According to example embodiments, an electronic device includes: a semiconductor layer; a graphene directly contacting a desired (and/or alternatively predetermined) area of the semiconductor layer; and a metal layer on the graphene. The desired (and/or alternatively predetermined) area of the semiconductor layer include one of: a constant doping density, a doping density that is equal to or less than 1019 cm−3, and a depletion width of less than or equal to 3 nm.