A non-volatile semiconductor storage device has a plurality of memory strings with a plurality of electrically rewritable memory cells connected in series. Each of the memory strings includes: a memory columnar semiconductor extending in a direction perpendicular to a substrate; a tunnel insulation layer contacting the memory columnar semiconductor; a charge accumulation layer contacting the tunnel insulation layer and accumulating charges; a block insulation layer contacting the charge accumulation layer; and a plurality of memory conductive layers contacting the block insulation layer. The lower portion of the charge accumulation layer is covered by the tunnel insulation layer and the block insulation layer.