Amorphous indium–gallium–zinc-oxide (a-IGZO) is an n-type semiconductor widely used in transparent electronic devices [1,2,3]. Due to its suitable properties like ~3 eV band gap, high charge mobility and good chemical stability this material is considered to be the lower-cost alternative for LTPS (low-temperature polysilicon) in high-pixel-density displays. The IGZO-based transistors are slightly photo-sensitive in visible domain. Their photosensitivity is boosted in ultra-violet (photon energy above 3 eV) range. This propriety is explored in this work in order to emphasize the photoconductivity of the IGZO semiconductor. IGZO thin films were fabricated by radio-frequency magnetron sputtering under various deposition regimes. The sputtered IGZO thin films were integrated in micro-sized thin film field effect transistors (TFTs) with 50 nm thick SiO2 gate dielectric layers. It was observed that the TFTs electrical output can be significantly modified when the device suffers thermal annealing. The effect of structural modifications induced by such type of post-fabrication processing is thus analyzed and discussed with respect to the TFTs performance trends.