A low power semiconductor memory device using a power gating is disclosed. The semiconductor memory device includes a standard cell and a power gating cell. The standard cell is provided with a virtual supply voltage and a first supply voltage. The power gating cell generates the virtual supply voltage from a second supply voltage and provides the standard cell with the virtual supply voltage in response to a control signal. The virtual supply voltage and the first supply voltage are provided by a first metal layer and the second supply voltage is provided by a third metal layer. The power gating cell may include at least one slice block and isolator blocks. The respective slice block has a transistor for switching current. The isolator blocks are arranged on both sides of the slice block and insulate the slice block from outside.