Gate-all-around integrated circuit structures having devices with channel-to-substrate electrical contact are described. For example, an integrated circuit structure includes a first vertical arrangement of horizontal nanowires above a first fin. A channel region of the first vertical arrangement of horizontal nanowires is electrically coupled to the first fin by a semiconductor material layer directly between the first vertical arrangement of horizontal nanowires and the first fin. A first gate stack is over the first vertical arrangement of horizontal nanowires. A second vertical arrangement of horizontal nanowires is above a second fin. A channel region of the second vertical arrangement of horizontal nanowires is electrically isolated from the second fin. A second gate stack is over the second vertical arrangement of horizontal nanowires.