PURPOSE: To enable to obtain junction characteristic matched with an object and to flatten the surface completely by forming a junction for stopping a current separately at the lower portion of a bipolar transistor, and forming a structure such that layers of an emitter and a base are contacted with a high resistance layer.

CONSTITUTION: A laser diode A is constructed in a hetero structure of 4 layers on a P type substrate 21. An active layer 23 to become a layer for producing a guide of a laser light and a light amplifying action becomes a semiconductor layer which has narrow energy ban width and large refractive index to the laser light as compared with P type semiconductor layers 22, 27 and N tyep semiconductor layers 24, 26, 28. A semi-insulating semiconductor layer 25 of non-doped high resistance having the same composition as the layer 22 isolates the element between the diode A and two bipolar transistors B, B'. An N-P-N type bipolar transistor is formed of an N type semiconductor layer 28, a P type semiconductor layer 29 having a composition having narrower energy ban width than the layer 22, and an N type semiconductor layer 2a having an energy band width wider than the layer 29.