SEMICONDUCTOR DEVICE AND ITS MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To suppress the misfit transposition caused by the stress accompanying the difference of thermal expansion coefficient between a base layer and a foundation, in the case of using the epitaxial mixed crystal layer of silicon germanium for the base layer of a bipolar transistor. SOLUTION: An n+ collector region 2, an n- epitaxial layer 3, an element isolating oxide silicon film 4, a silicon oxide film 5, etc., are formed on a p-type silicon substrate 1, and then a silicon nitride film 51 through low-pressure CVD technique to serve as a stress relaxing layer is made. Subsequently, the silicon nitride film 51 is opened, with a CVD oxide silicon film as a mask, and further the silicon oxide film 5 is opened, using dilute fluoric acid aqueous solution; and at the same time, the removal of the CVD oxide silicon film used as a mask of the silicon nitride film 51 is performed. Then, an epitaxial mixed crystal layer of SiGe is formed by the same method as a conventional example, and further the electrodes of a base, an emitter, and a collector are formed.