Patent ID: 8143127

Claim:
A method for manufacturing a semiconductor device, comprising the steps of: forming a device isolation structure in a silicon substrate, which delimits an active region having a pair of gate forming areas, a drain forming area between the gate forming areas, and source forming areas outside the gate forming areas; forming a hard mask on the silicon substrate including the device isolation structure to have openings for exposing the gate forming areas; defining first grooves by etching the exposed gate forming areas; forming spacers on the sidewalls of the first grooves including the openings of the hard mask facing the source forming areas; defining second grooves under the first grooves by etching exposed bottom portions of the first grooves using the hard mask including the spacers as an etch mask; removing the spacers and the hard mask; forming an oxide layer on the surface of the substrate including the first and second grooves to expose the lower end portions of the sidewalls of the second grooves, which face the source forming areas; defining asymmetric bulb-type grooves including the first and second grooves by isotropically etching the exposed lower end portions of the sidewalls of the second grooves, thereby forming bulb-type grooves; removing the oxide layer; forming asymmetric bulb-type recess gates in the asymmetric bulb-type grooves; and forming source and drain areas on the surface of the substrate on both sides of the asymmetric bulb-type recess gates, wherein the step of forming spacers comprises: forming a spacer layer on the hard mask including the first grooves; forming spacers on both sidewalls of the first grooves including the openings of the hard mask by anisotropically etching the spacer layer; forming a photoresist pattern on the resultant substrate having the spacers formed on both sidewalls of the first grooves including the openings of the hard mask, such that spacers, which are formed on sidewalls of the first grooves facing the source forming areas, are covered by the photoresist pattern, and spacers, which are formed on sidewalls of the first grooves facing the drain forming area, are exposed; removing the exposed spacers formed on the sidewalls of the first grooves facing the drain forming area; and removing the photoresist pattern.