Vertical transistor devices are described. For example, in one embodiment, a vertical transistor device includes an epitaxial source semiconductor region disposed on a substrate, an epitaxial channel semiconductor region disposed on the source semiconductor region, an epitaxial drain semiconductor region disposed on the channel semiconductor region, and a gate electrode region surrounding sidewalls of the semiconductor channel region. A composition of at least one of the semiconductor regions varies along a longitudinal axis that is perpendicular with respect to a surface of the substrate.