When connecting a semiconductor device such as an IC chip with a circuit board by the flip-chip method, a semiconductor device is provided without forming bumps thereon, which enables highly reliable and low cost connection between the IC chip and circuit board while ensuring suppressing short-circuiting, lowering connection costs, suppressing stress concentrations at the joints and reducing damage of the IC chip or circuit board. The bumpless semiconductor device is provided with electrode pads 2 on the surface thereof and with a passivation film 3 at the periphery of the electrode pads 2, and conductive particles 4 are metallically bonded to the electric pads 2. Composite particles in which a metallic plating layer is formed at the surface of resin particles are employed as the conductive particles 4. This bumpless semiconductor device can be manufactured by (a) causing conductive particles to be electrostatically adsorbed onto one face of a flat plate; and (b) overlaying the surface of the plate having the adsorbed conductive particles on the surface of electrode pads of a bumpless semiconductor device which is provided with the electrode pads on the surface thereof and with a passivation film at the periphery of the electrode pads, and ultrasonically welding this assembly, so that the conductive particles are metallically bonded and transferred from the flat plate to the electrode pads.