Methods of making power semiconductor devices with thick bottom oxide layer

摘要

A method of manufacturing a semiconductor device having a charge control trench and an active control trench with a thick oxide bottom includes forming a drift region, a well region extending above the drift region, an active trench extending through the well region and into the drift region, a charge control trench extending deeper into the drift region than the active trench, an oxide film that fills the active trench, the charge control trench and covers a top surface of the substrate, an electrode in the active trench, and source regions. The method also includes etching the oxide film off the top surface of the substrate and inside the active trench to leave a substantially flat layer of thick oxide having a target thickness at the bottom of the active trench.