Patent ID: 8557687

Claim:
A method for forming a semiconductor device comprising the steps of: introducing hydrogen and a deposition gas containing silicon or germanium into a treatment chamber, periodically increasing and decreasing a flow rate of the deposition gas, generating a plasma in the treatment chamber by supplying high-frequency power so that a microcrystalline semiconductor film is formed over a substrate, and manufacturing a thin film transistor comprising the microcrystalline semiconductor film, wherein a flow rate of the hydrogen is constant, wherein the step of periodically increasing and decreasing the flow rate of the deposition gas comprises a first step and a second step alternately and repeatedly, wherein the first step is a step of increasing the flow rate of the deposition gas from a first flow rate to a second flow rate, wherein the second step is a step of decreasing the flow rate of the deposition gas from the second flow rate to the first flow rate, and wherein the first flow rate is a positive value.