An auxiliary device for a plasma-enhanced chemical vapor deposition (PECVD) reaction chamber and a film deposition method using the same are revealed. The auxiliary device includes a first electric field device set around an inner wall of the reaction chamber. Thus source materials or film precursors in the plasma are moved from a center toward the inner wall around the reaction chamber by electrical attraction of the first electric field device. The auxiliary device further includes a second electric field device set under a platform surface loaded with a substrate. The second electric field device makes source materials or film precursors in the plasma become attached to and deposited on a surface of the substrate owing to electrical attraction. Thereby uniformity of the film can be controlled effectively and thickness of the film can be reduced.
