The variation of saturation drain current (I d,sat), induced by the random dopant variation (RDF), has been extensively studied by a new multivariate analysis method. It was found that the variation of I d,sat is originated from V th,sat and saturation velocity (V sat), while the variation of V th,sat comes from the drain induced barrier lowering (DIBL). However, the experimental results shows that V sat dominates the variation of I d,sat. From the transport theory, V sat is further decomposed into V inj and B sat, showing that V inj is the dominant factor of I d,sat variation. The faster the V inj is, the less the I d,sat variation becomes. If one improves the injection velocity, then the variation of I d,sat can be suppressed. This has been one of the significant benefits of strained silicon technology in CMOS device scaling.