Masking member for forming fine electrode and manufacturing method therefor, method for forming electrode, and field effect transistor

A fine electrode-forming masking member for forming fine gate electrodes, which can decrease gate length of a gate electrode of a field effect transistor. The method includes forming a first masking member having penetrating portions formed into opening patterns in conformity with the fine gate electrodes, on a semiconductor substrate using a photosensitive resin; and heating the first masking member so that parts of sidewalk in contact with the substrate of the penetrating portions flow along the semiconductor substrate to form extension portions. Accordingly, the widths of the penetrating portions at the bottom surface side are decreased so as to form the opening patterns. Gate electrodes are formed on regions of the semiconductor substrate exposed through the opening patterns while the substrate is masked with the fine electrode-forming masking member.