We investigated the effects of electron-beam-irradiation (EBI) on amorphous indium gallium zinc oxide (IGZO) films deposited by RF magnetron sputtering. The device performance of thin film transistors (TFTs) fabricated from these films was also evaluated. We conducted transmission electron microscopy and x-ray photoelectron spectroscopy to analyze the microstructure and chemical state of the synthesized IGZO. The EBI-treated IGZO TFTs achieved higher carrier mobility and on/off ratio than conventionally annealed IGZO TFTs. In addition, we found that a dual-channel structure shows electrical characteristics superior to those of a single-channel structure, with a carrier mobility of 18.1 cm 2/V· s.