A semiconductor unit including a circuit board having terminal electrodes on a surface thereof and a semiconductor device having an electrode pad on a first surface, where the semiconductor device is mounted face down on the surface of the circuit board. The semiconductor device has a plurality of bumps formed on the electrode pad, for electrically connecting the electrode pad to the terminal electrodes of the circuit board. Each bump includes a first bump portion and a smaller second bump portion formed on the first bump portion, and each second bump portion has a plurality of irregularities having concave portions extending in various directions. The bonding layer is formed between the second bump portion and the terminal electrode, and includes conductive particles which along with a portion of the bonding layer enter the concave portions of the plurality of irregularities of the bumps. The terminal electrodes may also have a plurality of irregularities having concave portions extending in various directions.