Semiconductor memory device for portable computer

摘要

The device has a selection device (207) to select at least one of several cells to/from which data is to be written/read. A substrate voltage generator (204) supplies a substrate voltage to a substrate (200) when an internal current supply voltage is greater than a predetermined value and a second substrate voltage with an absolute value less than that of the first voltage, when an internal supply voltage is below the predetermined value. An Independent claim also covers a semiconductor device with a normal operation mode and a refresh mode with a mode switch over device to switch between the modes in response to an external control signal.