Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, the method comprising the following sequential steps:

• (a) forming a deposition structure including a pad oxide film and a pad nitride film which exposes a device separating region of a semiconductor substrate;
• (b) etching the semiconductor substrate using the pad oxide film as an etching mask to form a trench which defines an active region;
• (c) after said step (b) forming an insulating film for separating the device, wherein the insulating film fills the trench;
• (d) planarizing the insulating film until the pad nitride film is exposed to form a device separating film;
• (e) etching the pad nitride film using a first gate mask such that a residual pad nitride film is formed over a recess gate region to be formed in the active region, wherein the first gate mask defines a line-type recess gate region;
• (f) forming a first hard mask layer over the residual pad nitride film and the pad oxide film;
• (g) planarizing the first hard mask layer until the residual pad nitride film is exposed to form a first hard mask pattern;
• (h) removing the residual pad nitride film, the pad oxide film and the semiconductor substrate to form the recess gate region using the first hard mask pattern as an etching mask to form a recess;
• (j) removing the first hard mask pattern and the pad oxide film;
• (j) forming a gate oxide film over the exposed semiconductor substrate;
• (k) forming a gate conductive layer over the gate oxide film, wherein the gate conductive layer fills the recess;
• (l) forming a gate hard mask layer over the gate conductive layer;
• and
• (m) patterning the gate hard mask layer and the gate conductive layer using a gate mask as an etching mask to form a gate.