Semiconductor device and method for manufacturing semiconductor device

A semiconductor device comprising:

• a semiconductor element;
• a submount on which the semiconductor element is mounted, wherein the submount has a first surface on which the semiconductor element is mounted, a second surface located on a side opposite the first surface, and a lateral surface located between the first surface and the second surface, and wherein the submount comprises:
• a groove located at the second surface,
• a heat dissipation portion located at the second surface, and
• an electrode pattern located at the first surface;
• a package substrate on which the submount is mounted;
• a first joint member that physically joins the heat dissipation portion to the package substrate;
• and
• a connection portion located on the side surface, wherein the connection portion electrically connects the electrode pattern and the package substrate, and the connection portion comprises a second joint member;
• wherein the heat dissipation portion and the connection portion are separated by the groove and are electrically insulated from each other.