Nonvolatile memory device and method of programming in the same

A method of programming in a nonvolatile memory device, the nonvolatile memory device comprising a memory cell region including a first metal pad and a peripheral circuit region including a second metal pad, wherein the peripheral circuit region is vertically connected to the memory cell region by the first metal pad and the second metal pad, the method comprising:

• providing a memory block in the memory cell region comprising a plurality of stacks disposed in a vertical direction, each memory block comprising a plurality of cell strings, and each cell string comprising a plurality of memory cells connected in series in the vertical direction between a source line and each of a plurality of bitlines;
• providing a plurality of intermediate switching transistors disposed in a boundary portion between two adjacent stacks in the vertical direction, the intermediate switching transistors performing a switching operation to control electrical connection of the cell strings, respectively;
• and
• performing a boosting operation to boost voltages of channels of the stacks while controlling the switching operation of the intermediate switching transistors during a program operation with respect to the memory block,
• wherein the boosting operation is performed based on the program operation being performed with respect to a second stack, and the boosting operation is omitted based on the program operation being performed with respect to a first stack.