A perpendicular magnetic recording (PMR) writer is configured to magnetically record data on a rotatable disk surface. The PMR writer including a pole tip, side shields, an air-bearing surface (ABS) region, a yoke region comprising Silicon Dioxide (SiO2), side gaps and a plurality of throat regions. The side gaps are arranged respectively between the pole tip and the side shields and include SiO2. A side gap width of the plurality of throat regions increases with a side shield throat height above the ABS region for each of the throat regions. The side gap width has a different width variation in each of the throat regions.