Field-effect transistor (FET)-based sensors have attractive potential for fabricating miniaturized sensor arrays by semiconductor processes. In this work, a gas-sensitive FET incorporating a polyethylene glycol (PEG) film and porous Pt electrode in the gate structure is proposed. In this new type of gas-sensitive FET, the PEG layer provides a dielectric layer that interacts with gaseous molecules (i.e., a stationary phase), while the porous Pt gate electrode allows gaseous molecules to effectively access the PEG layer. Features of the response pattern, such as peak height, recovery time, and peak shape unique to the PEG-modified FET sensor, were observed when exposed to vapor of volatile organic compounds (VOCs). The sensing mechanism of the gas-sensitive FET is discussed in terms of capacitance changes of the gate structure induced by gaseous molecule adsorption onto the stationary phase. A variety of polymeric materials might be used to modify the gate, and the proposed structure shows promise as a platform for cross-reactive FET-based gas sensor arrays for pattern recognition.