Isolation schemes for gate-all-around (GAA) transistor devices are provided herein. In some cases, the isolation schemes include changing the semiconductor nanowires/nanoribbons in a targeted channel region between active or functional transistor devices to electrically isolate those active devices. The targeted channel region is referred to herein as a dummy channel region, as it is not used as an actual channel region for an active or functional transistor device. The semiconductor nanowires/nanoribbons in the dummy channel region can be changed by converting them to an electrical insulator and/or by adding dopant that is opposite in type relative to surrounding source/drain material (to create a p-n junction). The isolation schemes described herein enable neighboring active devices to retain strain in the nanowires/nanoribbons of their channel regions, thereby improving device performance.