To reduce number of photolithographic processes when a BiCMOS is manufactured, by forming a part of collector by using a mask for forming a base region, and forming a remaining part of the collector by using a mask for forming a well region.

A first mask pattern 14 is formed which exposes three active regions in the center of a bipolar transistor region B, a first buried layer 15 is formed in the exposed region by ion-implanting n-type impurities, and a second buried layer 16 is formed by ion-implanting p-type impurities by using the same mask 14. The first buried layer 15 becomes a part of collector region of the bipolar transistor and the second buried layer 16 becomes a base region. Next, the first mask pattern 14 is removed and a second mask pattern 17 is formed which exposes two active regions of a first active region and the region B, and an N well region 18a and a part of collector region 18B are formed by an ion implantation.