A photodetection module includes a photodetector and a fixing member. The photodetector includes a semiconductor substrate, a mesa portion, a first contact layer, a second contact layer, and a first electrode formed in a planar shape on a major surface of the semiconductor substrate, and electrically connected to one of the first contact layer and the second contact layer. The fixing member includes an insulating substrate, and a first wiring formed in a planar shape on a major surface of the insulating substrate. A recessed portion is formed in the major surface of the insulating substrate, and at least a part of the mesa portion is disposed inside the recessed portion. The first electrode is electrically connected to the first wiring in a state where the first electrode is in surface contact with the first wiring.

A circuit structure and a method of manufacturing a circuit structure are provided. The circuit structure includes a first metal line and a second metal line. The second metal line is disposed over the first metal line. At least one air gap is disposed between the first metal line and the second metal line.