DC breakdown properties of gate oxide in MOSFET

In order to investigate DC (forward-reverse) breakdown properties of gate oxide in MOSFET, two kinds of specimens are manufactured as follows: specimens with thickness of 600 /spl Aring/ and resistivities of 1.2 to 1.8 /spl Omega/cm; and specimens with thickness of 800 /spl Aring/ and diffusion times of 110 or 150 min. At the DC dielectric strength for each resistivity, it is confirmed that most of the leakage current and breakdown current flows through the n/sup +/ source when positive bias is applied but the p region when negative bias is applied. It is thought that dielectric strength due to the diffusion time results from increasing p region.