A method for producing a pillar-shaped semiconductor device having a semiconductor pillar on a semiconductor substrate. A first material layer is formed surrounding the semiconductor pillar and the semiconductor substrate is etched using the first material layer as a mask to form a semiconductor-pillar base part under the semiconductor pillar that surrounds the semiconductor pillar in plan view. A second material layer is formed to cover an upper portion of the semiconductor-pillar base part and the first material layer. An oxidation-layer base part is formed at a lower portion of the semiconductor base part by oxidizing the semiconductor substrate and a lower portion of the semiconductor-pillar base part using the second material layer as an oxidation-resistant mask. The semiconductor pillar is within the oxidation-layer base part in plan view, and an upper surface of the oxidation-layer base part is lower than an upper surface of the semiconductor-pillar base part along a vertical direction.
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