To provide a field effect transistor with a uniform gate size at low cost, wherein the transistor has a smaller gate size and higher-frequency performance than before.

When an opening for forming a gate electrode is formed by exposing a resist using a projection aligner in a process of providing the opening to form the opening, thicknesses of a source electrode and a drain electrode are set to predetermined values so as to form the resist to be exposed so that the width of the opening on a semiconductor substrate which is formed by the exposure is smaller than a luminous flux size on a wafer defined by a reticle and a reduction ratio of the aligner.