A memory device includes a first memory block. The first memory block includes a first memory sub-array and a first interface portion disposed next to the first memory sub-array. The first interface portion has a plurality of first control structures formed as a first staircase profile. The first memory block further includes a plurality of first interconnect structures landing on a corresponding one of the plurality of first control structures, and a plurality of second interconnect structures configured to electrically couple a corresponding one of the plurality of first interconnect structures to a first transistor. The memory device further includes a first test structure and a second test structure disposed next to the first memory block, each configured to simulate electrical connections of the plurality of second interconnect structures. The first and second test structures are electrically coupled to each other and are electrically isolated form the first memory block.