A bonded semiconductor structure includes a first device wafer and a second device wafer. The first device wafer includes a first insulating layer, a first device layer on the first insulating layer, and a first bonding layer on the first device layer. The second device wafer includes a second insulating layer, a second device layer on a first side of the second insulating layer, and a second bonding layer on the second device layer. The second device layer includes a second device region and a second transistor in the second device region. The second device wafer is bonded to the first device wafer by bonding the second bonding layer with the first bonding layer. A shielding structure is on a second side of the second insulating layer opposite to the first side and vertically overlapped with the second device region.