FILM FORMING DEVICE

A film forming device forms a thin film on a substrate by reacting reaction gases in a process vessel. Electrode portions each oriented vertically are arranged to be spaced from each other in a horizontal direction. By applying high-frequency powers having different phases to adjacent electrode portions, a strong plasma generation space is formed above the substrate placed on a mounting table, while a weak plasma generation space is formed in the gap between the electrode portions and the substrate. A first reaction gas is supplied to the strong plasma generation space and a second reaction gas that forms the thin film by reacting with the active species of the first reaction gas is supplied to the weak plasma generation space. The reaction gases in the weak plasma generation space are discharged through exhaust channels.