A semiconductor device includes lower circuit patterns on a lower substrate; lower bonding patterns on the lower circuit patterns, the lower bonding patterns including a conductive material and being electrically connected to the lower circuit patterns; upper bonding patterns on and contacting the lower bonding patterns, and including a conductive material; a passive device on the upper bonding patterns, and including a conductive material and contacting one of the upper bonding patterns; a gate electrode structure on the passive device, and including gate electrodes spaced apart from each other in a first direction, each of which extends in a second direction, and extension lengths in the second direction of the gate electrodes increasing from a lowermost level toward an uppermost level in a stepwise manner; a channel extending through at least a portion of the gate electrode structure; and an upper substrate on the channel.