a silicide defect 42 when silicide defects 42 occur over the source drain active silicon regions this suicide defect 42 may result in current leakage into the substrate wafer 26 second current leakage may also occur at the edge 43 of the shallow trench isolation sti 25 where it meets the silicon wafer 26 in theory the surface of the silicon active area or source drain area 22 and the surface of the adjacent sti 25 is perfectly flat however in practice there may be a depression at this location or the sti 25 may be weak at this abutment during the process of silicidation silicide can pool in this depression or cause u201c pull down u201d as illustrated in fig1 this effect may cause current leakage to the silicon substrate 26 in addition in theory a perfectly even and uniform layer of metals can be applied to the surface of a semiconductor device to form a perfect uniform layer of silicide in practice it can be very difficult to form a perfectly uniform layer of silicide silicide may not form evenly in very small active areas of silicon and or in small active areas of silicon between polysilicon lines called u201c canyons u201d this poor silicide formation may lead to leakage similar to those described above in.