| CPC H10D 30/6755 (2025.01) [H01L 24/08 (2013.01); H10B 12/05 (2023.02); H10B 12/50 (2023.02); H10D 30/475 (2025.01); H10D 30/477 (2025.01); H10D 30/478 (2025.01); H10D 30/6757 (2025.01); H10D 62/80 (2025.01); H10D 99/00 (2025.01); H01L 2224/08145 (2013.01)] | 20 Claims |

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1. A semiconductor memory device, comprising:
a bit line extending in a first direction;
a channel pattern on the bit line, the channel pattern including a first oxide semiconductor layer contacting the bit line and a second oxide semiconductor layer on the first oxide semiconductor layer, each of the first and second oxide semiconductor layers including a horizontal part parallel to the bit line and a first vertical part and a second vertical part that vertically protrude from the horizontal part;
a first word line and a second word line that are between the first and second vertical parts of the second oxide semiconductor layer and are on the horizontal part of the second oxide semiconductor layer, the first and second word lines running across the bit line; and
a gate dielectric pattern between the channel pattern and the first and second word lines, the gate dielectric pattern on the first and second vertical parts,
wherein a thickness of the second oxide semiconductor layer is greater than a thickness of the first oxide semiconductor layer.
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