Semiconductor device and method of manufacturing the same

A semiconductor device, comprising:

• a substrate;
• a plurality of stacked structures including a plurality of conductive layers and a plurality of insulating layers formed alternately with each other on the substrate, wherein each end of the plurality of stacked structures is patterned stepwise;
• and
• at least one slit separating the plurality of stacked structures from each other,
• wherein portions of the plurality of conductive layers exposed at each end of the plurality of stacked structures are defined as a plurality of pad portions, and the plurality of pad portions have a greater thickness than unexposed portions of the plurality of conductive layers.