A heat dissipation device includes a first casing and a second casing coupled to the first casing. The second casing includes a body having an inner surface and an outer surface opposite the inner surface, and a first portion and a second portion, each of the first and second portions having a different cross-sectional area. The heat dissipation device further includes a plurality of columns on the inner surface, and a first wick structure disposed on the inner surface and in the first portion and the second portion.