Structures for an extended-drain field-effect transistor and methods of forming an extended-drain field-effect transistor. A source region is coupled to a semiconductor layer, a drain region is coupled to the semiconductor layer, and a first gate structure is positioned over a channel region of the semiconductor layer. An extended drain region is positioned between the channel region and the drain region. The extended drain region includes a portion of the semiconductor layer between the first gate structure and the drain region. A second gate structure is arranged over the portion of the semiconductor layer.