A semiconductor device, having a substrate including an insulating plate and a circuit board provided on a front surface of the insulating plate. The circuit board has a first disposition area and a second disposition area with a gap therebetween, and a groove portion, of which a longitudinal direction is parallel to the gap, formed in the gap. The semiconductor device further includes a first semiconductor chip and a second semiconductor chip located on the circuit board in the first disposition area and the second disposition area, respectively, and a blocking member located in the gap across the groove portion in parallel to the longitudinal direction in a plan view of the semiconductor device.