An insulated-gate semiconductor device includes: an n-type current spreading layer provided on an n−-type drift layer; a p+-type base region provided on the current spreading layer; an n+-type source region provided in an upper portion of the base region; an insulated-gate electrode structure provided inside a trench; a p+-type gate-bottom protection-region provided in the current spreading layer so as to be in contact with a bottom of the trench; and a p+-type base-bottom buried-region buried in the current spreading layer, having a bottom surface having the same depth as a bottom surface of the gate-bottom protection-region, wherein the base-bottom buried-region is divided into a plurality of portions in a depth direction through an n-type separation layer.