To provide a semiconductor substrate whose step coverage and film quality and improved without rib-like unevenness of film.

At least two kinds of reactive gases are supplied onto a wafer W removing in the predetermined direction from gas heads means 52, 53 positioned above, thereby, a thin film is formed on the wafer W by a chemical vapor deposition method. The gas heads means are equipped with the fixed gas head 53 attached to the predetermined position and the moving gas head 52 which is removable in the direction right to the direction of the removing wafer W. The wafer W stops when the wafer W reaches just under the moving gas head 52, and the moving gas head 52 starts to move in the right direction, the wafer W stops when the whole wafer W moves a distance scanned by the reactive gases, then, the wafer W again removes in the predetermined direction.