In this paper, single-electron effects are firstly evidenced on nanoscale floating-gate memory devices and their impact on some electrical characteristics is studied. During this work, these phenomena have been put in evidence as well as oil transfer characteristics than on I-D-time measurements for a wide range of device area. After showing that the amplitude of discrete threshold voltage shifts due to single-electron transfer (delta V-TH) is inversely proportional to the device area, the impact of these phenomena on retention characteristics has been quantified and discussed for ultra-scaled memory devices, with dimensions reduced to 40 x 30 nm(2). It is shown that the intrinsic reliability of these devices is affected by the stochastic nature of sin.-le-electron transfer. (c) 2005 Elsevier Ltd. All rights reserved.