Reliability issues including random telegraph noise (RTN) and program disturbance in floating gate (FG) NAND strings for different junction dosages are compared. Although the initial threshold voltage (VT) distributions are similar for various source/drain (S/D) dosages, these samples exhibit different amplitudes on read current fluctuation. This current noise will induce inaccuracy in sensing level and the read margin is reduced especially for multi-level cell (MLC) operation. Moreover, the junction profile has a strong impact on program disturbance. Contrary to the behavior of global self-boosting (GSB), the VT of disturbed bits show an abnormal tail distribution under high pass gate voltage (Vpass, pgm) when junction dosage is reduced. Charge pumping technique is utilized to explore the local VT distribution around junctions. Based on our characterization results, the hot-carrier injection should be responsible for this tail distribution.