We investigated the relation between the generation leakage current and oxygen precipitation defects (OPD) and the temperature dependence of the generation leakage current and the diffusion leakage current for n(+)-p junctions fabricated on czochralski (CZ)Si wafers with different thermal histories. The generation and diffusion leakage current can be calculated from the area current component of the n(+)p junction leakage current. To separate the area current component from the n(+)-p total leakage current gate-controlled n(+)-p junction diodes with a wide range of perimeter-to-area ratios were investigated. The OPD (plate-like oxide pre cipitates and punch-our dislocations) were created inside CZ-Si wafers during both the prefabrication heat-treatments and the n(+)p junction fabrication process itself. After the electrical measurements, the size and shape of the OPD under the n(+)p junction regions were investigated by transmission electronmicroscopy observations. The density of the oxide precipitates was estimated for the surface and cleaved wafer planes from the optical observations of the samples etched in a Wright solution. The generation leakage current at room temperature was strongly affected by the density and size of the oxide precipitates. The activation energy of the generation leakage current for the sample with the highest OPD density was calculated as 0.58 eV, with the dominant generation centers positioned at the oxide precipitate/silicon interface.