We recently reported an impressive cycling stability (over 20,000 cycles) of titanium nitride (TiN) electrodes with high specific capacitance. It is anticipated that nitrogen (beta-N) doping in the oxidized surface of TiN film plays a crucial role in charge storage mechanism and stability of this material. In this work, we offer an evidence on the effect of beta-N doping on improvement in specific capacitance of vacuum annealed TiN thin films. The annealing of the TiN films leads to the diffusion of the excess beta-N from sub-surface to oxidized TiN film surface without further oxidation of the electrode surface. We demonstrate an increase in the TiN areal capacitance upon an increase in the amount of beta-N dopant. The areal capacitance of the annealed films was enhanced by 3-fold (8.2 mF cm(-2) in K2SO4 aqueous electrolyte) without sacrificing the cycling stability of the electrodes after more than 10,000 consecutive charge/discharge cycles. (C) 2017 Elsevier B.V. All rights reserved.