Keywords: idealized vs. real device behavior, variability, ideal crystals and interfaces vs. real structures, defects, fundamentals of defect physics, fundamentals of chemical reactions and stochastic/deterministic modeling methods, interactions of defects with devices, important degradation phenomena: negative/positive bias temperature instability (NBTI/PBTI), hot carrier degradation, time-dependent dielectric breakdown (TDDB), noise (random telegraph noise (RTN), 1/f noise).