An integrated circuit containing a capacitive microphone with a back side cavity located within the substrate of the integrated circuit. Access holes may be formed through a dielectric support layer at the surface of the substrate to provide access for etchants to the substrate to form the back side cavity. The back side cavity may be etched after a fixed plate and permeable membrane of the capacitive microphone are formed by providing etchants through the permeable membrane and through the access holes to the substrate.