This paper presents preliminary data on a new integrated circuit microelectronic pH sensor. The device is extremely miniaturized by the use of integrated circuit technology, and uses the intrinsic hydrogen ion selective properties of the gate insulator material. In order to make the device compatible with aqueous solution monitoring, the silicon dioxide-silicon nitride gate insulator structure is used. The integrated circuit chip was designed, processed, and packaged by a variety of techniques which protect all metal parts from the aqueous solution. Test data are reported on leakage current, sensitivity, reproducibility, linearity, stability, response time, and life. The results indicate that this type of pH sensor may have many significant advantages for biomedical research and application.