This work investigates in the first place, the improvement in leakage current and breakdown field of the copper metal-insulator-semiconductor (Cu-MIS) capacitor with a plasma-enhanced chemical vapor deposited (PECVD) amorphous silicon oxycarbide (alpha-SiCO, k = 3.7) dielectric barrier. This is followed by investigating the improvement in leakage current and breakdown field of the Cu-comb capacitor with a carbon-doped low-k PECVD organosilicate glass (k = 3) as the intermetal dielectric and an alpha-SiCO dielectric film as the Cu cap barrier. The leakage current and breakdown field of Cu-MIS and Cu-comb capacitors are dependent on the species of the dielectric barrier. The Cu-MIS and Cu-comb capacitors with an alpha-SiCO dielectric barrier exhibit a leakage current at least three orders of magnitude smaller than those with an amorphous silicon carbide (alpha-SiC, k = 4.4) dielectric barrier at an applied electric field of 1.6 MV/cm between 25 and 250 degreesC. Moreover, the breakdown field of the Cu-MIS and Cu-comb capacitors with an alpha-SiCO dielectric barrier, measured at 200 degreesC, are 60 and 25%, respectively, higher than that of the capacitors with an alpha-SiC barrier. The decreased leakage current and increased breakdown field of the Cu-MIS and Cu-comb capacitors with an alpha-SiCO dielectric barrier are attributed to the higher density, oxygen-improved film property, nonsemiconductor behavior, and lower fringe- or surface-electric field of the alpha-SiCO dielectric film. (C) 2004 The Electrochemical Society.