The invention provides a semiconductor device and a manufacturing method thereof where mounting strength and accuracy can be improved without making processes complex. Grooves are formed on a back surface of a semiconductor substrate along a dicing line. Via holes are formed penetrating the semiconductor substrate from its back surface to pad electrodes. Embedded electrodes are then formed in the via holes, and a wiring layer connected with the embedded electrodes is formed extending to a region near a dicing line. Conductive terminals are formed at end portions of the wiring layer. Then, dicing is performed along the dicing line to complete the semiconductor device having inclined surfaces at end portions of its back surface. When the semiconductor device is connected with the circuit board by a reflow process, conductive paste having increased fluidity covers the conductive terminals and the inclined surfaces. The conductive paste having side fillets are formed on the circuit board around an outer edge of the semiconductor device.