Patent ID: 9564520
Date: 2017-02-07
CPC Classifications: H01L

Claim:
1. A method of forming a semiconductor device, comprising: providing a substrate having a first area and a second area; forming a sacrificial oxide layer on the substrate in the first and second areas; forming a photoresist mask on the sacrificial oxide layer to expose the first area and cover the second area; using the photoresist mask as a mask layer, by a wet etching process, simultaneously removing the sacrificial oxide layer in the first area and an edge portion of the sacrificial oxide layer in the second area covered by the photoresist mask, wherein the sacrificial oxide layer remained in the second area has a sidewall with a slope smaller than 40 degrees; forming an oxide-nitride-oxide (ONO) layer over the substrate in the first and second areas; removing the sacrificial oxide layer and the ONO layer formed thereon in the second area, so that the ONO layer remained in the first area forms a first gate insulating layer on the substrate in the first area; and forming a second gate insulating layer on the substrate in the second area.