A method for producing an electronic component device, comprising: a process for individually preparing a first component on which a first conductor film containing a first high melting point metal is formed and a second component on which a second conductor film containing a second high melting point metal is formed, wherein the first high melting point metal and the second high melting point metal are the same; a low melting point metal layer forming process for forming, on at least one of the first and second conductor films (13,14), a first low melting point metal layer containing a low melting point metal having a melting point lower than that of the first and second high melting point metals; and a high melting point metal layer forming process for forming a high melting point metal layer containing the same high melting point metal as the first and second high melting point metals in such a manner as to contact the low melting point metal layer, the low melting point metal layer forming process further including a process for forming a second low melting point metal layer in such a manner that the high melting point metal layer is sandwiched between the low melting point metal layers (16,18) in the thickness direction, and a heat bonding process for, while the first conductor film and the second conductor film are made to face each other with the low melting point metal layers (16, 18) being interposed therebetween, performing heating at a temperature between the melting points of the first and second high melting point metals and the melting point of the low melting point metal to form an intermetallic compounds of the first and second high melting point metals and the low melting point metals, thereby forming a bonding portion where the first conductor film and the second conductor film are bonded to each other, wherein the high melting point metal contains Cu as the main component, the low melting point metal contains Sn as the main component, and the intermetallic compound formed between the first conductor film and the high melting point layer and the intermetallic compound formed between the second conductor film and the high melting point layer, are Cu 3 Sn; and wherein the high melting point metal layer formed in the high melting point metal layer forming process has a sufficient thickness such that the high melting point metal is supplied in an amount larger than the amount consumed for the formation of the intermetallic compounds, and the heat bonding process being carried out so that intermetallic compounds of Cu 3 Sn are generated and compounds of CU 6 Sn 5 are prevented, while leaving a part of the high melting point metal layer at the bonding portion. a process for individually preparing a first component on which a first conductor film containing a first high melting point metal is formed and a second component on which a second conductor film containing a second high melting point metal is formed, wherein the first high melting point metal and the second high melting point metal are the same; a low melting point metal layer forming process for forming, on at least one of the first and second conductor films (13,14), a first low melting point metal layer containing a low melting point metal having a melting point lower than that of the first and second high melting point metals; and a high melting point metal layer forming process for forming a high melting point metal layer containing the same high melting point metal as the first and second high melting point metals in such a manner as to contact the low melting point metal layer, the low melting point metal layer forming process further including a process for forming a second low melting point metal layer in such a manner that the high melting point metal layer is sandwiched between the low melting point metal layers (16,18) in the thickness direction, and a heat bonding process for, while the first conductor film and the second conductor film are made to face each other with the low melting point metal layers (16, 18) being interposed therebetween, performing heating at a temperature between the melting points of the first and second high melting point metals and the melting point of the low melting point metal to form an intermetallic compounds of the first and second high melting point metals and the low melting point metals, thereby forming a bonding portion where the first conductor film and the second conductor film are bonded to each other, wherein the high melting point metal contains Cu as the main component, the low melting point metal contains Sn as the main component, and the intermetallic compound formed between the first conductor film and the high melting point layer and the intermetallic compound formed between the second conductor film and the high melting point layer, are Cu 3 Sn; and wherein the high melting point metal layer formed in the high melting point metal layer forming process has a sufficient thickness such that the high melting point metal is supplied in an amount larger than the amount consumed for the formation of the intermetallic compounds, and the heat bonding process being carried out so that intermetallic compounds of Cu 3 Sn are generated and compounds of CU 6 Sn 5 are prevented, while leaving a part of the high melting point metal layer at the bonding portion.