A semiconductor device manufacturing method may include the following processes. A semiconductor substrate is partially removed using a first insulating film having first and second portions as a mask to form first and second pillars of the semiconductor substrate. A second insulating film is formed on side surfaces of the first and second pillars. A silicon film is formed on the first and second insulating films. A first part of the silicon film, which is on upper surfaces of the first and second portions, is removed. A coating film, which covers the upper surfaces of the first and second portions, is formed over the semiconductor substrate. The coating film is partially removed to expose the first insulating film and a second part of the silicon film. The second part is on side surfaces of the first and second portions. The second part is removed by dry etching.