Patent ID: 7601588

Claim:
A method of forming an isolation layer on a substrate, comprising: forming a hard mask pattern on the substrate; etching the substrate using the hard mask pattern as an etching mask, thereby forming a trench at a surface portion of the substrate; forming a first insulation layer on top and side surfaces of the hard mask pattern and on inner surfaces of the trench, thereby forming a first recess including a portion of the trench and a portion of a space between the hard mask patterns; forming a second insulation layer on the first insulation layer to a thickness to fill up the first recess an etching rate of the second insulation layer being different from that of the first insulation layer; partially removing the first and the second insulation layers from the substrate such that the first and second insulation layers only remain in the trench and the space, thereby forming a preliminary isolation layer having a first insulation pattern and a second insulation pattern in the trench and the space; and performing an etching process against the preliminary isolation layer and the hard mask pattern such that the hard mask pattern is removed from the substrate to expose an active region of the substrate and the second insulation pattern is etched off more than the first insulation pattern to form a second recess surrounded by the first insulation pattern, thereby forming the isolation layer in the trench in such a configuration that a bottom surface of the second recess is at a position lower than a top surface of the substrate and a top surface of the first insulation layer is at a position higher than the top surface of the substrate.