PURPOSE: To prevent the roughing and contamination caused by etching by a method wherein the gate electrode material, which constitutes a MOS type field effect transistor, is left on a bipolar transistor forming region.

CONSTITUTION: After a sacrificial oxide film has been formed on the surface of a substrate 1, a gate oxide film 21 is formed, and a polycrystalline silicon layer 22 is formed thereon. Then, after the impurities of n-type and the like have been doped, an alloy film, consisting of high melting point metal W and the like and Si, is deposited and a resist film 24 is formed on the n-p-n bipolar transistor forming region located on the alloy film 23, and on the gate electrode region of an n-p channel MOS field effect transistor. Using the resist film 24 as a mask, the alloy film 23 and the polycrystalline silicon layer 22 are etched, and the gate electrode of the n-p channel MOS transistor is formed. At this time, the material of the gate electrode is left on the n-p-n bipolar transistor forming region.