Patent ID: 8300480

Claim:
A semiconductor device comprising: a sense amplifier; a step up circuit supplied with an external power supply voltage and outputting a voltage higher than said external power supply voltage; a first step down circuit supplied with said external power supply voltage and outputting a voltage lower than said external power supply voltage; a drive signal line connected to said sense amplifier, the drive signal line supplying electric power required to operate said sense amplifier; a first line connected to an output terminal of said step up circuit; a second line connected to an output terminal of said first step down circuit; a first switch connected between said first line and said drive signal line; a second switch connected between said second line and said drive signal line; and a control circuit; wherein in a normal mode, said control circuit renders said first switch conductive for a first period in an initial stage of operation of said sense amplifier, and, after said first period, said control circuit renders said first switch nonconductive and renders said second switch conductive for a second period, operating said sense amplifier at both the voltage higher than said external power supply voltage and the voltage lower than said external power supply voltage; and in a refresh mode in at least one refreshing cycle, while said step up circuit is being shut down, said control circuit renders either one or both of said first switch and said second switch conductive for a third period longer than the sum of said first period and said second period, operating said sense amplifier at the voltage lower than said external power supply voltage.