Semiconductor device of chip-on-chip structure, assembling process therefor, and semiconductor chip to be bonded to solid surface

A semiconductor device, comprising:

• a first semiconductor chip;
• a second semiconductor chip bonded to the first semiconductor chip in a stacked relation;
• a first bump formed on a surface of the first semiconductor chip;
• and
• a second bump formed on a surface of the second semiconductor chip;
• wherein the first and second bumps respectively have mating surfaces to be bonded to each other, and the mating surfaces of the first and second bumps having different areas.

A semiconductor device assembling process, comprising the steps of:

• forming a registration recess on a surface of a first semiconductor chip;
• forming a registration recess on a surface of a second semiconductor chip;
• placing a spherical member on the registration recess of the first semiconductor chip;
• stacking the first and second semiconductor chips with the spherical member being held between the registration recesses of the first and second semiconductor chips;
• and
• bonding the stacked first and second semiconductor chips to each other.