In a nonvolatile semiconductor memory system comprising a memory chip and a batttery for driving the memory chip, the memory chip includes a memory-cell matrix, a row decoder, a first level-shifting circuit for shifting the level of the output of the row decoder, a column-selecting circuit, a column decoder, a second level-shifting circuit for shifting the level of the output of the column decoder, a sense amplifier, a third level-shifting circuit for shifting the level of the data which is to be written into the memory-cell matrix, a voltage-booster circuit, a timer circuit, and an oscillator circuit. The nonvolatile semiconductor memory system operates stably when driven by a low voltage or by a voltage over a broad range.