We demonstrate for the first time that the use of an anti-ferroelectric film for the blocking layer of a charge trap flash (CTF) device significantly improves memory performance. The CTF device with the anti-ferroelectric blocking layer shows a larger program window and a faster program/erase speed without degradation of the retention and endurance characteristics, compared to the conventional CTF device with a typical high-k dielectric blocking layer. It is found that a capacitance boosting effect by the anti-ferroelectric layer is the origin of the performance enhancement.