Provided is an organic thin film transistor, method of forming the same, and a memory device employing the same. The organic thin film transistor includes a substrate, a source electrode and a drain electrode on the substrate, an active layer on the substrate between the source electrode and the drain electrode, a gate electrode controlling the active layer, and an organic dielectric layer between the active layer and the gate electrode. The organic dielectric layer includes nanoparticles, a hydrophilic polymer surrounding the nanoparticles, and a hydrophobic polymer.