Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• a monolithic silicon substrate;
• a first insulation layer formed on a front surface of the substrate;
• a pad electrode formed on the first insulation layer;
• a supporting member bonded to the front surface so as to cover the pad electrode, the substrate having a via hole formed therein and extending from a back surface of the substrate to a surface of the pad electrode;
• and
• a second insulation layer formed in the via hole,
• wherein the via hole comprises a wide portion that is closer to the front surface than to the back surface and is wider than a narrow portion of the via hole that is closer to the back surface than to the front surface,
• the first insulation layer has an opening located at the pad electrode, and the second insulation layer bends at a boundary between the substrate and the first insulation layer so as to extend into the opening to cover a side edge of the first insulation layer in the opening to prevent insulation failure in the via hole, and
• one end of the wide portion of the via hole is at a plane defined by the front surface of the substrate.