Patent ID: 6919607
Filing Date: 2005-07-19
Classification: H01L

Abstract:
1. A 2-bit mask ROM device, comprising: a substrate; a gate structure disposed on the substrate; a coding region, located in the substrate beside a side of the gate structure, wherein presence or absence of dopants in the coding region determines “1” state or “0” state respectively; at least one spacer disposed on a sidewall of the gate structure; a buried drain region located in the substrate beside a side of the spacer, wherein the buried drain region and the coding region further comprises a buffer region in between, wherein dopant type of the buffer region and dopant type of the coding region are the same, and the buffer region has a dopant concentration lower than that of the coding region; an insulation structure, positioned on the substrate above the buried drain region; and a word line, disposed on a surface of the gate structure.