Gate-all-around structures having devices with source/drain-to-substrate electrical contact are described. An integrated circuit structure includes a first vertical arrangement of horizontal nanowires above a first fin. A first gate stack is over the first vertical arrangement of horizontal nanowires. A first pair of epitaxial source or drain structures is at first and second ends of the first vertical arrangement of horizontal nanowires. One or both of the first pair of epitaxial source or drain structures is directly electrically coupled to the first fin. A second vertical arrangement of horizontal nanowires is above a second fin. A second gate stack is over the second vertical arrangement of horizontal nanowires. A second pair of epitaxial source or drain structures is at first and second ends of the second vertical arrangement of horizontal nanowires. Both of the second pair of epitaxial source or drain structures is electrically isolated from the second fin.