A semiconductor memory device and method of operating the same is disclosed. The semiconductor memory device includes an address decoder including pass transistor groups, a memory block selector coupled in common to the pass transistor groups, and a block decoding section configured to deliver an enable signal through the block word line based on a block group address. The memory block selector is configured to deliver the enable signal to a first pass transistor group selected from the pass transistor groups in response to a block select signal to activate the first pass transistor group.