A device (10) for forming at ambient atmospheric pressure a gaseous plasma comprising active species for the treatment of a treatment region, the device (10) comprising: at least one plasma cell (12) for forming said gaseous plasma for treating the treatment region, comprising the at least one plasma cell (12): an inlet (16) to receive gas from a source and an outlet (20) to discharge active species generated in the cell； a dielectric substrate (22) enclosed around a flow path (24) for gas transported from the inlet (16) to the outlet (20)； an electrode (26) formed on or in the dielectric substrate (22) to energize gas along the flow path (24) to form active species； and a protective coating (32) made of a dielectric formed on an internal surface of the dielectric substrate (22) to protect the dielectric substrate (22) against a reaction with the active species, further comprising the device (10): a nozzle (10) 114) having a nozzle outlet (120) and a plasma chamber (121) located upstream of the nozzle outlet (120)； in which the plasma cell (12, 112) is fixed inside the nozzle (114), and in which the output of the plasma cell is configured to discharge active species generated in the plasma cell (12, 112) to the plasma chamber (121)； and a ground electrode (140) comprising a dielectric substrate (142) and an electrode (141) formed on or in the dielectric substrate (142), in which the ground electrode (140) substantially surrounds and at least overlaps partially with the at least one plasma cell (12), in which the outermost end of the ground electrode (140) is closer to the nozzle outlet (120) than to the outlet (20) of the plasma cell (12).Un dispositivo (10) para formar a una presión atmosférica ambiental un plasma gaseoso que comprende especies activas para el tratamiento de una región de tratamiento, comprendiendo el dispositivo (10): al menos una célula de plasma (12) para formar dicho plasma gaseoso para tratar la región de tratamiento, comprendiendo la al menos
