Extended gate field-effect transistor (EGFET) is a device composed of a conventional ion-sensitive electrode and a MOSFET device, which can be applied to the measurement of ion content in a solution. This structure has a lot of advantages as compared to the Ion- Sensitive Field Effect Transistor (ISFET). In this work, we constructed an EGFET by connecting the sensing structure fabricated with SnO 2 to a commercial MOSFET (CD4007UB). From the numerical simulation of site binding model it is possible to determine some of the desirable characteristics of the films. We investigate and compare SnO 2 films prepared using both the Sol-gel and the Pechini methods. The aim is an amorphous material for the EGFET. The SnO 2 powder was obtained at different calcinating temperatures (200 - 500°C) and they were investigated by X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The films were investigated as pH sensors (range 2-11).3602:00:00478481Yunqing, M., Jianrong, C., Keming, F., (2005) J. Biochen. Biophys. Methods, , in pressBergveld, P., (2003) Sens. and Actuators B, 88, p. 1Chi, L.-L., Chou, J.-C., Chung, W.-Y., Sun, T.-P., Hsiung, S.-K., (2000) Materials Chemistry and Physics, 63, p. 19Schöning, M.J., Poghossian, A., (2002) The Analyst, 127, p. 1137Chou, J.-C., Wang, Y.-F., (2002) J. Appl Phys, 41, p. 5941Chou, J.-C., K., P., Chen, Z.-J., (2003) J. Appl Phys, 42, p. 6790Yates, D.E., Levine, S., Healy, T.W., (1974) J. Chem. Soc. Fraday Trans., 1Fung, C.D., Cheung, P.W., Ko, W.H., (1986) IEEE Trans. Electron Devices ED-33, 1, p. 8Antognetti, P., Massobrio, G., (1988) Semiconductor Device Modeling with SPICELiao, H.-K., Chi, L.-L., Chou, J.-C., Chung, W.-Y., Sun, T.-P., H., S.-K., (1999) Mat. Chem. and Phys., 59, p. 6Kwon, D.-H., Cho, B.-W., Kim, C.-S., Shon, B.-K., (1996) Sens, and Actuators B, 34, p. 441Liao, H.-K., Chou, J.-C., Chung, W.-Y., Sun, T.-P., Hsiung, S.-K., (2000) Sens, and Actuators B, 65, p. 23Chatelon, J.P., Terrier, C., Roger, J.A., (1997) Journal of Sol-gel Science and Technology, p. 10Rodrigues, E.C.P.E., Olivi, P., (2003) J. of Physics and Chemistry of Solids, 64, p. 1105Siciliano, P., (2000) Sensors and Actuators B, 70, p. 153