Disclosed are a crystallization process of an oxide semiconductor, a method of manufacturing a thin film transistor including the same, a thin film transistor, a display panel, and an electronic device. The crystallization process of an oxide semiconductor includes forming an amorphous oxide semiconductor layer on a substrate, forming a crystallization auxiliary layer including a light absorbing inorganic material on the amorphous oxide semiconductor layer, and annealing the crystallization auxiliary layer to crystallize the amorphous oxide semiconductor layer.