US Patent 9502126 Memory system and operating method thereof

A method of operating a semiconductor memory device includes applying a read voltage to a selected word line on which a program operation is performed; applying a first pass voltage to at least one unselected word line adjacent to the selected word line; applying a second pass voltage to the at least one unselected word line when a first reference time elapses; and performing a read operation on memory cells connected to the selected word line according to the read voltage when a second reference time elapses.