This paper discusses the emission of both substrate and channel hot electrons from the silicon into the gate insulator of n-chan-nel IGFET’s. In each case the discussion begins with a physical model to elucidate the many parametric dependencies. The effect of changing important material and geometrical parameters as well as temperature and terminal voltages is documented with emission data. Under proper conditions the majority of emitted hot electrons are collected at the gate electrode, so that electron heating can be studied by directly ob- serving gate current. In addition, gate current is a sensitive probe of trapping effects in the gate insulator, and it is shown how these measurements can be used to deduce long-term stability in IGFET structures. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.