In an oxide semiconductor device including an active layer region constituted by an oxide semiconductor, stability when a stress is applied is improved. The oxide semiconductor device includes an active layer region constituted by an oxide semiconductor of indium (In), gallium (Ga), and zinc (Zn), wherein the active layer region contains an element selected from titanium (Ti), zirconium (Zr), and hafnium (Hf) that are Group 4 elements, or carbon (C), silicon (Si), germanium (Ge), and tin (Sn) that are Group 14 elements at a number density in a range of 1×1016 to 1×1020 cm−3.