A semiconductor device includes an insulating substrate, a polysilicon layer formed on the insulating substrate, a first-gate-insulating layer formed on the polysilicon layer, a first metal layer formed on the first-gate-insulating layer, an oxide-semiconductor layer formed on the first-gate-insulating layer, a second-gate-insulating layer formed on the oxide-semiconductor layer, a second metal layer formed on the second-gate-insulating layer, a first insulating interlayer formed on the second metal layer, a third metal layer formed on the first insulating interlayer, a first top gate planar type thin film transistor in which the polysilicon layer serves as a channel and which has a source, a drain and a gate, and a second top gate planar self-aligned type thin film transistor in which the oxide-semiconductor layer serves as a channel and which has a source, a drain and a gate, wherein the gate of the first top gate planar type thin film transistor is made of a first metal layer, the gate of the second top gate planar self-aligned type thin film transistor is made of the second metal layer, the source and the drain of the first top gate planar type thin film transistor and the source and the drain of the second top gate planar self-aligned type thin film transistor are made of the third metal layer, and the source or the drain of the first top gate planar type thin film transistor and the gate of the second top gate planar self-aligned type thin film transistor are electrically connected to each other.