Stacked semiconductor device including improved lead frame arrangement

A semiconductor device comprising:

• a first semiconductor chip and a second semiconductor chip, each having a main surface of a rectangular shape and a rear surface which is opposite to said main surface, and a plurality of external terminals arranged on said main surface, said main surface having a pair of longer edges extending in a first direction and a pair of shorter edges extending in a second direction substantially perpendicular to said second direction, said plurality of external terminals extending in said first direction and being arranged at a substantially central position between said pair of shorter edges, said first and second semiconductor chips being stacked on each other in such a manner that said rear surfaces of said first and second semiconductor chips are contacted to each other;
• a plurality of first leads crossing said one of said pair of longer edges of said main surface of said first semiconductor chip, each of said first leads having a first portion disposed on said main surface of said first semiconductor chip, a second portion bending from said first portion toward said rear surface, and a third portion bending from said second portion in a direction away from an outer side of said first semiconductor chip;
• and
• a plurality of second leads crossing the other of said pair of longer edges of said main surface of said first semiconductor chip, each of said second leads having a first portion disposed on said main surface of said first semiconductor chip, a second portion bending from said first portion toward said rear surface, and a third portion bending from said second portion in a direction away from the outer side of said first semiconductor chip;
• wherein said first portions of said first and second leads are electrically connected to corresponding external terminals of said plurality of external terminals of said first semiconductor chip by first wires, respectively;
• a plurality of third leads crossing said one of said pair of longer edges of said main surface of said second semiconductor chip, each of said third leads having a first portion disposed on said main surface of said second semiconductor chip, a second portion bending from said first portion toward said rear surface, and a third portion bending from said second portion in a direction away from an outer side of said second semiconductor chip;
• a plurality of fourth leads crossing the other of said pair of longer edges of said main surface of said second semiconductor chip, each of said fourth lead having a first portion disposed on said main surface of said second semiconductor chip, a second portion bending from said first portion toward said rear surface, and a third portion beading from said second portion in a direction away from the outer side of said second semiconductor chip;
• wherein said first portions of said third and fourth leads are electrically connected to corresponding external terminals of said plurality of external terminals of said second semiconductor chip by second wires, respectively;
• and
• a resin mold sealing said first and second semiconductor chips, said first and second wires, and a portion of each of said first to fourth leads,
• wherein said plurality of first and fourth leads are electrically connected to each other at said third, portion of each of said first and fourth leads, and wherein said plurality of second and third leads are electrically connected to each other at said third portion of each of said second and third leads, and
• wherein each of said first portions of said first to fourth leads has a thickness thinner than a thickness of at least one of said second and third portions, respectively, in a thickness direction of said first and second semiconductor chips.