A thin film transistor array panel includes a plurality of pixels on a substrate. Each pixel of the plurality of pixels includes a driving and a switching thin film transistor. The driving thin film transistor includes a first semiconductor including first source and drain regions, a first gate electrode overlapping the first semiconductor, a gate insulating layer between the first semiconductor and the first gate electrode, an oxide layer between the first semiconductor and the gate insulating layer, and first source and drain electrodes. The switching thin film transistor includes a second semiconductor including second source and drain regions, a second gate electrode overlapping the second semiconductor, and second source and drain electrodes. The switching thin film transistor includes the gate insulating layer between the second semiconductor and the second gate electrode. The gate insulating layer contacts an upper portion of the second semiconductor.