OXIDIZING AND DIFFUSING DEVICE

PURPOSE:To prevent the intrusion of a contaminate, and to improve the controllability of the distribution of the thickness of a film by forming a cap section for a reaction tube in double tube structure and setting the pressure of the internal space of an external cap section at pressure higher than pressure in a reaction chamber for the reaction tube. CONSTITUTION:An external cap section 21 made of quartz glass is mounted in a shape that the outside section of a cap 14 section for a reaction tube 11 is covered under a sealed state through a proper space. The section 21 consists of a cap proper 22 and an external cap 23. The pressure PA' of an internal space 21a is kept at pressure slightly higher than atmospheric pressure PA. Pressure PR in a reaction chamber 11a is kept at pressure slightly lower than pressure PA' in the space 21a. Accordingly, an oxide film formed on a wafer 15 is not contaminated, and the excellent film is obtained.