The present work deals with high-density integrated capacitors for output filters in future micro DC-DC converters. To reach high capacitance density, 3D structures were created in silicon with DRIE followed by MOCVD of ZrO2 (100 nm thick). The step coverage revealed two deposition regimes: a surface reaction controlled regime for cavities aspect ratio lower than 2 and a diffusion controlled regime for higher aspect ratios. The ZrO2 films present mostly a cubic/tetragonal structure. The permittivity extracted from the measurement is close to 27. These results are discussed with static dielectric responses calculated in literature.