A semiconductor device includes an analog-to-digital converter configured to perform a process of sampling an analog input signal and a successive-approximation process, execute an AD conversion process, and output a digital output signal. The AD converter includes an upper DAC, a redundant DAC, a lower DAC, a comparator configured to compare a comparative reference voltage and output voltages of the upper DAC, the redundant DAC and the lower DAC, a control circuit configured to control successive approximations by the upper DAC, the redundant DAC and the lower DAC based on the comparison result of the comparator, and generate a digital output signal, and a correction circuit. The correction circuit includes an error correction circuit configured to correct an error of the upper bit with the redundant bit, and an averaging circuit configured to calculate an average value of conversion values of a plurality of the lower bits supplied multiple times.