Memory device and error control codes decoding method

A memory device and an ECC(Error Control Code) decoding method are provided to improve the decoding performance by selectively applying the hard decision decoding or the soft decision decoding. A memory device(100) comprises a memory cell array(110), a decoder(120) and a controller(130). The decoder performs the hard decision decoding of first data and produces the output data and the error information of output data. The controller determines the bit error rate of output data based on the error information. If the bit error rate is greater than the target bit error rate, the controller transmits the additional read command for the soft decision decoding to the memory cell array. The memory cell array transmits the second data to the decoder when receives the additional read command. The decoder performs the soft decision decoding of second data and updates the output data.