A transistor is formed by applying modifier coatings to source and drain contacts and/or to the channel region between those contacts. The modifier coatings are selected to adjust the surface energy pattern in the source/drain/channel region such that semiconductor printing fluid is not drawn away from the channel region. For example, the modifier coatings for the contacts can be selected to have substantially the same surface energy as the modifier coating for the channel region. Semiconductor printing fluid deposited on the channel region therefore settles in place (due to the lack of a surface energy differential) and forms a relatively thick active semiconductor region between the contacts. Alternatively, the modifier coatings can be selected to have lower surface energies than the modifier coating in the channel region, which actually causes semiconductor printing fluid to be drawn towards the channel region.