In this talk, plasma etching of Si, GaAs, and polymer will be reviewed. Depending on the applications, fast etch rate, high aspect ratio etching, and damage-free etching are required. In Si and GaAs etching, fast etch rates have been demonstrated to produce vias by etching through an entire wafer. On the other hand, for devices with nanostructures, high aspect ratio (large height and narrow width) etching is needed to minimize lateral etching. In addition, for these devices to be electrically or optically functional, surface damage due to plasma etching has to be eliminated. Additionally, to remove polymer inside nanochannels of microfluidic systems, fast lateral etching of polymer has been developed. Etch conditions that can provide the desired etch characteristics will be discussed. Finally, surface energy of various materials could be modified by exposure to reactive plasmas. Results of applying plasma surface treatment to reversal nanoimprint will be shown.