A semiconductor device includes a pillar-shaped silicon layer and a first-conductivity-type diffusion layer in an upper portion of the pillar-shaped silicon layer. A sidewall having a laminated structure including an insulating film and polysilicon resides on an upper sidewall of the pillar-shaped silicon layer. A top of the polysilicon of the sidewall is electrically connected to a top of the first-conductivity-type diffusion layer and has the same conductivity as the diffusion layer.