Thin-film transistors (TFTs) are one of the most promising practical applications of single-walled carbon nanotubes (SWNTs) due to their flexible filament-like structure and high carrier mobility [1]. For the fabrication of industrial electrical devices, it is an inevitable issue to utilize both p- and n-type transistors as basic components of the electrical circuits. Since oxygen and water molecules adsorbing on the surface of SWNTs are known to play a role as an electron acceptor against SWNTs, SWNTs–TFTs have p-type semiconducting features. To date, there are several reports on the fabrication of n-type SWNTs–TFTs by functionalizing the outside surface of SWNTs [2]. However, the operation of n-type SWNTs–TFTs is limited only under the specific condition and the fabrication of stable n-type SWNTs–TFTs under the various environmental conditions has not been realized.