In the Semiconductor I/C industry, it has been well documented that the proportion of factory and customer field returns attributed to device damage resulting from electrical over-stress (EOS) and electro-static discharge (ESD) can amount to 40 to 50%. This study entailed EOS and ESD simulation using a variety of models, namely the Human Body Model (HBM), the Charged Device Model (CDM) and the so-called Machine Model (MM), and then conducting electrical and physical failure analysis and comparing the results with documented analyses performed on customer field returns and factory failures. It is shown that a distinction can be made between EOS and ESD failures and between the characteristic failure signatures produced by the ESD models. The CDM physical failure location is at the input buffer and in the gate oxide, where as both HBM and MM failures occur mostly in the contacts at the input protection structures.