PURPOSE: To improve the yield rate of a bipolar type semiconductor, by specifying a thickness tμm of a field oxide film and an arsenic concentration ncm-3 in a polycrystal silicon film pattern by relationship t≤-0.117×10-20n+1.42.

CONSTITUTION: An analog digital coexistence type semiconductor is manufactured by using a selective oxidation method and diffusion technology from a polycrystal silicon film pattern. At this time, relationship between a thickness (t)μm of a field oxide film and an arsenic concentration (n)cm-3 in the polycrystal silicon film pattern is specified by an expression t≤-0.117×10-20n+1.42. Furthermore, the concentration of impurities included in the pilycrystal silicon film pattern over the element region for an analog element is made higher than the concentration of impurities included in the polycrystal silicon film pattern on the element region for a digital element.