The self-aligned fabrication of diamond-coated silicon field emitters was performed by a selective chemical vapor deposition of diamond on p-type (100)-oriented silicon followed by argon ion milling of the patterned structures. Field emission measurements of as-prepared and thermally as well as hydrogen plasma treated diamond-coated silicon emitter arrays with base diameters ranged from 1.2 to 10 mu m were carried out by field emission scanning microscopy with Crm resolution. The applied electrical surface field has been varied between 20 and 250 MV m(-1). It was found that the combination of thermal and hydrogen plasma treatments can substantially improve the electron emission of diamond-coated silicon emitters. Depending on their base diameter the held emitters demonstrated stable electron emission for E > 80-120 MV m(-1). Fowler-Nordheim analysis for arrays and individual field emitters was performed.