A semiconductor device is disclosed. The semiconductor device includes a hybrid transistor including a gate electrode, a drain material, a source material, and a channel material operatively coupled between the drain material and the source material. The source material and the drain material include a low bandgap high mobility material relative to the channel material that is high bandgap low mobility material. Memory arrays, semiconductor devices, and systems incorporating memory cells, and hybrid transistors are also disclosed, as well as related methods for forming and operating such devices.