The SiOx-based resistive switching memory was realized by a simple TaN/SiO2/n++ Si-substrate structure. Post-deposition annealing treatment not only reduced operational variation but also stabilized electrical reliability during repeated switching. The relationship between applied voltage polarity and reset switching parameters is investigated and may indicate that resistive switching occurs at the cathode side. Oxygen-vacancy clustering and asymmetrical thermal-dissipation of the electrodes are discussed as possible causes for the polarity dependence of reset switching parameters. Data retention in high- and low-resistance states was measured for over 104 s, indicating promising potential for future nonvolatile memory applications.