In order to apply two-dimensional electron-gas-field-effect-transistors (2DEG-FETs) for cell-viability sensors, we investigated the chemical/ electrical properties of TiO2 thin films (13-17 nm) prepared with the sol-gel technique on the gate surface of AlGaAs/GaAs 2DEG-FETs. Photochemical/electrochemical reactions on GaAs surface in electrolytes, which induce the degradation of 2DEG-FET performance, are effectively suppressed by introducing a TiO2 thin film on the gate area of 2DEG-FETs. Compared to conventional ion-selective FETs (ISFETs), the TiO2/2DEG-FETs in this study exhibit a high sensitivity (410 mV/mM) for H2O2 detection. TiO2 surfaces show better biocompatibility than GaAs surfaces as demonstrated by direct cell culture on these surfaces. (C) 2007 Elsevier B.V All rights reserved.