Successful integration of Ion-Sensitive Field-Effect Transistor (ISFETs) along with Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) devices within a commercial Complementary Metal-Oxide-Semiconductor (CMOS) fabrication technology is demonstrated. Development of integrated ISFET sensors using standard and fully-compatible microelectronic processing and materials is possible if Metal-Insulator-Metal (MIM) structures are integrated in series to the gate of a standard MOSFET device. With the introduction of MIM structures, we are able to fabricate ISFETs’ sensitive areas as small as 200X200 µm² in size which are able to measure small quantities of electrolytic solutions with different ionic activities. By using these devices to measure the hydrogen ionic activity (pH) of buffer solutions, we notice a corresponding relationship between the pH of the solutions and the I-V characteristics of the MOSFET devices. Integrated ISFET devices have very-low power consumption so that they can be used for portable (on-field) detection applications within the biomedical area. This is important since these detectors are intended for use in mobile applications when portable medical-electronic solutions are required.