A semiconductor structure includes a source feature, a drain feature, one or more channel layers connecting the source feature and the drain feature, and a gate structure between the source feature and the drain feature. The gate structure engages each of the one or more channel layers. The semiconductor structure further includes a first source silicide feature over the source feature, a source contact over the first source silicide feature, a second source silicide feature under the source feature, a via under the second source silicide feature, and a power rail under the via. The first and the second source silicide features fully surround the source feature in a cross-sectional view. The power rail is a backside power rail.