A semiconductor apparatus includes a back bias control block, a first back bias switching block and second back bias switching block. The back bias control block is configured to generate a first P channel control signal and a second N channel control signal. The first back bias switching block is configured to provide one of first and second high voltages as a first P channel back bias of a first circuit in response to the first P channel control signal, and to provide one of first and second low voltages as a first N channel back bias of the first circuit in response to the first N channel control signal. The second back bias switching block is configured to provide one of the first and second high voltages as a second P channel back bias of a second circuit in response to the second P channel control signal, and to provide one of the first and second low voltages as a second N channel back bias of the second circuit in response to the second N channel control signal.