Patent ID: 8357572

Claim:
A method for manufacturing a semiconductor device, the method comprising: forming an active region on a semiconductor substrate, the active region being elongated in a first direction; forming a recess in a channel region of the active region so that a width in the first direction of a lower part of the recess is greater than that of an upper part of the recess; forming a device isolation structure defining the active region, wherein forming the device isolation structure comprises: etching opposing portions extending in a second direction, which is substantially orthogonal to the first direction, from the lower part of the recess, each etched portion having a depth lower than an upper surface of the active region, wherein the lower part of the recess has a width in the second direction that is greater than a width of the upper part of the recess in the second direction, and wherein a minimum width of the upper part of the recess in the second direction is greater than a maximum width of the active region in the recess; forming a gate insulating film over portions of the active region in the recess; and forming a gate electrode over portions of the gate insulating film and filling the recess and the etched portions.