Abstract: According to a time required for programing operation, respective chips of flash memories are divided into a first group and a second group of chips requiring a time longer than the first group for the programing operation, and a postburn-in test, a high temperature test, and a low temperature test are carried out to a plurality of chips belonging to the first group simultaneously, and to a plurality of chips belonging to the second group simultaneously.

Abstract: An improved flash EEPROM with a sense amplifier having a sensing characteristics suitable for sensing a data signal under an externally applied supply voltage Vcc in a lower range, and a sense amplifier having a sensing characteristics suitable for sensing a data signal under the supply voltage Vcc in a higher range. A Vcc level detecting device detects in which range the supply voltage Vcc is in, soasto selectively enable one of sense amplifiers. Since the data signal is amplified using the sense amplifier having the optimum sensing characteristics in accordance with the level of the supply voltage, the stored data can be accurately read.