SEMICONDUCTOR DEVICE

PURPOSE:To obtain a high performance C-MOS.IC by a method wherein an N channel transistor and a P channel transistor are built in different substrates and the transistors enjoy a roughly equal mobility or the mobility ratio between the two is devised to approach the quantity one. CONSTITUTION:An N type Ge substrate 22 is selectivity grown on a P type Si substrate 20 by the vapor deposition method. An N channel MOS transistor 21 is built on the substrate 20 and a P channel MOS transistor 23 is built on the substrate 22. Next, source regions 24 and 24' are respectively connected to a ground terminal 25 and a power source terminal 26, drain regions 27 and 27' jointly to an output terminal 29, gate electrodes 28 and 28' jointly to an output terminal 29', constituting an inverter circuit. Mobility is rough balanced between the two transistors, 1,350cm /V.sec for the transistor 21 and 1,900cm /V.sec for the transistor 23. Inductance is also roughly balanced between the two transistors and the gate oxide films can be smaller in area. Parasitic capacity decreases, which results in a high speed switching.