The effectiveness of thermal chemical-vapor-deposited (CVD) manganese oxide (MnOx) for their application in the copper (Cu)-through-silicon-via (TSV) structure as a barrier layer was investigated by X-ray photo-electron spectroscopy (XPS), transmission electron spectroscopy (TEM), and capacitance-voltage (C-V) measurements. TEM data revealed the conformal growth of 20 nm-thick MnOx on the surface of plasma-TEOS SiO2 in the sidewall of TSV by thermal CVD. An excellent barrier property for MnOx over the thermal SiO2 was confirmed up to the maximum annealing temperature of 500 °C. In the case of plasma-TEOS SiO2, the barrier property was good up to 400 °C, but beyond that temperature, the barrier property was found deteriorated. On the contrary, the barrier performance of MnOx grown on the surface of ozone-TEOS SiO2 was found to be negligibly small. Even at room-temperature, we did observe the Cu2p signal emanating from MnOx/SiO2 region. Therefore, care must be taken while using either MnOx as a barrier layer upon ozone-TEOS SiO2 or ozone-TEOS SiO 2 itself as a dielectric liner in along the side wall of TSVs, before integrating them into 3D-LSIs.