Chalcogenide devices are delineated and sidewalls of the devices are sealed, in an anaerobic and/or anhydrous environment environment. Throughout the delineation and sealing steps, and any intervening steps, the sidewalls are not exposed to oxygen or water. In an illustrative embodiment, a cluster tool includes an etching tool and a sealing/deposition tool configured to etch and seal the chalcogenide devices and to maintain the devices in an anaerobic and/or anhydrous environment throughout the process.