Semiconductor device

A semiconductor device comprising:

• a substrate having a first side and a second side opposite to the first side;
• a first optical element at the first side of the substrate;
• a semiconductor stack on the substrate and comprising:
• a first reflective structure;
• a second reflective structure;
• a cavity region between the first reflective structure and the second reflective structure and having a first surface and a second surface opposite to the first surface;
• and
• a confinement layer in one of the second reflective structure and the first reflective structure;
• a first electrode on the first surface;
• and
• a second electrode on the first surface,
• wherein the substrate, the first optical element and the semiconductor stack are overlapped with each other in a thickness direction of the cavity region, and
• wherein the semiconductor device emits a coherent radiation.