We have fabricated the four pn-type junction TEGs (Test Element Groups) having different structure. Those TEGs are close to the double-implanted (Di) MOSFETs, step by step from the simple pn diode. Voltage-current (V-I) characteristics of the hundred TEGs having p-well structure show similar blocking characteristics of those of simple pn diodes on the same wafer. This indicates that the p-well structure itself does not cause a significant deterioration on the blocking yield. On the other hand, the yield is significantly influenced by the annealing condition for ion-implanted layer. The oxide-related hard breakdown on the JFET region dominates the blocking yield. The reach-through breakdown of the TEGs having the n+ region within each p-well becomes largely suppressed by the high-temperature and short-time annealing.