A data input buffer in a semiconductor is capable of avoiding operation speed deterioration of the data input buffer due to the temperature condition or process characteristic. The data input buffer in a semiconductor device includes an input detecting unit for detecting logic level of input data by comparing the voltage level of the input data with a reference voltage, a current driving capability adjusting unit for adjusting current driving capability of the input detecting unit based on at least one of temperature condition and process characteristic, and a buffering unit for buffering the output signal from the input detecting unit.