A semiconductor device includes a first semiconductor chip that includes a first conductive pad whose top surface is exposed; and a second semiconductor chip that includes a second conductive pad whose top surface is exposed and in contact with at least a portion of the top surface of the first conductive pad. The first semiconductor chip may include a first diffusion barrier in contact with a bottom surface of the first conductive pad, and a second diffusion barrier in contact with a lateral surface of the first conductive pad, and the first diffusion barrier and the second diffusion barrier may include different materials from each other.