A semiconductor device comprising: a semiconductor substrate; and a pad structure comprising: a first insulating film formed on a surface of the semiconductor substrate; a first metal film formed on the first insulating film; a second insulating film formed on the first metal film; a first part of a second metal film formed on the second insulating film; a first via formed in the second insulating film to connect the first metal film and the first part of the second metal film; a third insulating film formed on the first part of the second metal film; a topmost layer metal film formed on the third insulating film; a second via formed in the third insulating film to connect the first part of the second metal film and the topmost layer metal film; a protective film formed on the topmost layer metal film and having a pad opening formed therein to expose a part of a surface of the topmost layer metal film for ball bonding using a ball bonder having a beveled corner at a tip of a capillary; and a second part of the second metal film formed under the pad opening, the first part of the second metal film having a rectangular frame shape and having an opening that is rectangular in plan view under the pad opening, in plan view, the first part of the second metal film protruding to an inner side of the pad opening by a predetermined amount of protrusion so as to overlap the pad opening, wherein a crushed ball is formed in the pad opening on the topmost layer metal film, the crushed ball having imprinted on it a trace of the beveled corner, and wherein the second part of the second metal film is absent under the trace of the beveled corner so as to avoid being held in contact with the first part of the second metal film, the second part of the second metal film being rectangular or circular in plan view, wherein in plane view, the second part of the second metal film is located completely within a width of the trace of the beveled corner. a semiconductor substrate; and a pad structure comprising: a first insulating film formed on a surface of the semiconductor substrate; a first metal film formed on the first insulating film; a second insulating film formed on the first metal film; a first part of a second metal film formed on the second insulating film; a first via formed in the second insulating film to connect the first metal film and the first part of the second metal film; a third insulating film formed on the first part of the second metal film; a topmost layer metal film formed on the third insulating film; a second via formed in the third insulating film to connect the first part of the second metal film and the topmost layer metal film; a protective film formed on the topmost layer metal film and having a pad opening formed therein to expose a part of a surface of the topmost layer metal film for ball bonding using a ball bonder having a beveled corner at a tip of a capillary; and a second part of the second metal film formed under the pad opening, a first insulating film formed on a surface of the semiconductor substrate; a first metal film formed on the first insulating film; a second insulating film formed on the first metal film; a first part of a second metal film formed on the second insulating film; a first via formed in the second insulating film to connect the first metal film and the first part of the second metal film; a third insulating film formed on the first part of the second metal film; a topmost layer metal film formed on the third insulating film; a second via formed in the third insulating film to connect the first part of the second metal film and the topmost layer metal film; a protective film formed on the topmost layer metal film and having a pad opening formed therein to expose a part of a surface of the topmost layer metal film for ball bonding using a ball bonder having a beveled corner at a tip of a capillary; and a second part of the second metal film formed under the pad opening, the first part of the second metal film having a rectangular frame shape and having an opening that is rectangular in plan view under the pad opening, in plan view, the first part of the second metal film protruding to an inner side of the pad opening by a predetermined amount of protrusion so as to overlap the pad opening, wherein a crushed ball is formed in the pad opening on the topmost layer metal film, the crushed ball having imprinted on it a trace of the beveled corner, and wherein the second part of the second metal film is absent under the trace of the beveled corner so as to avoid being held in contact with the first part of the second metal film, the second part of the second metal film being rectangular or circular in plan view, wherein in plane view, the second part of the second metal film is located completely within a width of the trace of the beveled corner.