SEMICONDUCTOR DEVICE

A semiconductor device (10, 20) includes: a data sampler configured to receive a data signal having a first frequency and to sample the data signal with a clock signal having a second frequency, higher than the first frequency, to output data for a time corresponding to a unit interval of the data signal; an error sampler configured to sample the data signal with an error clock signal having the second frequency and a phase, different from a phase of the clock signal, to output a plurality of pieces of error data for the time corresponding to the unit interval; and an eye-opening monitor (EOM) circuit configured to compare the data with each of the plurality of pieces of error data to obtain an eye diagram of the data signal in the unit interval.