Patent attributes
A semiconductor device has a semiconductor substrate in which first and second wells are formed. The substrate and wells are of the same conductivity type, but the second well has a higher impurity concentration than the first well. High-voltage MOS transistors are formed in the first well, and a low-voltage MOS transistor is formed in the second well. The high-voltage MOS transistors include a first transistor having a gate oxide layer with a first thickness and a second transistor having a gate oxide layer with a second thickness less than the first thickness. The low-voltage MOS transistor has a third gate oxide layer with a third thickness less than the first thickness. The second high-voltage MOS transistor provides efficient current conduction.
