Metal-oxide-semiconductor (MOS) –eld-effect transistors (FETs), also called insulated-gate FETs (IGFETs or MOSFETs), are commonly used as electrical sensors. Complementary-MOS (CMOS), which includes both p-type and n-type semiconductors, is the dominant electronic device technology of our epoch. It promises to provide inexpensive large arrays of electrical sensors integrated with electronic buffers, ampli–ers, analog/digital conversion, and other signal processing components, coupled with array element sequencing [1]. Error detection, data analysis, and special output circuits are also feasible. It allows the integration of heating and temperature sensor elements and, increasingly, CMOS fabrication facilities are implementing processes to integrate MEMS (microelectro-mechanical systems), structures that can facilitate sample processing and applications of £uids to the sensor array. Although Si is the dominant semiconductor, as device dimensions shrink, others such as Ge and III-V compounds are being integrated.