A specimen preparation technique using a focused ion beam to generate cross-sectional transmission electron microscopy (TEM) samples of GaAs integrated circuits (ICs) was studied. Using a two axes tilting technique it was possible to prepare sample with minimal thickness (approximately 10 nm) to enhance spatial resolution in TEM and x-ray spectrometer analysis. This method was applied for failure analysis of degraded GaAs ICs. The interfacial microstructure between the gate metallization and the GaAs substrate, caused by high temperature operation, was also investigated