The present disclosure provides a CMOS structure, including a substrate, a metallization layer over the substrate, a sensing structure over the metallization layer, and a signal transmitting structure adjacent to the sensing structure. The sensing structure includes an outgassing layer over the metallization layer, a patterned outgassing barrier over the outgassing layer; and an electrode over the patterned outgassing barrier. The signal transmitting structure electrically couples the electrode and the metallization layer.