Method for manufacturing semiconductor element, semiconductor element, and semiconductor device

A method for manufacturing a semiconductor element includes: a first step of forming a mask (21) having an opening (22) on a surface (11a) of a substrate (11); a second step in which a GaN layer (32), which is a first semiconductor layer, is grown by epitaxially growing a semiconductor along the mask (21) from the surface (11a) exposed by the opening (22); and a third step for growing a GaN layer (33) as a second semiconductor layer. On a surface (33a) on which the Schottky electrode (41) is provided on the opposite side from the substrate (11) in the stacking direction, the width (w2) from the end of the surface (33a) to the Schottky electrode (41) is smaller than the width (w1) of the mask (21). 半导体元件的制造方法包含：第1工序，在基板(11)的表面(11a)上形成具有开口(22)的掩模(21)；第2工序，从由开口(22)露出的表面(11a)起，使半导体沿着掩模(21)外延生长，生长作为第1半导体层的GaN层(32)；和第3工序，生长作为第2半导体层的GaN层(33)。在位于层叠方向上与基板11相反的一侧且设置肖特基电极(41)的表面(33a)，从表面(33a)的端部到肖特基电极(41)的宽度(w2)比掩模(21)的宽度(w1)小。