Lasers are used as a tool in many Micro System Technology production processes. This paper gives an impression of laser micro-machining in this field. Both, theoretical backgrounds and applications are discussed, with a concentration on laser processing of silicon. Different types of lasers, used for the applications mentioned in this paper, are compared with each other. These types of lasers are characterized by the pulse duration, which is respectively in the nano-, pico- and femtosecond range.