Patent ID: 8575744

Claim:
A semiconductor device, comprising: a semiconductor element including a first terminal, a second terminal, a third terminal, and a fourth terminal formed on a terminal formation surface and a back terminal formed on a surface opposite to the terminal formation surface; a lead frame including a die pad having an element mount surface on which the semiconductor element is mounted and a first lead, a second lead, a third lead, a fourth lead, and a fifth lead placed parallel to one another; and a sealing member covering the semiconductor element, wherein the first lead is connected to the first terminal, the second lead is connected to the second terminal, the third lead is connected to the third terminal, the fourth lead is connected to the fourth terminal, the fifth lead is connected to the back terminal via the die pad, the first lead and the second lead are placed adjoining to each other and constitute a first lead group, the third lead and the fourth lead are placed adjoining to each other and constitute a second lead group, the spacing between the first lead group and the fifth lead, the spacing between the second lead group and the fifth lead, and the spacing between the first lead group and the second lead group are larger than the spacing between the first lead and the second lead and the spacing between the third lead and the fourth lead, the lead frame includes a first lead terminal, a second lead terminal, a third lead terminal, and a fourth lead terminal respectively provided at ends of the first lead, the second lead, the third lead, and the fourth lead closer to the die pad and a lead joint connecting the fifth lead to the die pad, the first lead terminal, the second lead terminal, the third lead terminal, the fourth lead terminal, and the lead joint are covered with the sealing member, and spacing b between a lead terminal, among the first lead terminal, the second lead terminal, the third lead terminal, and the fourth lead terminal, closest to the lead joint and the lead joint, spacing g between a lead terminal, among the first lead terminal, the second lead terminal, the third lead terminal, and the fourth lead terminal, closest to the die pad and the die pad, spacing B between a lead, among the first lead, the second lead, the third lead, and the fourth lead, closest to the fifth lead and the fifth lead satisfy expression (1): b≧B /( S 2 /S 1) and g≧B /( S 2 /S 1) (1) where S1 is a dielectric strength of the air, and S2 is a dielectric strength of the sealing member.