PURPOSE: A semiconductor device is provided to improve integration by giving a chip ID to a plurality of slave chips without a one-time recording device. CONSTITUTION: A slave chip ID generating unit(200) is located in first to n-th slave chips and generates the (m+1)-th operation code by adding one to the m-th operation code. A master chip ID generating unit(100) generates a variable first operation code in response to a selection signal. N is 2 or more. M is between 1 and n. The master chip ID generating unit includes a selection unit. The selection unit generates the variable first operation code by selecting an initial code and a variable code according to the selection signal.
