A CVD reactor apparatus includes a substrate clamp for clamping a peripheral edge of the front of a substrate disposed in a CVD reactor and, dividing a space in the reactor into a first space adjacent the front of the substrate and a second space adjacent the backside of the substrate. The apparatus also includes a unit for cooling the surface temperature of an inner wall of the reactor to a temperature equal to or less than a deposition lower limit, and a unit for supplying a CVD gas to the first space adjacent the substrate front and supplying an inert gas to the second space adjacent the substrate backside at different pressures and causing a reaction at only the substrate front, a reaction gas monitor and a substrate temperature monitor.