Abstract: A method and resulting structure for a relative humidity monitor which can be built into an integrated circuit chip. A small area on a silicon chip is made porous by anodic etching. This region is then oxidized and a metal counter electrode is deposited over part of the porous area. The surface area in the dielectric under the counter electrode is very high and because of the openness of the structure, ambient moisture can quickly diffuse into the dielectric under the electrode and adsorb onto the silicon dioxide surface. Changes in ambient humidity will then be reflected by measurable changes in capacitance or conductance of the device.