A power-up signal generator uses a deep power down power-up signal, which should be in a standby state in a deep power down entry, for an initialization of other semiconductor elements in a DRAM device that operates after an internal power supply voltage is generated. The generator also uses the power-up signal, which is disabled in the deep power down entry and enabled in a deep power down exit by the internal power supply voltage. The generator may include a power-up detector for generating a power-up detection signal, a deep power down power-up signal generator for generating a deep power down power-up signal, a power-up signal generator for generating a power-up signal and a power-up controller for determining whether or not to enable the power-up signal in the deep power down entry.