A semiconductor device includes: a cell gate trench with a bottom face and first/second side faces; a field-shield gate trench narrower than the cell gate trench; a first upper diffusion layer between the cell gate trench and the field-shield gate trench; a second upper diffusion layer on the opposite side of the cell gate trench from the first upper diffusion layer; a third upper diffusion layer on the opposite side of the field-shield gate trench from the first upper diffusion layer; a lower diffusion layer on the bottom face of the cell gate trench; first and second storage elements electrically connected to the first and second upper diffusion layers, respectively; a bit line electrically connected to the lower diffusion layer; a word line covering first and second side faces via a gate insulating film; and a field-shield gate electrode in the field-shield gate trench via a gate insulating film.