There is provided a small-type semiconductor integrated circuit whose circuit area is small and whose wiring length is short. The semiconductor integrated circuit is constructed in a multi-layer structure and is provided with a first semiconductor layer, a first semiconductor layer transistor formed in the first semiconductor layer, a wiring layer which is deposited on the first semiconductor layer and in which metal wires are formed, a second semiconductor layer deposited on the wiring layer and a second semiconductor layer transistor formed in the second semiconductor layer. It is noted that insulation of a gate insulating film of the first semiconductor layer transistor is almost equal with that of a gate insulating film of the second semiconductor layer transistor and the gate insulating film of the second semiconductor layer transistor is formed by means of radical oxidation or radical nitridation.