The method 1, wherein {HEAD ~ the first depth} is no less than 50% and no more than 80% of a thickness of {TAIL ~ the interlayer dielectric layer} 
The method 1 , wherein { HEAD ~ the first depth } is no less than 50 % and no more than 80 % of a thickness of { TAIL ~ the interlayer dielectric layer }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL