Patent ID: 7498226

Claim:
A method for fabricating a semiconductor device, the method comprising: forming an organic bottom anti-reflective coating (BARC) layer over a substrate; forming a patterned mask over the organic BARC layer that exposes selected portions of the organic BARC layer; etching the exposed portions of the organic BARC layer using an etch gas having a high selectivity to the substrate until the substrate underlying the exposed portions of the organic BARC layer is substantially exposed; etching the exposed portions of the substrate to form a plurality of recessed active regions; removing the mask and the organic BARC layer to expose a plurality of protruding active regions defined by the recessed active regions; forming a gate insulation layer over the recessed active regions and the protruding active regions; and forming asymmetric step-structured gates over the gate insulation layer, each gate extending over the corresponding recessed active region and the corresponding protruding active region, wherein the substrate includes a high effective field oxide height (EFH) region and a low EFH region, wherein the substrate is etched to substantially the same depth at the high EFH region and the low EFH region to form the active recessed regions at the high EFH region and the low EFH region.