We present the results of detailed chemical and structural characterization of the VO2/Al/Si(100) thin film heterostructures fabricated by chemical vapor deposition and physical vapor deposition methods. The presence of the thermochromic behavior in the VO2 layer around 68°C and its correlation with the layer composition and structure are discussed. The study compares the structural and chemical properties of the two types of thin VO2 layers: one which exhibits a metal-insulator phase transition around 68°C, and another which fails to undergo the temperature-induced transition. The study of interfaces was carried out by transmission electron microscopy, and showed the existence of an aluminum oxide interfacial layer between VO2 and Al for the samples with the metal-insulator phase transition. The smooth VO2/Al interface and the presence of more than one VO2 monoclinic polytypes were observed for the CVD films exhibiting no phase transition.