This chapter introduces basic etching hardware and process technologies developed in Japan and in widespread use in production lines around the world. It discusses process technologies realized for the magnetron and the electron cyclotron resonance systems. At the other extreme of dry etching technologies, downflow etching, a process carried out using only neutral species, has been used in LSI manufacturing. Since the etching feature is usually isotropic, downflow etching is not applicable to the engraving of finer patterns. The wafers are chemically etched by transported long-lived species such as fluorine atoms. The problem of persistent resist-residue in the LSI production line often occurs. It was found to be possible to solve this resist-residue problem by a reaction of fluorine atoms with water vapor. In future LSI manufacturing, the downflow process with no radiative irradiation will be used as a damage-free surface treatment such as cleaning, because extremely clean and perfectly controlled surfaces are necessary to produce LSI devices.