The growing field of applications of plasma as deposition, etching, surface modification and chemical conversion has stimulated a renewed interest in plasma science in the atomic physical chemistry regime. The necessity to optimize the various plasma processing techniques in terms of rates, and material properties has made it mandatory to take a new look at the various processes, as fragmentation, plasma and radical transport and plasma surface interaction with advanced diagnostics and with modelization. Many types of plasmas are used in the technology of plasma chemistry: varying from RF-glow, discharges, coronas to high density arcs. The physics involved will be illustrated at the hand of important examples: etching and modification of surfaces and the deposition of thin layers of amorphous (a-C:B, a-Si:H) and crystalline (diamond, graphite) layers. Besides dissociation and ionization in the plasma, wall association, recirculation, cluster formation and energy flows are important issues. These conclusions are also pertinent to the new field of waste destruction and are directly relevant to the economics of the plasma process.