In recent years, the fabrication of transition metal dichalcogenide (TMD) alloys is drawing attention due to their controllable bandgap. Fabrication of MoS_2(1−x)Te_2x is expected to be difficult due to its thermal instability although it shows wide tunable bandgap range. In this study, MoS_2(1−x)Te_2x fabrication is carried out by sputtering and post-deposition thermal treatment in chalcogen ambient. Films without phase separation were successfully fabricated. It was revealed that the band structure changes according to the chalcogen ratio. The valence band maximum shifted non-linearly showing bowing effect, while the conduction band minimum remained almost unchanged. It was considered that such bowing behavior of valence band minimum is attributed to the electronegativity difference between S and Te. The invariant nature of the conduction band was attributed to the fact that there is no such competition of electronegativity for the metal side whose electron orbitals mainly contribute to the conduction band formation. The maximum shift in the valence band maximum was as large as 0.5 eV. It was also revealed that suppressing the chalcogen deficiency may prevent phase separation. The wide tunability in the band structure and the possibility of realizing the uniform alloy promises the materials high applicability to different electronic devices.