Patent ID: 7679173

Claim:
A semiconductor device including a DC-DC converter, comprising: a first die pad having a first lead used for inputting to the DC-DC converter; a second die pad having a second lead used for outputting of the DC-DC converter; a third die pad having a third lead; fourth leads used for supplying ground potential to the DC-DC converter; a first semiconductor chip disposed over the first die pad, the first semiconductor chip including a high side MOSFET of the DC-DC converter, the first semiconductor chip having a first gate electrode pad, a first source electrode pad, and a first drain electrode, the first drain electrode being electrically connected to the first die pad; a second semiconductor chip disposed over the second die pad, the second semiconductor chip including a low side MOSFET of the DC-DC converter, the second semiconductor chip having a second gate electrode pad, a second source electrode pad and a second drain electrode; the second drain electrode being electrically connected to the second die pad, the second semiconductor chip having a rectangular shape in plan view, with a pair of long sides and a pair of short sides; a third semiconductor chip disposed over the third die pad, the third semiconductor chip including a first driver circuit to drive the high side MOSFET and a second driver circuit to drive the low side MOSFET; a resin body covering the first, second, and third semiconductor chips, the resin body having a pair of first side surfaces opposite each other and a pair of second side surfaces opposite each other, a first metal plate which is electrically connected to the first source electrode pad of the first semiconductor chip and the second die pad; and a second metal plate which is electrically connected to the second source electrode pad of the second semiconductor chip and the fourth leads, wherein one of the fourth leads is exposed from one of the pair of the first side surfaces of the resin body, and another one of the fourth leads is exposed from one of the pair of the second side surfaces of the resin body, wherein the second metal plate is comprised of a first portion, a second portion and a third portion, wherein the first portion of the second metal plate is disposed over the second source electrode pad of the second semiconductor chip, wherein the second portion of the second metal plate is disposed so as to overlap one of the short sides of the second semiconductor chip in plan view and is electrically and mechanically connected to said one of the fourth leads, and wherein the third portion of the second metal plate is disposed so as to overlap one of the long sides of the second semiconductor chip in plan view and is electrically and mechanically connected to said another one of the fourth leads.