PURPOSE: To separately control the energy of a gaseous reactant and a vapor- deposition material and to form a high-quality thin film by providing an electron emitting means for ionizing the vapor-deposition material and a grid capable of passing the ionized material between a vaporization source and a counter electrode.

CONSTITUTION: The vapor-deposition material held by a resistance-heated vaporization source 11 in a vaporization source chamber 10 is heated by the source 11 and vaporized. The vaporized material is diverged and sent toward a substrate to be treated. The vapor-deposition material collides with the thermoelectron emitted from a thermoelectron generating filament 12 and is partly positively ionized. The ionized material passes through the grid 13, collides with the moving thermoelectron in the vicinity of the grid 13 and is further ionized. The positively ionized material is accelerated toward a substrate holder 8 negatively charged with respect to the grid 13, allowed to collide with the substrate at a high velocity and deposited. Meanwhile, the thermoelectron generated from the filament 12 is caught in the vicinity of the grid 3 and does not reach the treated substrate.