Infrared detector and solid state image sensor having the same

An infrared detector includes: a readout wiring portion provided on a semiconductor substrate; a support structure portion disposed over a concave portion formed in a surface portion of the semiconductor substrate, the support structure portion having connection wiring connected electrically to the readout wiring portion; and a cell portion disposed over the concave portion and supported by the support structure portion. The cell portion includes: an infrared absorption layer absorbing incident infrared rays; and a plurality of thermoelectric conversion elements connected electrically to the support structure portion and insulated electrically from the infrared absorption layer to generate an electric signal by detecting a temperature change of the cell portion, each of the thermoelectric conversion elements includes a semiconductor layer, a p-type silicon layer and an n-type silicon layer formed with a space between them in the semiconductor layer, and a polysilicon layer formed on the semiconductor layer between the p-type silicon layer and the n-type silicon layer.