A write element for perpendicular recording in a data storage system is fabricated to maintain the thickness of a side shield at both edges of a pole P3, and to form the pole P3 in a trapezoidal shape. Forming a side shield around the pole P3 removes stray fields, creating a quiet, noise-free write element and preventing side erasure. The fabrication method utilizes a magnetic buffer layer to protect a shield gap during trim of the pole P3, and thus to provide the shield gap with a uniform thickness. The magnetic buffer layer also protects the shield gap and pole P3 when the top hard mask is removed. Consequently, the write field is made uniform across the track width. The fabrication method uses a metal in the shield gap to improve the pole geometry after pole trim and to provide a uniform edge to the pole P3.