A thermal infrared sensor is provided in a housing with optics and a chip with thermoelements on a membrane. The membrane spans a frame-shaped support body that is a good heat conductor, and the support body has vertical or approximately vertical walls. The thermopile sensor structure consists of a few long thermoelements per sensor cell. The thermoelements being arranged on connecting webs that connect together hot contacts on an absorber layer to cold contacts of the thermoelements. The membrane is suspended by one or more connecting webs and has, on both sides of the long thermoelements, narrow slits that separate the connecting webs from both the central region and also the support body. At least the central region is covered by the absorber layer.