A new concept of organic transistors that uses ion-conducting membranes as a gate insulator was demonstrated. The Naflon 115® membrane was used for fabrication of MemFETs, and for the other membranes, PVDF films were washed in chloroform to remove surface impurities, dried, and irradiated with an electron-beam. The PVDF film was sandwiched between two over-patterned aluminum plates before irradiation for the patterned membrane. The irradiated PVDF films were grafted with either styrene or VBC. The PVDF-g-PS membranes were prepared by immersing the irradiated PVDF film in a mixture of styrene and isopropanol. Afterwards the samples were washed and extracted with chloroform. The demonstration shows that MemFET can be easily integrated with a functional device using ion-conducting membranes.