Provided is a method for manufacturing a semiconductor device, including: forming a conductive layer on the first dielectric layer; forming a recess in the conductive layer; performing a first etching process to round a top corner of the recess; performing a second etching process to remove the conductive layer exposed from a bottom surface of the recess and thereby forming an opening having a rounding top corner in the conductive layer; and forming a second dielectric layer in the opening.