Patent ID: 8057599

Claim:
A substrate processing apparatus comprising: a reaction furnace for processing a substrate; a seal cap for sealing an opening of the reaction furnace hermetically; a cover formed by a plate-shaped member and installed within the hermetically sealed furnace so as to be separate from the seal cap so as to cover approximately the entire surface of the seal cap, the cover having a lower surface facing the seal cap and an opposite upper surface, facing the inner side of the reaction furnace; a small chamber formed by a space enclosed by the seal cap, the lower surface of the cover and the inner wall surface of the reaction furnace; a first feed opening facing the small chamber for supplying a first gas that is inert to the seal cap to the small chamber; a flow outlet formed by a clearance between the cover and the inner wall surface of the reaction furnace, for making the first gas supplied to the small chamber flow into a portion of the reaction furnace disposed above the upper surface of the cover; and a second feed opening disposed above the upper surface of the cover and further downstream of the flow of the first gas than the flow outlet, for supplying a second gas that is different from the first gas and is more active to the seal cap than the first gas into the reaction furnace wherein the first gas and the second gas are simultaneously supplied into the reaction furnace.