preparing a semiconductor wafer having a first main surface and including a semiconductor region of a first conductivity type; and

implanting impurity ions into the semiconductor wafer to form a semiconductor substrate that has the first main surface and a second main surface facing the first main surface and forms an avalanche photodiode and a temperature compensation diode so as to be spaced apart from each other when viewed from a direction perpendicular to the first main surface,

wherein the light detection device is a light detection device which includes the semiconductor substrate and in which a voltage corresponding to a breakdown voltage applied to the temperature compensation diode is applied to the avalanche photodiode as a bias voltage to provide temperature compensation for a multiplication factor of the avalanche photodiode, and

the forming the semiconductor substrate includes:

a first ion implantation process of implanting impurity ions into a first portion and a second portion in the semiconductor wafer to form, in each of the first and second portions, a first semiconductor layer of a second conductivity type different from the first conductivity type and a second semiconductor layer of the first conductivity type, the first portion and the second portion being spaced apart from each other when viewed from the direction perpendicular to the first main surface, the second semiconductor layer being located between the semiconductor region and the first semiconductor layer and having a higher impurity concentration than the semiconductor region; and

a second ion implantation process of further implanting impurity ions into the second semiconductor layer in the first portion.