The medium field breakdown of metal oxide semiconductor capacitors due to the Czochralski silicon crystal originated defect was studied in view of statistical, electrical, and structural analyses. Detailed statistical analysis of breakdown electric field strength suggests the most probable model of defect incorporation into the gate oxide. It is inner wall oxidation of the open pit which is emerged on the wafer surface from the bulk during polishing. Precise electrical analysis was done for the local tunneling current which initiates the medium field breakdown. Phenomenological oxide defect sizes were calculated assuming the local oxide thinning model. They were the defect diameter as 5 to 50 nm and the local oxide thinning as ～25 nm. These data were confirmed by direct structural analysis using high precision defect isolation procedure followed by transmission electron microscopy. Direct observation revealed that the real defect size was ～200 nm which correlated well with other recently reported works. The real local oxide thinning, however, was not as large as phenomenological calculation. To explain these discrepancy, the poly-Si grain protrusion induced stress model was proposed.
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