We present the results obtained with an extended-gate ISFET totally based on amorphous oxides (GIZO as the semicon-ductor, Ta O :SiO as the dielectric and Ta O as the sensitive layer). A full characterization of the device was performed with constant ionic strength pH buffer solutions, revealing a sensitivity of 40 mV/pH with small hysteresis, and good linearity in the pH 4–pH 10 range buffer solutions. These results clearly show that it is possible to produce room-temperature disposable and low cost bio-sensors.