In a semiconductor device in which a plurality of wiring substrates each mounting an electronic component are stacked and sealed by a resin, the semiconductor device can be downsized, thinned, and highly reliable, and its manufacturing cost can be reduced. By using a metal paste for electrical connection between the stacked lower-layer side wiring substrate and upper-layer side wiring substrate, a connecting pitch can be smaller than that in a connecting method of using a solder ball including Cu core, and the connection at low temperature can be achieved. Also, by coating a metal paste by a print-coating method or a dispense-coating method, manufacturing steps are simplified, so that the manufacturing cost is reduced.