This paper presents the impact of time dependent dielectric breakdown (TDDB, also called as gate oxide breakdown) failure on nanoscale digital CMOS Circuits. Recently, TDDB for ultra-thin gate oxides has been considered as one of the critical reliability issues which can lead to performance degradation or logic failures in nanoscale CMOS devices. Also, leakage power in the standby mode can be increased significantly. In this paper, TDDB aging effects on large CMOS digital circuits in the 45nm technology are analyzed. Simulation results show that TDDB effect on MOSFET circuits can result in more significant increase of power consumption compared to delay increase.