A semiconductor device includes a cell region including memory cells that have a selection element and a data storage element, and a driving circuit region including a driving transistor configured to operate the selection element. The driving transistor includes active portions defined by a device isolation pattern in a substrate and a gate electrode running across the active portion along a first direction, the gate electrode including channel portions of a ring-shaped structure. The driving transistor further includes first impurity doped regions disposed in the active portions that are surrounded by channel portions, and second impurity doped regions disposed in the active portion that are separated from the first impurity doped regions by the channel portions.