An advanced bulk CMOS process has been developed using SEG (Selective Epitaxial Growth) isolation technique and high impurity concentration substrate, in order to suppress latch-up phenomenon. CMOS devices are fabricated on epitiaxial layer, which is selectively grown over p-type silicon substrate surrounded by a 2 µm thick SiO2insulator, using a reduced pressure SiH2Cl2-H2-HCl system. P-channel devices are formed in an n-well, having 3 µm depth. The gate oxide is 20 nm thick. 400 nm thick phosphorus-doped polysilicon is used as a gate electrode. The transition region for autodoping from p+- substrate to the epitaxial layer is less than 1 µm. This isolation combined with low resistivity substrate is effective to reduce latch-up for CMOS circuits. Submicron gate CMOS operation is confirmed using SEG isolation technique.