A semiconductor device includes an epitaxial layer disposed over a semiconductor substrate, a drift region disposed in the epitaxial layer and adjacent to an upper surface of the epitaxial layer, a gate structure disposed over the epitaxial layer, a source region disposed in the epitaxial layer outside the drift region, and a drain region disposed in the drift region. The epitaxial layer and the drift region have a first conductivity type. The semiconductor device also includes a plurality of doped region pairs disposed in the drift region and arranged in a direction from the drain region toward the source region. Each of the plurality of doped region pairs includes a first doped region having a second conductivity type opposite to the first conductivity type, and a second doped region disposed over the first doped region. The second doped region has the first conductivity type.