Sidewall morphology on three-dimensional (313) tungsten structures grown with focused ion beam-induced chemical vapor deposition (FIB-CVD) using tungsten hexacarbonyl [W(CO)(6)] was improved with a milling process by using FIB treatment subsequent to growth. As a result, Young's modulus was measured at 300 GPa at maximum and density was measured at 13.0 x 10(3) kg/m(3). Young's modulus increased 35% after heat treatment at 600degreesC in a vacuum while density did not change. Transmission electron microscopy revealed crystallization of tungsten trioxide after the heat treatment. (C) 2003 American Vacuum Society.