An integrated circuit phase changeable memory device includes an integrated circuit substrate, a first electrode on the integrated circuit substrate, and a second electrode on the integrated circuit substrate and spaced apart from the first electrode. A carbon nano tube and a phase changeable layer are serially disposed between the first and second electrodes. An insulating layer can include a contact hole and the carbon nano tube may be provided in the contact hole. Moreover, the phase changeable layer also may be provided at least partially in the contact hole. A layer also may be provided at least partially surrounding the carbon nano tube in the contact hole. Related fabrication methods also are provided.