4H-SiC epilayers are grown in a vertical hot-wall reactor with an inner susceptor configuration. Reduction of micropipe density can be achieved by chemical vapor deposition (CVD) growth using SiH4 and C3H8 as source gases. This technique involves dissociation of micropipes into elementary screw dislocations by growth of a micropipe stop (MS) layer. The most important parameter to control micropipe dissociation was found to be C/Si ratios of the source gases. A high probability of micropipe dissociation is obtained at a relatively low C/Si ratio. Meanwhile we have succeeded in closing more than 99.6% of micropipes in a commercial 4H-SiC substrate by a single growth run. Low-doped active layers are grown at a relatively high C/Si ratio onto MS layers without coalescing of elementary screw dislocations. A large Schottky barrier diode (SBD) with a diameter of 11.2 mmphi was fabricated using this technique. We also discuss growth of very thick 4H-SiC epilayers at a high growth rate and other issues.