A thermal infrared detector includes a substrate; a temperature sensor having electrical characteristics changed in accordance with changes in temperature caused by infrared absorption; heat-insulating supporting legs supporting and thermally insulating the temperature sensor and serving as signal lines for reading out electrical signals from the temperature sensor; and an infrared absorption layer in thermal contact the temperature sensor. Each of the temperature sensor, the heat-insulating supporting legs, and the infrared absorption layer is in a different plane and the planes are spatially separated from each other.
A thermal infrared sensor device includes a substrate having a concave portion, a temperature detecting portion connected to the substrate via a supporting leg held at an upper portion of a space within the concave portion, an infrared reflecting film covering at least a portion of the supporting leg without being thermally connected to the temperature detecting portion, and an absorbing hood portion held opposite the infrared reflecting film and thermally connected to the temperature detecting portion, without being thermally connected to the infrared reflecting film, and extending laterally, in a plate shape, covering at least a portion of the infrared reflecting film.