Stacked devices and circuits formed by stacked devices are described. In accordance with some embodiments, a semiconductor post extends vertically from a substrate. A first source/drain region is in the semiconductor post. A first gate electrode layer laterally surrounds the semiconductor post and is vertically above the first source/drain region. A first gate dielectric layer is interposed between the first gate electrode layer and the semiconductor post. A second source/drain region is in the semiconductor post and is vertically above the first gate electrode layer. The second source/drain region is connected to a power supply node. A second gate electrode layer laterally surrounds the semiconductor post and is vertically above the second source/drain region. A second gate dielectric layer is interposed between the second gate electrode layer and the semiconductor post. A third source/drain region is in the semiconductor post and is vertically above the second gate electrode layer.