In this paper, the performance of Ge2Sb2Te5 (GST) and nitrogen doped Ge2Sb2Te5 (NGST) have been investigated based on standard 40 nm complementary metal-oxide-semiconductor (CMOS) technology. It shows a larger margin (similar to 2 orders) between SET and RESET resistance distributions in NGST cells. TEM and nano scratch test were implemented to find out that NGST film shows good contact with substrate which effectively increase the convergence of device resistance distributions. NGST cells embrace a higher RESET resistance and this is benefit for widening the sensing margin. Furthermore, TEM and three-dimension finite element model are developed to explain the reason for higher RESET resistance distribution of NGST cells. (C) 2015 Elsevier Ltd. All rights reserved.