In this chapter the historical evolution over more than 30 years of pulsed laser annealing for semiconductor processing has been reviewed. After describing the main physical aspects of the laser annealing process, some of the more relevant key technologies, i.e., excimer lasers and optical systems to manipulate the laser beam, are discussed. The chapter is then focused on two major applications of semiconductor industry: the first dealing with the amorphous silicon transformation into polycrystalline silicon for the thin-film transistor (TFT) technology and the second aiming to the dopant activation in CMOS technology for both logic and power MOS applications. In the case of polysilicon technology, the advantages offered by excimer laser annealing have guaranteed the establishment of industrial production of displays based on polysilicon TFTs active matrix. In the case of CMOS applications, excimer laser …