Abstract: A bi-MOS circuit is fabricated on first active regions assigned to the bipolar transistor and on second active regions assigned to the field effect transistors, and the field effect transistors are fabricated after said bipolar transistor, because a high-temperature heat treatment for an emitter diffusion destroys the impurity profiles of the source/drain regions of the field effect transistors, wherein a part of the field oxide layer between the second active regions is covered with an etching stopper layer before deposition of a thick silicon oxide layer in order to widely space the emitter region from the emitter electrode, even though the thick silicon oxide layer is removed from the field oxide layer between the second active regions for fabricating the field effect transistors, the etching stopper layer prevents the field oxide layer from the etchant, and the field oxide layer between the second active regions maintains the original thickness, thereby never allowing a parasitic MOS transistor to turn on