A vertical wafer heat treatment apparatus for for forming a film on and dry etching a plurality of wafers stored in a wafer boat. The apparatus has at least first and second load lock chambers connected by a gate. Each load lock has an inert gas independently introduced therein and exhausted therefrom. The load lock chambers are vertically connected between two separate process containers. An elevator is provided in the first load lock chamber to transfer a wafer boat into and out of the first container. A transfer means is provided in the second load lock to transfer wafers into and out of a wafer boat.