Semiconductor devices include a channel layer on a substrate, the channel layer including a material having a lattice constant different from a lattice constant of the substrate, a first gate electrode on the channel layer, a first source region of a first conductivity type at a first side of the first gate electrode, a first body region of a second conductivity type under the first source region and contacting the first source region, a first drain region of the first conductivity type disposed at a second side of the first gate electrode, a first drift region of the first conductivity type under the first drain region and contacting the first drain region, and a first stud region in the channel layer and the first drift region. The first stud region has an impurity concentration higher than an impurity concentration of the first drift region.