Semiconductor device and manufacturing method thereof

A method of manufacturing a semiconductor device, having the steps of:

• (a) providing a semiconductor wafer having a plurality of chip regions and a cutting region located between the plurality of chip regions, the semiconductor wafer having a front surface and a back surface opposite the front surface,
• wherein each of the plurality of chip regions has:
• a first power transistor formation region in which a first power transistor is formed;
• and
• a second power transistor formation region in which a second power transistor reversely coupled in series to the first power transistor is formed, and
• wherein a first source of the first power transistor, a first gate of the first power transistor, a second source of the second power transistor and a second gate are respectively formed at positions closer to the front surface than the back surface;
• (b) after the step (a), forming a drain electrode embedded inside of a groove formed in the back surface of the semiconductor wafer, and electrically coupled to each of a first drain of the first power transistor and a second drain of the second power transistor;
• and
• (c) after the step (b), separating the plurality of chip regions from each other by cutting the cutting region of the semiconductor wafer,
• wherein the step (b) has the steps of:
• (b1) forming the groove in the back surface such that the groove is extended in a first direction across the first power transistor formation region and the second power transistor formation region in plan view;
• (b2) after the step (b1), filling the inside of the groove with a conductor film by forming the conductor film on the back surface in which the groove is formed;
• and
• (b3) after the step (b2), exposing the back surface of the semiconductor wafer by removing a portion of the conductor film that is located outside the groove.