A silicon carbide semiconductor element includes n-type silicon carbide epitaxial layers formed on an n+-type silicon carbide semiconductor substrate, plural p base layers selectively formed in surfaces of the silicon carbide epitaxial layers, a p-type silicon carbide epitaxial layer formed in the silicon carbide epitaxial layer, and a trench penetrating at least the silicon carbide epitaxial layer. The silicon carbide semiconductor element also includes, in a portion of the silicon carbide epitaxial layer, a mesa portion exposing the p base layer. The silicon carbide semiconductor element further includes, between consecutive mesa side faces of the mesa portion, a flat portion substantially parallel to the silicon carbide substrate. The remaining thickness of the exposed p base layer is larger than 0.5 μm and smaller than 1.0 μm.