This invention relates to a gas delivery device for use in low pressure Atomic Layer Deposition at a substrate location. The device includes a first generally elongating injector (21) for supplying process gas to a process zone (22). A first exhaust zone (23) circumjacent the process zone (22); and a further injector (25) circumjacent the first exhaust zone for supplying purge or inert gas at outlet (26) surrounding the process zone (22, 24) for facing the location circumjacent the outlet to define at least a partial gas seal.
