About 25years after inventing the laser annealing effects of ion implanted semiconductors a summary of the related physical phenomena is given. The field of application for short and selectively deposited energy pulses in controlled thermally activated processing is critically reviewed with the emphasis on electrical activation of implanted layers. Starting form the energy deposition and continuing to the excited transport phenomena a set of regimes can be described, which allows the classification of the variety of laser annealing methods and their different application. Within the scope of controlled thermally activated processes in nanometer dimensions old phenomena like phase transitions in strong non-equilibrium to create metastable states or producing dissipative structures by nonlinear coupling effects with self-organization are taken into account for device generations beyond 45nm. The challenges and disadvantages of laser annealing methods for planar semiconductor technology will be elaborated with respect to the current progress in laser development.