leakage current measured simultaneously with the substrate current. To explain the interrelation of the anomalous phenomena, we have introduced a hypothesis in which two modes of impact ionization are excited in the respective voltage regions generating electron-hole pairs in specific directions. (C) 2010 The Japan Society of Applied Physics