US Patent 7656721 Semiconductor device

A semiconductor includes a first sensor amplifier, a second sensor amplifier, a first switch and a second switch. The first sensor amplifier is coupled between a local data line and a memory unit to amplify signals of the memory unit. The second sensor amplifier is coupled to a middle data line to amplify signals of the middle data line. The first switch is coupled between the middle data line and the local data line to equalize voltage levels between the middle data line and the local data line by turning on the first switch according to a data control signal. The second switch is coupled between the local data line and a reference voltage to equalize the local data line to the voltage level of the reference voltage by turning on the second switch according to a local data control signal.