We demonstrate a simple and an inexpensive approach for the low-temperature fabrication (< 200 degrees C) of low-voltage-operated (< 20 V), organic, pentacene-based, nonvolatile memory devices with a high-k hafnium dioxide (HfO2) main dielectric layer and a polymer electret layer. Two kinds of polymer insulators were used as the electret layer, i.e., a poly(vinylalcohol) (PVA) with strong polar groups and an amorphous poly(methyl methacrylate) (PMMA). We studied the memory characteristics of the corresponding devices, including writing and erasing process, long-term retention, and multiple continuous writing/erasing cycles' endurance testing. The memory windows in devices with PVA can be attributed to the dominant short-lifetime shallow traps located at the PVA/pentacene interface and in the pentacene film, whereas those in devices with PMMA are mainly due to the long-lifetime deep traps located in the PMMA layer. The possible sources of shallow-type and deep-type traps in the memory devices were discussed. Accordingly, the devices with the PMMA layer show superior memory characteristics, including a stable memory window of approximately 2.5 V after 20 V 1 s pulse, retaining 80% of memory windows after 10(3) s and a good endurance properties. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3532057] All rights reserved.