A diode device and manufacturing method thereof are provided. The diode device includes a substrate, an epitaxial layer, a trench gate structure, a Schottky diode structure and a termination structure. An active region and a termination region are defined in the epitaxial layer. The Schottky diode structure and the trench gate structure are located in the active region and the termination structure is located in the termination region. The termination structure includes a termination trench formed in the epitaxial layer, a termination insulating layer, a first spacer, a second spacer and a first doped region. The termination insulating layer is conformingly formed on inner walls of the termination trench. The first and second spacers are disposed on two sidewalls of the termination trench. The first doped region formed beneath the termination trench has a conductive type reverse to that of the epitaxial layer.