The invention discloses a semiconductor device, which is used to inhibit large-scale, and is used to guarantee thermal capacity of heat energy generated by semiconductor element. In a semiconductor device 100, a first end of a first lead frame 151 is connected via solder 141 to a first circuit pattern 112c and another end extends outside from a case 160. In the same way, a first end of a second lead frame 152 is connected via solder 142 to a third circuit pattern 112d and another end extends outside from a case 160. Third and fourth circuit patterns 112a,112b that are covered by the first lead frame 151 are respectively buried by insulating layers 131,132. In addition, a semiconductor element 180 is provided via solder 170 on a region of the first lead frame 151 above the first circuit pattern 112c. Wires 190 electrically connect the semiconductor element 180 and a region of the second lead frame 152 above the third circuit pattern 112d.