By generating closed-loop electron E × B drift over the front and back surface of a band magnetron cathode, a uniform magnetron plasma can be formed over the front surface. Here, we attempted to generate a uniform supermagnetron plasma under a stationary magnetic field by situating two such band magnetron cathodes face-to-face in parallel. Performing uniform supermagnetron plasma chemical vapor deposition (CVD) with tetraethylorthosilicate (TEOS)/O₂ CVD, SiO₂ films with good uniformity (±5%) at the central region of the cathode could be achieved under a stationary magnetic field of about 160 G. Using this supermagnetron plasma CVD apparatus, a-CN_x:H films were then deposited to investigate their characteristics using isobutane (i-C₄H₁₀)/N₂ mixed gases. A relatively high deposition rate of about 100 nm/min was obtained. The a-CN_x:H films obtained had a hardness of about 25 GPa, higher than that of glass (22 GPa).