A method of producing a miniaturized, fixed volume, internal reference gas chamber comprising the pores of a porous material, suitable for use in a rapid response, highly precise, internal reference, solid electrolyte electrochemical-type oxygen sensor capable of detecting oxygen partial pressures in internal combustion engines operating within lean air/fuel mixtures is accomplished using a four step technique. A thin film layer of material is deposited onto a supporting substrate and patterned, said material comprises at least one component resistant to a subsequent removal step and at least one sacrificial component not resistant to the same subsequent removal step. The said material is then sealed everywhere except at an external orifice. The sacrificial component of said material is then decomposed and removed during a removal step, providing an interlocking network of porosity comprised within the porous component of said material. The internal reference gas chamber is positioned adjacent to the electrodes of the sense and pump cells comprised within the oxygen sensing device.