A reaction tube without occurrence of crack or breakdown or a wafer boat without generation of particles is provided, such various faults being caused by the difference between the thermal expansion coefficients of a thin film and one of those quartz glass jigs. The present invention is applied to a quartz glass jig used in a thermal CVD apparatus, and is characterized in that the jig is made of transparent quartz glass material, and that the portion or portions exposed to the heat treatment space or the portions contacting with wafers are sand-blasted. The reason why transparent quartz glass is limited as the material is that, in case of transparent quartz glass, the surface hardness is more uniform in comparison to bubble-mixed or opaque quartz glass and thus a predetermined surface roughness is more effectively achieved by sand-blasting so that the faults as mentioned above due to the stress occurring in the treatment between a CVD film and one of the quartz glass jigs are effectively prevented.

A light source(10) includes a bulb (14) having a pair of outer leads (16,17) extending therefrom in parallel and sealed directly in the glass stem (22), whereby the outer leads (16,17) and the input leads in the glass stem (22) are the same. A protective shroud (30) surrounding the light source (10) may be supported by a metal member (40) welded to one of the leads between the stem (22) and the light source (10). The metal member carries a strap (43) seated in a circumferential constriction (36) of the shroud (30), which may be a commercially available glass vial. In another embodiment, horseshoe-shaped members (18,19) having mutually opposed concavities are welded to respective leads (16,17) and a shroud (30) is locally heated to form a circumferential constriction (36) which shrinks into the concavities, thereby supporting the shroud internally. Alternatively, the shroud can be shrunk directly against the pinch (15) so that it converges toward the open end (35) where it engages leads (16,17).