The typical uniform rectangular beam produced by excimer laser is attractive for surface treatment. These process are developed for to change crystalline structure, surface morphology and chemical composition by doping or to remove a contamination layer. The simple modeling of mono-dimensional heat flow equation is often used to describe these processes. Depending on the deposited laser power density, different physical and chemical processes occur, from transformation in solid or liquid phase to vapor production and plasma formation. Below laser ablation fluence, the crystalline and chemical surface modifications of polymer surface are achieved for metallization and treatment on silicon surfaces are carried out for microelectronics applications and thin film transistor devices. Over laser ablation threshold, a plasma is created in the vapor induced by laser-material interaction. At low presure (mbar) this plasma can transport species from target to a substrate for thin film growth. For high pressure ambient gas (1 bar) the plasma stays confined on the target surface and react. As chemical reactions occur there is a chemical composition transform of the target surface.