The object of the present invention is to provide a semiconductor device, which is suitable for use to connect electric condenser microphones. A semiconductor device, comprises: a conductivity-type substrate; an epitaxial layer formed on top of the substrate; island regions separating the epitaxial layer; an input transistor formed on one of the island regions; an insulation layer covering the surface of the input transistor layer; an expansion electrode formed above the insulation layer so as to provide an electrical connection to an input terminal of the input transistor; and resistivity of the epitaxial layer formed below the expansion electrode being in a range of 10005,000 cm.