Organic thin film transistor nonvolatile memories (OTFT-NVMs) with polymeric electret layers have attracted research attention for the application to emerging wearable electronics. However, it is challenging to develop low-power flexible OTFT-NVMs due to the lack of candidate polymers for flexible electret and blocking dielectric layer (BDL) equipped with the thickness downscalability and sufficiently strong insulating properties. Here, this study reports a low-power, flexible OTFT-NVM fabricated with a bilayer dielectric stack composed of a 3 nm thick polymer electret layer and a high-performance BDL prepared via an initiated chemical vapor deposition process. Especially, a crosslinked poly(1,4-butanediol diacrylate) film is newly synthesized as a BDL, which shows excellent insulating properties with high breakdown field (E-break > 8 MV cm(-1) with its thickness of 21.3 nm). Coupled with a 3 nm thick polymer electret layer (poly(1,3,5-trimethy1-1,3,5-trivinyl cyclotrisiloxane)), the fabricated NVMs exhibit a tunable memory window with dramatically reduced programming/erasing voltages less than 15 V and an extrapolated retention time as long as 108 s. Moreover, the device maintains their memory performance up to 1.6% of applied tensile strain. The OTFT-NVMs with the ultrathin dielectric stack can serve as a promising dielectric for stable data storage in various future wearable electronics.