PURPOSE: To obtain synthesized quartz glass material which emits less impurities during use for heat treatment and is excellent in heat resistance by adding at least a specific quantity or more of aluminum and further a specific quantity or more of OH groups.

CONSTITUTION: The improvement of the heat resistance of quartz glass material by the addition of aluminum is the most remarkable when the aluminum content is 5ppm or more. The heat resistance is not improved so much when the aluminum content exceeds 20ppm. The control of impurity emission by the addition of OH groups is the most remarkable when its content exceeds 100ppm. Though the emission of impurities is controlled better with the increase in OH group content, adding too large quantity of OH groups to quartz glass alters the property of the crystal. Therefore, quartz glass containing OH group of up to 300ppm or so is preferable for practical use. Use of a jig made of the synthesized quartz glass in semiconductor heat treatment controls the deterioration of semiconductors.