Advances in semiconductor technology have led to impressive performance gains of VLSI circuits, in general, and microprocessors, in particular. However, smaller transistor and interconnect dimensions, lower power voltages, and higher operating frequencies have contributed to increased rates of occurrence of transient and intermittent faults. We address the impact of deep submicron technology on permanent, transient and intermittent classes of faults, and discuss the main trends in circuit dependability. Two case studies exemplify this analysis. The first one deals with intermittent faults induced by manufacturing residuals. The second case study shows that transients generated by timing violations are capable of silently corrupting data. It is concluded that the semiconductor industry is approaching a new stage in the design and manufacturing of VLSI circuits. Fault-tolerance features, specific to custom designed computers, have to be integrated into commercial-off-the-shelf (COTS) VLSI systems in the future, in order to preserve data integrity and limit the impact of transient and intermittent faults.