Patent ID: 8062954
Filing Date: 2011-11-22
Classification: H01L

Abstract:
1. A method for manufacturing a field plate in a trench in a substrate, wherein the trench is formed in a first main surface of the substrate, the method comprising: growing a field oxide layer over the first main surface of the substrate and side walls of the trench; depositing polysilicon at least in the trench; etching the polysilicon, wherein the polysilicon is etched in the trench up to a first level above a bottom of the trench; thermally oxidizing the polysilicon in the trench and the field oxide layer on side walls of the trench, wherein the polysilicon oxide has a growth rate that is higher than a growth rate of the oxide on the side wall of the trench; etching the polysilicon oxide in the trench and the oxide on the side walls of the trench, wherein the polysilicon oxide is removed by etching up to a top side of the polysilicon, such that the polysilicon remains up to a second level from the bottom of the trench, and the oxide on the side walls of the trench is etched to a third level from the bottom of the trench, the third level being as far or farther from the bottom of the trench than the second level; and forming a gate oxide layer in the trench and on the first main surface of the substrate, wherein the polysilicon remaining in the trench below the gate oxide layer forms a field plate.