PURPOSE: To eliminate squarish parts, to and from which flakes generated in a reaction chamber adhere easily and exfoliate easily, and to prevent the flakes from concentrating and adhering on a specified part in the reaction chamber by a method wherein the forms of the squarish peripheral parts, which are located on the side of the chamber, of the semiconductor substrate entrance and the semiconductor substrate exit of the chamber are provided with a rounding or the peripheral parts are chamferred.

CONSTITUTION: When desired gas is introduced in a reaction chamber 1 and a film formation is performed on a semiconductor substrate, white flakes are generated in the camber 1. These flakes have the property of adhering normally to the squarish peripheral parts of a semiconductor substrate entrance 3 and a semiconductor substrate exit 4 of the chamber 1 mostly in a concentrated manner. There, the peripheral parts of the entrance 3 and the exit 4 of a semiconductor manufacturing device 20 are provided with a rounding. Thereby, it is eliminated that the flakes concentrate and adhere on these parts. Accordingly, it can be prevented that the flakes exfoliate from these parts and the flakes fall on the substrate at the time of the film formation.