We develop an HfO₂-based reversible single-domain ferroelectric (RSFE) film by coupling the flexoelectric and surface effects to stabilize the NC effect. Moreover, we demonstrate the negative capacitance-flash (NC-flash) device by integrating a blocking layer composed of RSFE/dielectric heterostructure where the NC effect is stabilized. Furthermore, we apply an AND flash-like array and source-follower/charge-sharing VMM-operation to the NC-flash for in-memory computing.