Embodiments of the present disclosure provide semiconductor device structures having at least one T-shaped stacked nanosheet transistor to provide increased effective conductive area across the channel regions. In one embodiment, the semiconductor device structure includes a first channel layer formed of a first material, wherein the first channel layer has a first width, and a second channel layer formed of a second material different from the first material, wherein the second channel layer has a second width less than the first width, and the second channel layer is in contact with the first channel layer. The structure also includes a gate dielectric layer conformally disposed on the first channel layer and the second channel layer, and a gate electrode layer disposed on the gate dielectric layer.