According to an embodiment, a capacitor includes a conductive substrate, a conductive layer and a dielectric layer. The conductive substrate has a first main surface and a second main surface. The first main surface includes sub-regions. Each sub-region is provided with recesses or projections each having a shape extending in one direction and arranged in a width direction thereof. One or more of the sub-regions and another one or more of the sub-regions are different from each other in a length direction of the recesses or protrusions. The conductive layer covers sidewalls and bottom surfaces of the recesses or sidewalls and top surfaces of the projections. The dielectric layer is interposed between the conductive substrate and the conductive layer.