PURPOSE: To enable a polycrystalline silicon film uniform in thickness to be stably formed on a base by a method wherein the tip of a double-tube structure is inserted into a silicon powder layer housed in a vessel, carrier gas is supplied between an inner cylinder and an outer cylinder, and the tip is displaced following the consumption of silicon powder.

CONSTITUTION: The tip 30a of a transfer tube 30 on a vessel side is of double- tube structure, and the tip 30a is inserted into a silicon powder 6 layer. At the same time, carrier gas is supplied between an inner cylinder 31 and an outer cylinder 32 of the tip 30a of double-tube structure, and silicon powder 6 is blown up by gas pressure into plasma of high temperature. On the other hand, a case 20 is displaced upwards by the action of a spring member 22 following the consumption of silicon powder 6 in it, whereby the part of the tip 30a of the transfer tube 30 inserted into the silicon powder 6 layer can be kept nearly constant in length. By this setup, silicon powder supplied to high temperature plasma can be kept constant in volume.