| CPC H01L 29/4236 (2013.01) [G11C 5/063 (2013.01); H01L 29/401 (2013.01); H01L 29/4916 (2013.01); H01L 29/495 (2013.01); H10B 12/488 (2023.02)] | 17 Claims |

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1. A semiconductor device, comprising:
a semiconductor substrate having an active region; and
a word line structure disposed in the active region of the semiconductor substrate, the word line structure comprising:
a first work function layer;
a second work function layer on the first work function layer;
a buffer structure having a bottom buffer layer between the first work function layer and the second work function layer; and
a barrier layer having a top portion between the bottom buffer layer of the buffer structure and the first work function layer;
wherein the word line structure further comprises:
a dielectric layer surrounding the buffer structure, the barrier layer, the first work function layer and the second work function layer, wherein the buffer structure and the dielectric layer comprise a same material.
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