Abstract: An address transition detector (ATD) of a semiconductor memory device. In particular, even if the address transition of the semiconductor memory device occurs over a long time, malfunction is prevented by synchronizing outputs of a buffer and a decoder and an output of the ATD circuit. To accomplish this, input block for sensing a high trip level and a low trip level is included in the ATD circuit. Thus, if the address transition occurs slowly over a long time, the duration of a short pulse indicating the address transition becomes long, thereby producing accurate data. Moreover, since the ATD is not restricted to a particular system application, it can be used in a wide variety of applications by adapting a memory device to utilize the ATD.