A semiconductor device with improved temperature detection accuracy includes a coefficient calculation circuitry which calculates a plurality of N-th order coefficients, where N is an integer equal to or greater than one, of a correction function as an N-th order approximation of a characteristic function which relates temperature data measured by the temperature sensor and the actual temperature. The coefficient calculation circuitry uses N+1 pieces of the temperature data including a theoretical value at absolute zero in the characteristic function and N measured values of the temperature data measured by the temperature sensor unit at N points of temperature. A corrected temperatures are output using the correction function with the calculated coefficients and measured temperature values.