MANUFACTURE OF SEMICONDUCTOR DEVICE

PURPOSE:To securely prevent an emitter layer and a collector layer from being shortcircuited or leaked by forming the thickness of an end of a base layer just under a bird beak extending from interelement separation oxide film to be the same level or more as that of an intermediate part. CONSTITUTION:A base layer 18 is previously ion-implanted with the same impurity 14 as the base layer 18 at a part just under a bird beak extending from an interelement separation oxide film 12, and further a base layer 18 part is ion-implanted with an impurity 17 anew, to form the base layer 18 in a desired manner. Hereby, the thickness of an end of the base layer 18 just under the bird beak can be formed to be the same level or more as that of an intermediate layer. Thus, an emitter layer and a collector layer can be prevented from shortcircuiting or leaking with each other.