A semiconductor memory device having a first memory cell array block including a memory cell having a floating body, the memory cell coupled to a word line, a first bit line, and a first source line, a second memory cell array block including a reference memory cell having a floating body, the reference memory cell coupled to a reference word line, a second bit line, and a second source line, a first isolation gate portion configured to selectively transmit a signal between the first bit line and at least one of a sense bit line and an inverted sense bit line, a second isolation gate portion configured to selectively transmit a signal between the second bit line and at least one of the sense bit lines, and a sense amplifier configured to amplify voltages of the sense bit line and the inverted sense bit line to first and second sense amplifying voltage levels.