An integrated semiconductor chip or a system-on-a-chip is only as reliable as the weakest component of the entire chip. A failure occurs when the functionality of a circuit is compromised, or a bit is incorrectly read or written to a memory block. Failures are categorized as either hard or soft. Soft failures are nonpermanent failures due to temporal noise or energetic particles such as α particles or cosmic rays . On the other hand, hard failures are permanent circuit failures resulting from wear-out-induced generation of either an electrical short or open circuit or the creation of a timing error due to electrical parameter drift. Hard reliability failures come in two flavors: front of the line (FEOL) or back end of line (BEOL). FEOL encompasses all failures directly related to the transistor, while BEOL generally involves failures in the wiring including electromigration and dielectric breakdown within or between metal wiring levels. Estimating the lifetime of a chip is a time-consuming affair that often spans the entire research and development cycle of a technology node, which lasts several years. In this chapter, we will exclusively examine FEOL hard reliability failures.