An object of the present invention is to provide an integrated semiconductor nonvolatile storage device that can be read at high speed and reprogrammed an increased number of times.In the case of conventional nonvolatile semiconductor storage devices having a split-gate structure, there is a tradeoff between the read current and the maximum allowable number of reprogramming operations. To overcome this problem, an integrated semiconductor nonvolatile storage device of the present invention is configured such that memory cells having different memory gate lengths are integrated on the same chip. This allows the device to be read at high speed and reprogrammed an increased number of times.