Disclosed is a page buffer having a wired-OR type structure and a cache function which is adapted for use in a nonvolatile semiconductor memory device and a method of programming same. The page buffer embeds the cache latch block in relation to the cache function. Moreover, the nonvolatile semiconductor memory device includes an output driver enabling an internal output line to be unidirectional driven, thereby enabling a program-verifying operation using the wired-OR scheme.