Method for producing field effect transistor

A method for producing a field effect transistor comprising:

• depositing a positive photoresist on a surface of a semiconductor substrate;
• exposing a region of the positive photoresist opposite a gate electrode formation region of the substrate where a gate electrode is to be formed to light;
• converting the positive photoresist into a negative photoresist and developing the negative photoresist to form a photoresist pattern having an aperture opposite the gate electrode formation region of the substrate and symmetrical overhanging portions at the aperture;
• wet etching the semiconductor substrate using the photoresist pattern as a mask to form a first recess in the semiconductor substrate leaving overhanging portions of the photoresist pattern at the aperture;
• developing the photoresist pattern to increase the spacing between the overhanging portions at the aperture;
• using the photoresist pattern as a mask, wet etching the semiconductor substrate to increase the width of the first recess and to form a second recess in the first recess;
• and
• depositing a gate metal using the photoresist pattern as a mask to form a gate electrode in the second recess.