Wiring board, semiconductor device and method for manufacturing the same

A semiconductor device including a semiconductor element 1 having an active element region 1a, a plurality of element electrodes 2 formed on a principal face of the semiconductor element, external terminals 6 and 7 connected to one or more element electrodes via connection members 8 and 9, one or more first heat-dissipation protrusions 4 formed on the principal face of the semiconductor element, an insulation resin layer 10 covering the principal face of the semiconductor element and the first heat-dissipation protrusions, and a heat-dissipation medium 11 contacting a face of the insulation resin layer on a side opposite to a side contacting front faces of the first heat-dissipation protrusions. At least a part of the active element region is included in a region below a bottom face of the first heat-dissipation protrusion, the first heat-dissipation protrusion is not connected to the external terminal within the active element region, a thermal conductivity of the first heat-dissipation protrusion is larger than a thermal conductivity of the insulation resin layer, and a thickness of the insulation resin layer from the front face of the first heat-dissipation protrusion to the heat-dissipation medium is thinner than a thickness of the insulation resin layer from the principal face of the semiconductor element to the heat-dissipation medium. Thereby, it is possible to improve the speed of dissipating heat from the active element region of the mounted semiconductor element to the heat-dissipation medium.