Integrated circuit devices are provide having a vertical diode therein.
The devices include an integrated circuit substrate and an insulating
layer on the integrated circuit substrate. A contact hole penetrates the
insulating layer. A vertical diode is in lower region of the contact hole
and a bottom electrode in the contact hole has a bottom surface on a top
surface of the vertical diode. The bottom electrode is self-aligned with
the vertical diode. A top surface area of the bottom electrode is less
than a horizontal section area of the contact hole. Methods of forming
the integrated circuit devices and phase change memory cells are also
provided.