Focused Ion Beam (FIB) is used to modify a ring-oscillator circuit to enable the direct characterization of AC hot-carrier effects. Probe access to internal device nodes is necessary to find out the amount of individual device degradation resulting from AC hot-carrier stress. The circuit modification on an existing wafer by FIB enables the direct measurement of individual device in the circuit before and after AC hotcarrier stressing without resorting to new mask sets and silicon wafer processing for new hotcarrier reliability test circuits that can provide realistic stress voltage waveform. Small pads produced by FIB have small acceptable impact on the stress waveform of the circuit and they still allow accurate measurement of the internal device nodes. FIB’s ‘cut and paste’ technique is used to form these probe pads. Some suggestions are made for the proper FIB work in this paper. The results of AC hot-carrier tests with the circuit modified by FIB are also presented with some illustrative figures.