The disclosure is directed to laser spike annealing using fiber lasers. The method includes performing laser spike annealing of a surface of a wafer by: generating with a plurality of fiber laser systems respective CW output radiation beams that partially overlap at the wafer surface to form an elongate annealing image having a long axis and a length LA along the long axis; heating at least a region of the wafer to a pre-anneal temperature TPA; and scanning the elongate annealing image over the wafer surface and within the pre-heat region so that the annealing image has a dwell time tD in the range 30 ns≦tD≦10 ms and raises the wafer surface temperature to an annealing temperature TA.