A novel 3-D NAND Flash memory device, VSAT (Vertical-Stacked-Array- Transistor), has successfully been achieved. The VSAT was realized through a cost-effective and straightforward process called PIPE (Planarized-Integration- on-the-same-PlanE). The VSAT combined with PIPE forms a unique 3-D vertical integration method that may be exploited for ultra-high-density Flash memory chip and Solid-State-Drive (SSD) applications. The off-current level in the polysilicon-channel transistor dramatically decreases by five orders of magnitude by using an ultra-thin body of 20nm thick and a double-gate-in-series structure. In addition, hydrogen annealing improves the subthreshold swing and the mobility of the polysilicon-channel transistor.