A method of forming first and second fin field effect transistors (finFETs) on a substrate includes forming first and second fin structures of the first and second finFETs, respectively, on the substrate. The first and second fin structures have respective first and second vertical dimensions that are about equal to each other. The method further includes modifying the first fin structure such that the first vertical dimension of the first fin structure is smaller than the second vertical dimension of the second fin structure and depositing a dielectric layer on the modified first fin structure and the second fin structure. The method further includes forming a polysilicon structure on the dielectric layer and selectively forming a spacer on a sidewall of the polysilicon structure.