Reverse leakage current
When a semiconductor device is reverse biased it should not conduct any current at all, however, due to increased barrier potential, the free electrons on p side are dragged towards positive terminal of the battery, while holes on n side are dragged towards negative terminal of the battery. This produces a current of minority charge carriers and hence its magnitude is extremely small. For constant temperature reverse current is almost constant though applied reverse voltage is increased up to certain limit. Hence it is also called as reverse saturation current.
Reverse leakage current is also known as "zero gate voltage drain current" with MOSFETs. The leakage current increased with temperature. As an example the Fairchild Semiconductor FDV303N has a reverse leakage of up to 1 microamp at room temperature rising to 10 microamp with a junction temperature of 50 degree Celsius. For all basic purposes, leakage current is very small, and, thus, is normally negligible.