Semiconductor device and manufacturing method thereof

A method of forming a semiconductor device, comprising:

• forming a photoresist layer on a substrate;
• forming a P-type heavily doped region in the substrate by using the photoresist layer as mask;
• forming a sacrificial layer on the substrate and covering the P-type heavily doped region;
• performing a first wet etching process to pattern the sacrificial layer, so that a sidewall of the sacrificial layer is above the substrate inside the P-type heavily doped region;
• forming an N-type heavily doped region in the substrate by using the sacrificial layer as mask, wherein the N-type heavily doped region is adjacent to the P-type heavily doped region;
• performing a second wet etching process to retract the sidewall of the sacrificial layer to the substrate inside the N-type heavily doped region;
• forming a P-type lightly doped region in the substrate by using the sacrificial layer as mask, wherein the P-type lightly doped region is adjacent to the N-type heavily doped region, and is in contact with a bottom of the P-type heavily doped region and a bottom of the N-type heavily doped region;
• and
• removing the sacrificial layer.