Wafer supporting jig and a decompressed gas phase growth method using such a jig

A decompressed gas-phase growth method where a gas is introduced into a reaction tube containing a wafer and the reaction tube is heated from the exterior so as to grow a thin film on the wafer and a ring-shaped jig is utilized, the method comprising rigidly fitting said ring-shaped jig to a support pillar, said jig being in the general form of a ring with a central opening and being made of heat resistive material, said ring-shaped jig having a plurality of wafer supporting projections provided on an upper surface thereof for providing a space between the ring and a supported wafer, and placing a substrate wafer vis-a-vis said supporting projections of said ring-shaped jig.