In this paper, the scalability of dual trench epitaxial diode as the selector for phase change memory (PCM) has been analyzed. The 4 F-2 diode with active area of 0.002916 mu m(2) has been fabricated using the standard 40 nm complementary metal oxide semiconductor process. The ratio of disturbance current between neighboring bit-lines (BLs) to drive current remains at average 2.0%. By introducing boron implantation into the device substrate, the punch-through voltage between neighboring word-lines (WLs) is larger than 6 V. Moreover, owing to the optimized P region in PN junction, the 4 F-2 diode showed an excellent drive current of 431 mu A. Finally, the resistances of 4/6.5/10/30 F-2 diode array have been investigated, the series resistances of the buried N+ layer exhibited decreasing influence on drive current with the diode size scaling down. (C) 2017 Elsevier Ltd. All rights reserved.