A method of operating a semiconductor device, the semiconductor device includes: a memory block including a plurality of word lines; and a control logic for performing a first program operation on first memory cells corresponding to a first word line among the plurality of word lines, performing the first program operation on second memory cells corresponding to a second word line adjacent to the first word line, performing a second program operation on the first memory cells, performing a dummy program operation on third memory cells corresponding to a third word line adjacent to the second word line, and performing the second program operation on the second memory cells.