Before revision:  The obtained closed formulas fit well the historical data on global corporate defaults and demonstrate the split behavior of credit spreads for bonds  in different categories of speculative-grade ratings with varying  time to maturity.
After revision:  The obtained closed formulas fit well the historical data on global corporate defaults and demonstrate the split behavior of credit spreads for bonds in different categories of speculative-grade ratings with varying time to maturity. Introduction of the finite rate of default at the boundary improves valuation of credit risk for short time horizons, which is the key advantage of the proposed model. We also consider the influence of uncertainty in the initial distance to the default barrier on the outcome of the model and demonstrate that this additional source of incomplete information may be responsible for non-zero credit spreads for bonds with very short time to maturity.