A wide range of values have been reported for the Fowler-Nordheim (F-N) parameters A and B for the tunneling emission in MOS capacitor structures. The parameters A and B are respectively the pre-exponential factor and the exponent in the F-N equation. In this study, it is shown that the oxide thickness is the most influential factor in determining the accuracy of the parameter B. The uncertainty of the oxide thickness may be responsible for the discrepancies in the reported values for B. The discrepancy in the value of A was attributed to the difference in the measurement conditions and gate oxide processing.