Inverters and methods of manufacture thereof are disclosed. In some embodiments, an inverter includes a substrate and a first tunnel FET (TFET) disposed over the substrate. The first TFET is a first fin field effect transistor (FinFET). A second TFET is over the first TFET. The second TFET is a second FinFET. A junction isolation region is disposed between a source of the first TFET and a source of the second TFET.