It is very frustrating (and often very expensive) to buy a device only to have it to fail with time. However, all devices (from integrated circuits to automobile tires) are fabricated from materials that will tend to degrade with time. The materials degradation will continue until some critical device parameter can no longer meet the required specification for proper device functionality. At this point, one usually says: the device has failed. This failure could be due to an increase in capacitor leakage (in the case of the integrated circuits) or the inability of an automobile tire to hold proper pressure (blowout). Materials degradation and eventual device failure are the subjects of reliability physics and engineering. Reliability physics is normally associated with understanding the kinetics of failure mechanisms. Reliability engineering is usually associated with establishing: proper design rules, robust materials selection criteria, and good manufacturing guidelines for reliable device fabrication and use.