Ion-sensitive field effect transistors (ISFET's) have many advantages than the conventional ion selective electrode. Small size, fast response and compatible with conventional IC technologies were the most important advantages. The general structure of ISFET was the same with MOSFET, but the main difference is that the metal gate in MOSFET was replaced by reference electrode/electrolyte/insulator(ionic sensor membrane) structure in ISFET. The insulator surface will suffer the change of potential as the is sample immersed into electrolyte, by which, we can measure the pH or other ionic concentration. In this thesis the amorphous lead titanate (a-PbTiO3) thin film was prepared by sol-gel method to be the sensor gate of ISFET. The lead titanate thin films were deposited on SiO2(1000Å)/p-Si substrates, and the EIS structure was obtained. The flat-band voltage(£GVBF) can be shifted by C-V measurement. The optimum conditions were found that the firing temperature was about 4000C and thin film thickness was about 0.5