A semiconductor package includes a chip including a pad; a first insulation pattern on the chip and exposing the pad; a redistribution layer (RDL) on an upper surface of the first insulation pattern and connected to the pad; a second insulation pattern on the upper surface of the first insulation pattern and including an opening exposing a ball land of the RDL and a patterned portion in the opening; an under bump metal (UBM) on upper surfaces of the second insulation pattern and patterned portion and filling the opening, the UBM including a first locking hole exposing an edge of an upper surface of the ball land; and a conductive ball on an upper surface of the UBM and including a first locking portion in the first locking hole. The first locking hole may be about 10% to about 50% of the area of the UBM upper surface.