A semiconductor device can include a channel region with a first semiconductor material for a majority carrier in the channel region during operation (on state) of the device and a metal contact. A source/drain region can include a semiconductor material alloy including a second semiconductor material and at least one heterojunction located between the metal contact and the channel region, wherein the heterojunction forms a band-edge offset for the majority carrier that is less than or equal to about 0.2 eV.