Novel quantum nano-structures which consist of quantum dots connected with quantum wires through tunneling barriers have successfully been fabricated using selective area metalorganic vapor phase epitaxy (SA-MOVPE) and have been applied to form single electron devices. GaAs/AlGaAs modulation doped heterostructures are grown on a GaAs (001) substrate partially masked with SiNx. A quasi-1 dimensional electron gas (Q-1DEG) is formed in a narrow wire-like opening, which has two prominences and a dent to modulate the channel width. From the transport properties, we confirm that a quantum dot and quantum wires connected through tunneling barriers, that is, a single electron transistor structure, is naturally formed in the part of the channel with modulated width. We will discuss the mechanism by which the dot and tunnel barriers are formed by SA-MOVPE.