A three-dimensional (3D) semiconductor device may include a stack of chips, including a master chip and one or more slave chips. I/O connections of slave chips need not be connected to channels on a motherboard, and only electrode pads of a master chip may be connected to the channels. Only the master chip may provide a load to the channels. A through-substrate via (TSV) boundary may be set on a data input path, a data output path, an address/command path, and/or a clock path of a semiconductor device in which the same type of semiconductor chips are stacked.