US Patent 7307893 Semiconductor device and method for controlling the same

A semiconductor memory device has a read ground and a write ground, these grounds being separately provided. Even when the read and verify operations are simultaneously executed, the source potential of an involved memory cell obtained at this time is equal to that obtained when either one of the read and verify operations is executed. Thus, the semiconductor memory device can perform the read operation at high speed with a sufficient operating margin regardless of whether the device is in the dual operation mode or not.