A transistor device including a substrate, a gate structure, a first doped region, a second doped region and a body region is provided. The gate structure is disposed on the substrate. The first doped region and the second doped region are respectively disposed in the substrate at one side and another side of the gate structure. The first doped region and the second doped region have a first conductive type. The body region is disposed in the substrate at one side of the first doped region away from the gate structure. The body region has a second conductive type. The body region and the first doped region are separated by a distance, and no isolation structure exists between the body region and the first doped region.