Patent ID: 6847084

Claim:
A semiconductor device comprising: a semiconductor substrate; a first circuit formed on the semiconductor substrate, the first circuit including first and second field-effect transistors, the first field-effect transistor comprising: a first source region and a first drain region formed apart from each other on a surface of the semiconductor substrate; a first gate insulation film formed between the first source region and the first drain region; and a first gate electrode formed on the first gate insulation film, the second field-effect transistor comprising: a second source region and a second drain region formed apart from each other and apart from the first field-effect transistor on the surface of the semiconductor substrate; a second gate insulation film formed between the second source region and the second drain region; and a second gate electrode formed on the second gate insulation film, the first drain region of the first field-effect transistor accompanying a first load capacitance, the second drain region of the second field-effect transistor accompanying a second load capacitance which is smaller than the first load capacitance, and the first gate insulation film of the first field-effect transistor having an average relative dielectric constant higher than that of the second gate insulation film of the second field-effect transistor, and a second circuit coupled to the first circuit as an input/output portion of the first circuit and powered by a voltage higher than that for the first circuit.