A semiconductor device includes a syndrome generation circuit configured to generate a syndrome code based on data and an error correction code corresponding to the data, an error determination circuit configured to detect a 1-bit error in the data based on the syndrome code, and multi-bit error detection circuit configured to determine whether the data detected to have 1-bit error includes a multi-bit error by using an error address of the data detected to have 1-bit error and an error syndrome code of the data detected to have 1-bit error.