MANUFACTURE OF SEMICONDUCTOR DEVICE

PURPOSE:To prevent the decrease of manufacturing yield due to irregularity of Zener withstand voltage and energy resistance of a Zener diode, by re-distributing impurities in an oxide film and the inside of a semiconductor subatrate. CONSTITUTION:An arsenic diffusion layer 2 is formed by implanting arsenic ions in an N-type semiconductor substrate 1. An oxide film 3 is formed by thermal oxidation in a steam atmosphere, and at the same time, impurities in the arsenic diffusion layer 2 is subjected to re-distribution, in the manner in which the concentration is decreased on the semiconductor substrate surface in contact with the oxide film 3. By using the oxide film 3 as a mask, boron is selectively diffused, and a base region 4 is formed. At the same time, a Zener diode is formed in the inside of the semiconductor substrate 1. An emitter region 5 is formed by diffusing arsenic by a selective diffusion method. Thereby a Zener diode can be formed in the inside of a semiconductor substrate wherein influence of defect is little.